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   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/stat.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/smp_lock.h>
  32 #include <linux/swap.h>
  33 #include <linux/string.h>
  34 #include <linux/init.h>
  35 #include <linux/pagemap.h>
  36 #include <linux/highmem.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/key.h>
  39 #include <linux/personality.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/utsname.h>
  42 #include <linux/pid_namespace.h>
  43 #include <linux/module.h>
  44 #include <linux/namei.h>
  45 #include <linux/proc_fs.h>
  46 #include <linux/mount.h>
  47 #include <linux/security.h>
  48 #include <linux/ima.h>
  49 #include <linux/syscalls.h>
  50 #include <linux/tsacct_kern.h>
  51 #include <linux/cn_proc.h>
  52 #include <linux/audit.h>
  53 #include <linux/tracehook.h>
  54 #include <linux/kmod.h>
  55 #include <linux/fsnotify.h>
  56 #include <linux/fs_struct.h>
  57
  58 #include <asm/uaccess.h>
  59 #include <asm/mmu_context.h>
  60 #include <asm/tlb.h>
  61 #include "internal.h"
  62
  63 int core_uses_pid;
  64 char core_pattern[CORENAME_MAX_SIZE] = "core";
  65 int suid_dumpable = 0;
  66
  67 /* The maximal length of core_pattern is also specified in sysctl.c */
  68
  69 static LIST_HEAD(formats);
  70 static DEFINE_RWLOCK(binfmt_lock);
  71
  72 int __register_binfmt(struct linux_binfmt * fmt, int insert)
  73 {
  74         if (!fmt)
  75                 return -EINVAL;
  76         write_lock(&binfmt_lock);
  77         insert ? list_add(&fmt->lh, &formats) :
  78                  list_add_tail(&fmt->lh, &formats);
  79         write_unlock(&binfmt_lock);
  80         return 0;
  81 }
  82
  83 EXPORT_SYMBOL(__register_binfmt);
  84
  85 void unregister_binfmt(struct linux_binfmt * fmt)
  86 {
  87         write_lock(&binfmt_lock);
  88         list_del(&fmt->lh);
  89         write_unlock(&binfmt_lock);
  90 }
  91
  92 EXPORT_SYMBOL(unregister_binfmt);
  93
  94 static inline void put_binfmt(struct linux_binfmt * fmt)
  95 {
  96         module_put(fmt->module);
  97 }
  98
  99 /*
 100  * Note that a shared library must be both readable and executable due to
 101  * security reasons.
 102  *
 103  * Also note that we take the address to load from from the file itself.
 104  */
 105 SYSCALL_DEFINE1(uselib, const char __user *, library)
 106 {
 107         struct file *file;
 108         struct nameidata nd;
 109         char *tmp = getname(library);
 110         int error = PTR_ERR(tmp);
 111
 112         if (!IS_ERR(tmp)) {
 113                 error = path_lookup_open(AT_FDCWD, tmp,
 114                                          LOOKUP_FOLLOW, &nd,
 115                                          FMODE_READ|FMODE_EXEC);
 116                 putname(tmp);
 117         }
 118         if (error)
 119                 goto out;
 120
 121         error = -EINVAL;
 122         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 123                 goto exit;
 124
 125         error = -EACCES;
 126         if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 127                 goto exit;
 128
 129         error = inode_permission(nd.path.dentry->d_inode,
 130                                  MAY_READ | MAY_EXEC | MAY_OPEN);
 131         if (error)
 132                 goto exit;
 133         error = ima_path_check(&nd.path, MAY_READ | MAY_EXEC | MAY_OPEN);
 134         if (error)
 135                 goto exit;
 136
 137         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 138         error = PTR_ERR(file);
 139         if (IS_ERR(file))
 140                 goto out;
 141
 142         fsnotify_open(file->f_path.dentry);
 143
 144         error = -ENOEXEC;
 145         if(file->f_op) {
 146                 struct linux_binfmt * fmt;
 147
 148                 read_lock(&binfmt_lock);
 149                 list_for_each_entry(fmt, &formats, lh) {
 150                         if (!fmt->load_shlib)
 151                                 continue;
 152                         if (!try_module_get(fmt->module))
 153                                 continue;
 154                         read_unlock(&binfmt_lock);
 155                         error = fmt->load_shlib(file);
 156                         read_lock(&binfmt_lock);
 157                         put_binfmt(fmt);
 158                         if (error != -ENOEXEC)
 159                                 break;
 160                 }
 161                 read_unlock(&binfmt_lock);
 162         }
 163         fput(file);
 164 out:
 165         return error;
 166 exit:
 167         release_open_intent(&nd);
 168         path_put(&nd.path);
 169         goto out;
 170 }
 171
 172 #ifdef CONFIG_MMU
 173
 174 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 175                 int write)
 176 {
 177         struct page *page;
 178         int ret;
 179
 180 #ifdef CONFIG_STACK_GROWSUP
 181         if (write) {
 182                 ret = expand_stack_downwards(bprm->vma, pos);
 183                 if (ret < 0)
 184                         return NULL;
 185         }
 186 #endif
 187         ret = get_user_pages(current, bprm->mm, pos,
 188                         1, write, 1, &page, NULL);
 189         if (ret <= 0)
 190                 return NULL;
 191
 192         if (write) {
 193                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 194                 struct rlimit *rlim;
 195
 196                 /*
 197                  * We've historically supported up to 32 pages (ARG_MAX)
 198                  * of argument strings even with small stacks
 199                  */
 200                 if (size <= ARG_MAX)
 201                         return page;
 202
 203                 /*
 204                  * Limit to 1/4-th the stack size for the argv+env strings.
 205                  * This ensures that:
 206                  *  - the remaining binfmt code will not run out of stack space,
 207                  *  - the program will have a reasonable amount of stack left
 208                  *    to work from.
 209                  */
 210                 rlim = current->signal->rlim;
 211                 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
 212                         put_page(page);
 213                         return NULL;
 214                 }
 215         }
 216
 217         return page;
 218 }
 219
 220 static void put_arg_page(struct page *page)
 221 {
 222         put_page(page);
 223 }
 224
 225 static void free_arg_page(struct linux_binprm *bprm, int i)
 226 {
 227 }
 228
 229 static void free_arg_pages(struct linux_binprm *bprm)
 230 {
 231 }
 232
 233 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 234                 struct page *page)
 235 {
 236         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 237 }
 238
 239 static int __bprm_mm_init(struct linux_binprm *bprm)
 240 {
 241         int err;
 242         struct vm_area_struct *vma = NULL;
 243         struct mm_struct *mm = bprm->mm;
 244
 245         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 246         if (!vma)
 247                 return -ENOMEM;
 248
 249         down_write(&mm->mmap_sem);
 250         vma->vm_mm = mm;
 251
 252         /*
 253          * Place the stack at the largest stack address the architecture
 254          * supports. Later, we'll move this to an appropriate place. We don't
 255          * use STACK_TOP because that can depend on attributes which aren't
 256          * configured yet.
 257          */
 258         vma->vm_end = STACK_TOP_MAX;
 259         vma->vm_start = vma->vm_end - PAGE_SIZE;
 260         vma->vm_flags = VM_STACK_FLAGS;
 261         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 262         err = insert_vm_struct(mm, vma);
 263         if (err)
 264                 goto err;
 265
 266         mm->stack_vm = mm->total_vm = 1;
 267         up_write(&mm->mmap_sem);
 268         bprm->p = vma->vm_end - sizeof(void *);
 269         return 0;
 270 err:
 271         up_write(&mm->mmap_sem);
 272         bprm->vma = NULL;
 273         kmem_cache_free(vm_area_cachep, vma);
 274         return err;
 275 }
 276
 277 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 278 {
 279         return len <= MAX_ARG_STRLEN;
 280 }
 281
 282 #else
 283
 284 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 285                 int write)
 286 {
 287         struct page *page;
 288
 289         page = bprm->page[pos / PAGE_SIZE];
 290         if (!page && write) {
 291                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 292                 if (!page)
 293                         return NULL;
 294                 bprm->page[pos / PAGE_SIZE] = page;
 295         }
 296
 297         return page;
 298 }
 299
 300 static void put_arg_page(struct page *page)
 301 {
 302 }
 303
 304 static void free_arg_page(struct linux_binprm *bprm, int i)
 305 {
 306         if (bprm->page[i]) {
 307                 __free_page(bprm->page[i]);
 308                 bprm->page[i] = NULL;
 309         }
 310 }
 311
 312 static void free_arg_pages(struct linux_binprm *bprm)
 313 {
 314         int i;
 315
 316         for (i = 0; i < MAX_ARG_PAGES; i++)
 317                 free_arg_page(bprm, i);
 318 }
 319
 320 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 321                 struct page *page)
 322 {
 323 }
 324
 325 static int __bprm_mm_init(struct linux_binprm *bprm)
 326 {
 327         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 328         return 0;
 329 }
 330
 331 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 332 {
 333         return len <= bprm->p;
 334 }
 335
 336 #endif /* CONFIG_MMU */
 337
 338 /*
 339  * Create a new mm_struct and populate it with a temporary stack
 340  * vm_area_struct.  We don't have enough context at this point to set the stack
 341  * flags, permissions, and offset, so we use temporary values.  We'll update
 342  * them later in setup_arg_pages().
 343  */
 344 int bprm_mm_init(struct linux_binprm *bprm)
 345 {
 346         int err;
 347         struct mm_struct *mm = NULL;
 348
 349         bprm->mm = mm = mm_alloc();
 350         err = -ENOMEM;
 351         if (!mm)
 352                 goto err;
 353
 354         err = init_new_context(current, mm);
 355         if (err)
 356                 goto err;
 357
 358         err = __bprm_mm_init(bprm);
 359         if (err)
 360                 goto err;
 361
 362         return 0;
 363
 364 err:
 365         if (mm) {
 366                 bprm->mm = NULL;
 367                 mmdrop(mm);
 368         }
 369
 370         return err;
 371 }
 372
 373 /*
 374  * count() counts the number of strings in array ARGV.
 375  */
 376 static int count(char __user * __user * argv, int max)
 377 {
 378         int i = 0;
 379
 380         if (argv != NULL) {
 381                 for (;;) {
 382                         char __user * p;
 383
 384                         if (get_user(p, argv))
 385                                 return -EFAULT;
 386                         if (!p)
 387                                 break;
 388                         argv++;
 389                         if (i++ >= max)
 390                                 return -E2BIG;
 391                         cond_resched();
 392                 }
 393         }
 394         return i;
 395 }
 396
 397 /*
 398  * 'copy_strings()' copies argument/environment strings from the old
 399  * processes's memory to the new process's stack.  The call to get_user_pages()
 400  * ensures the destination page is created and not swapped out.
 401  */
 402 static int copy_strings(int argc, char __user * __user * argv,
 403                         struct linux_binprm *bprm)
 404 {
 405         struct page *kmapped_page = NULL;
 406         char *kaddr = NULL;
 407         unsigned long kpos = 0;
 408         int ret;
 409
 410         while (argc-- > 0) {
 411                 char __user *str;
 412                 int len;
 413                 unsigned long pos;
 414
 415                 if (get_user(str, argv+argc) ||
 416                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 417                         ret = -EFAULT;
 418                         goto out;
 419                 }
 420
 421                 if (!valid_arg_len(bprm, len)) {
 422                         ret = -E2BIG;
 423                         goto out;
 424                 }
 425
 426                 /* We're going to work our way backwords. */
 427                 pos = bprm->p;
 428                 str += len;
 429                 bprm->p -= len;
 430
 431                 while (len > 0) {
 432                         int offset, bytes_to_copy;
 433
 434                         offset = pos % PAGE_SIZE;
 435                         if (offset == 0)
 436                                 offset = PAGE_SIZE;
 437
 438                         bytes_to_copy = offset;
 439                         if (bytes_to_copy > len)
 440                                 bytes_to_copy = len;
 441
 442                         offset -= bytes_to_copy;
 443                         pos -= bytes_to_copy;
 444                         str -= bytes_to_copy;
 445                         len -= bytes_to_copy;
 446
 447                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 448                                 struct page *page;
 449
 450                                 page = get_arg_page(bprm, pos, 1);
 451                                 if (!page) {
 452                                         ret = -E2BIG;
 453                                         goto out;
 454                                 }
 455
 456                                 if (kmapped_page) {
 457                                         flush_kernel_dcache_page(kmapped_page);
 458                                         kunmap(kmapped_page);
 459                                         put_arg_page(kmapped_page);
 460                                 }
 461                                 kmapped_page = page;
 462                                 kaddr = kmap(kmapped_page);
 463                                 kpos = pos & PAGE_MASK;
 464                                 flush_arg_page(bprm, kpos, kmapped_page);
 465                         }
 466                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 467                                 ret = -EFAULT;
 468                                 goto out;
 469                         }
 470                 }
 471         }
 472         ret = 0;
 473 out:
 474         if (kmapped_page) {
 475                 flush_kernel_dcache_page(kmapped_page);
 476                 kunmap(kmapped_page);
 477                 put_arg_page(kmapped_page);
 478         }
 479         return ret;
 480 }
 481
 482 /*
 483  * Like copy_strings, but get argv and its values from kernel memory.
 484  */
 485 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 486 {
 487         int r;
 488         mm_segment_t oldfs = get_fs();
 489         set_fs(KERNEL_DS);
 490         r = copy_strings(argc, (char __user * __user *)argv, bprm);
 491         set_fs(oldfs);
 492         return r;
 493 }
 494 EXPORT_SYMBOL(copy_strings_kernel);
 495
 496 #ifdef CONFIG_MMU
 497
 498 /*
 499  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 500  * the binfmt code determines where the new stack should reside, we shift it to
 501  * its final location.  The process proceeds as follows:
 502  *
 503  * 1) Use shift to calculate the new vma endpoints.
 504  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 505  *    arguments passed to subsequent functions are consistent.
 506  * 3) Move vma's page tables to the new range.
 507  * 4) Free up any cleared pgd range.
 508  * 5) Shrink the vma to cover only the new range.
 509  */
 510 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 511 {
 512         struct mm_struct *mm = vma->vm_mm;
 513         unsigned long old_start = vma->vm_start;
 514         unsigned long old_end = vma->vm_end;
 515         unsigned long length = old_end - old_start;
 516         unsigned long new_start = old_start - shift;
 517         unsigned long new_end = old_end - shift;
 518         struct mmu_gather *tlb;
 519
 520         BUG_ON(new_start > new_end);
 521
 522         /*
 523          * ensure there are no vmas between where we want to go
 524          * and where we are
 525          */
 526         if (vma != find_vma(mm, new_start))
 527                 return -EFAULT;
 528
 529         /*
 530          * cover the whole range: [new_start, old_end)
 531          */
 532         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 533
 534         /*
 535          * move the page tables downwards, on failure we rely on
 536          * process cleanup to remove whatever mess we made.
 537          */
 538         if (length != move_page_tables(vma, old_start,
 539                                        vma, new_start, length))
 540                 return -ENOMEM;
 541
 542         lru_add_drain();
 543         tlb = tlb_gather_mmu(mm, 0);
 544         if (new_end > old_start) {
 545                 /*
 546                  * when the old and new regions overlap clear from new_end.
 547                  */
 548                 free_pgd_range(tlb, new_end, old_end, new_end,
 549                         vma->vm_next ? vma->vm_next->vm_start : 0);
 550         } else {
 551                 /*
 552                  * otherwise, clean from old_start; this is done to not touch
 553                  * the address space in [new_end, old_start) some architectures
 554                  * have constraints on va-space that make this illegal (IA64) -
 555                  * for the others its just a little faster.
 556                  */
 557                 free_pgd_range(tlb, old_start, old_end, new_end,
 558                         vma->vm_next ? vma->vm_next->vm_start : 0);
 559         }
 560         tlb_finish_mmu(tlb, new_end, old_end);
 561
 562         /*
 563          * shrink the vma to just the new range.
 564          */
 565         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 566
 567         return 0;
 568 }
 569
 570 #define EXTRA_STACK_VM_PAGES    20      /* random */
 571
 572 /*
 573  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 574  * the stack is optionally relocated, and some extra space is added.
 575  */
 576 int setup_arg_pages(struct linux_binprm *bprm,
 577                     unsigned long stack_top,
 578                     int executable_stack)
 579 {
 580         unsigned long ret;
 581         unsigned long stack_shift;
 582         struct mm_struct *mm = current->mm;
 583         struct vm_area_struct *vma = bprm->vma;
 584         struct vm_area_struct *prev = NULL;
 585         unsigned long vm_flags;
 586         unsigned long stack_base;
 587
 588 #ifdef CONFIG_STACK_GROWSUP
 589         /* Limit stack size to 1GB */
 590         stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
 591         if (stack_base > (1 << 30))
 592                 stack_base = 1 << 30;
 593
 594         /* Make sure we didn't let the argument array grow too large. */
 595         if (vma->vm_end - vma->vm_start > stack_base)
 596                 return -ENOMEM;
 597
 598         stack_base = PAGE_ALIGN(stack_top - stack_base);
 599
 600         stack_shift = vma->vm_start - stack_base;
 601         mm->arg_start = bprm->p - stack_shift;
 602         bprm->p = vma->vm_end - stack_shift;
 603 #else
 604         stack_top = arch_align_stack(stack_top);
 605         stack_top = PAGE_ALIGN(stack_top);
 606         stack_shift = vma->vm_end - stack_top;
 607
 608         bprm->p -= stack_shift;
 609         mm->arg_start = bprm->p;
 610 #endif
 611
 612         if (bprm->loader)
 613                 bprm->loader -= stack_shift;
 614         bprm->exec -= stack_shift;
 615
 616         down_write(&mm->mmap_sem);
 617         vm_flags = VM_STACK_FLAGS;
 618
 619         /*
 620          * Adjust stack execute permissions; explicitly enable for
 621          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 622          * (arch default) otherwise.
 623          */
 624         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 625                 vm_flags |= VM_EXEC;
 626         else if (executable_stack == EXSTACK_DISABLE_X)
 627                 vm_flags &= ~VM_EXEC;
 628         vm_flags |= mm->def_flags;
 629
 630         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 631                         vm_flags);
 632         if (ret)
 633                 goto out_unlock;
 634         BUG_ON(prev != vma);
 635
 636         /* Move stack pages down in memory. */
 637         if (stack_shift) {
 638                 ret = shift_arg_pages(vma, stack_shift);
 639                 if (ret) {
 640                         up_write(&mm->mmap_sem);
 641                         return ret;
 642                 }
 643         }
 644
 645 #ifdef CONFIG_STACK_GROWSUP
 646         stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 647 #else
 648         stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 649 #endif
 650         ret = expand_stack(vma, stack_base);
 651         if (ret)
 652                 ret = -EFAULT;
 653
 654 out_unlock:
 655         up_write(&mm->mmap_sem);
 656         return 0;
 657 }
 658 EXPORT_SYMBOL(setup_arg_pages);
 659
 660 #endif /* CONFIG_MMU */
 661
 662 struct file *open_exec(const char *name)
 663 {
 664         struct nameidata nd;
 665         struct file *file;
 666         int err;
 667
 668         err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd,
 669                                 FMODE_READ|FMODE_EXEC);
 670         if (err)
 671                 goto out;
 672
 673         err = -EACCES;
 674         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 675                 goto out_path_put;
 676
 677         if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 678                 goto out_path_put;
 679
 680         err = inode_permission(nd.path.dentry->d_inode, MAY_EXEC | MAY_OPEN);
 681         if (err)
 682                 goto out_path_put;
 683         err = ima_path_check(&nd.path, MAY_EXEC | MAY_OPEN);
 684         if (err)
 685                 goto out_path_put;
 686
 687         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 688         if (IS_ERR(file))
 689                 return file;
 690
 691         fsnotify_open(file->f_path.dentry);
 692
 693         err = deny_write_access(file);
 694         if (err) {
 695                 fput(file);
 696                 goto out;
 697         }
 698
 699         return file;
 700
 701  out_path_put:
 702         release_open_intent(&nd);
 703         path_put(&nd.path);
 704  out:
 705         return ERR_PTR(err);
 706 }
 707 EXPORT_SYMBOL(open_exec);
 708
 709 int kernel_read(struct file *file, unsigned long offset,
 710         char *addr, unsigned long count)
 711 {
 712         mm_segment_t old_fs;
 713         loff_t pos = offset;
 714         int result;
 715
 716         old_fs = get_fs();
 717         set_fs(get_ds());
 718         /* The cast to a user pointer is valid due to the set_fs() */
 719         result = vfs_read(file, (void __user *)addr, count, &pos);
 720         set_fs(old_fs);
 721         return result;
 722 }
 723
 724 EXPORT_SYMBOL(kernel_read);
 725
 726 static int exec_mmap(struct mm_struct *mm)
 727 {
 728         struct task_struct *tsk;
 729         struct mm_struct * old_mm, *active_mm;
 730
 731         /* Notify parent that we're no longer interested in the old VM */
 732         tsk = current;
 733         old_mm = current->mm;
 734         mm_release(tsk, old_mm);
 735
 736         if (old_mm) {
 737                 /*
 738                  * Make sure that if there is a core dump in progress
 739                  * for the old mm, we get out and die instead of going
 740                  * through with the exec.  We must hold mmap_sem around
 741                  * checking core_state and changing tsk->mm.
 742                  */
 743                 down_read(&old_mm->mmap_sem);
 744                 if (unlikely(old_mm->core_state)) {
 745                         up_read(&old_mm->mmap_sem);
 746                         return -EINTR;
 747                 }
 748         }
 749         task_lock(tsk);
 750         active_mm = tsk->active_mm;
 751         tsk->mm = mm;
 752         tsk->active_mm = mm;
 753         activate_mm(active_mm, mm);
 754         task_unlock(tsk);
 755         arch_pick_mmap_layout(mm);
 756         if (old_mm) {
 757                 up_read(&old_mm->mmap_sem);
 758                 BUG_ON(active_mm != old_mm);
 759                 mm_update_next_owner(old_mm);
 760                 mmput(old_mm);
 761                 return 0;
 762         }
 763         mmdrop(active_mm);
 764         return 0;
 765 }
 766
 767 /*
 768  * This function makes sure the current process has its own signal table,
 769  * so that flush_signal_handlers can later reset the handlers without
 770  * disturbing other processes.  (Other processes might share the signal
 771  * table via the CLONE_SIGHAND option to clone().)
 772  */
 773 static int de_thread(struct task_struct *tsk)
 774 {
 775         struct signal_struct *sig = tsk->signal;
 776         struct sighand_struct *oldsighand = tsk->sighand;
 777         spinlock_t *lock = &oldsighand->siglock;
 778         int count;
 779
 780         if (thread_group_empty(tsk))
 781                 goto no_thread_group;
 782
 783         /*
 784          * Kill all other threads in the thread group.
 785          */
 786         spin_lock_irq(lock);
 787         if (signal_group_exit(sig)) {
 788                 /*
 789                  * Another group action in progress, just
 790                  * return so that the signal is processed.
 791                  */
 792                 spin_unlock_irq(lock);
 793                 return -EAGAIN;
 794         }
 795         sig->group_exit_task = tsk;
 796         zap_other_threads(tsk);
 797
 798         /* Account for the thread group leader hanging around: */
 799         count = thread_group_leader(tsk) ? 1 : 2;
 800         sig->notify_count = count;
 801         while (atomic_read(&sig->count) > count) {
 802                 __set_current_state(TASK_UNINTERRUPTIBLE);
 803                 spin_unlock_irq(lock);
 804                 schedule();
 805                 spin_lock_irq(lock);
 806         }
 807         spin_unlock_irq(lock);
 808
 809         /*
 810          * At this point all other threads have exited, all we have to
 811          * do is to wait for the thread group leader to become inactive,
 812          * and to assume its PID:
 813          */
 814         if (!thread_group_leader(tsk)) {
 815                 struct task_struct *leader = tsk->group_leader;
 816
 817                 sig->notify_count = -1; /* for exit_notify() */
 818                 for (;;) {
 819                         write_lock_irq(&tasklist_lock);
 820                         if (likely(leader->exit_state))
 821                                 break;
 822                         __set_current_state(TASK_UNINTERRUPTIBLE);
 823                         write_unlock_irq(&tasklist_lock);
 824                         schedule();
 825                 }
 826
 827                 /*
 828                  * The only record we have of the real-time age of a
 829                  * process, regardless of execs it's done, is start_time.
 830                  * All the past CPU time is accumulated in signal_struct
 831                  * from sister threads now dead.  But in this non-leader
 832                  * exec, nothing survives from the original leader thread,
 833                  * whose birth marks the true age of this process now.
 834                  * When we take on its identity by switching to its PID, we
 835                  * also take its birthdate (always earlier than our own).
 836                  */
 837                 tsk->start_time = leader->start_time;
 838
 839                 BUG_ON(!same_thread_group(leader, tsk));
 840                 BUG_ON(has_group_leader_pid(tsk));
 841                 /*
 842                  * An exec() starts a new thread group with the
 843                  * TGID of the previous thread group. Rehash the
 844                  * two threads with a switched PID, and release
 845                  * the former thread group leader:
 846                  */
 847
 848                 /* Become a process group leader with the old leader's pid.
 849                  * The old leader becomes a thread of the this thread group.
 850                  * Note: The old leader also uses this pid until release_task
 851                  *       is called.  Odd but simple and correct.
 852                  */
 853                 detach_pid(tsk, PIDTYPE_PID);
 854                 tsk->pid = leader->pid;
 855                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 856                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 857                 transfer_pid(leader, tsk, PIDTYPE_SID);
 858                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 859
 860                 tsk->group_leader = tsk;
 861                 leader->group_leader = tsk;
 862
 863                 tsk->exit_signal = SIGCHLD;
 864
 865                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 866                 leader->exit_state = EXIT_DEAD;
 867                 write_unlock_irq(&tasklist_lock);
 868
 869                 release_task(leader);
 870         }
 871
 872         sig->group_exit_task = NULL;
 873         sig->notify_count = 0;
 874
 875 no_thread_group:
 876         exit_itimers(sig);
 877         flush_itimer_signals();
 878
 879         if (atomic_read(&oldsighand->count) != 1) {
 880                 struct sighand_struct *newsighand;
 881                 /*
 882                  * This ->sighand is shared with the CLONE_SIGHAND
 883                  * but not CLONE_THREAD task, switch to the new one.
 884                  */
 885                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 886                 if (!newsighand)
 887                         return -ENOMEM;
 888
 889                 atomic_set(&newsighand->count, 1);
 890                 memcpy(newsighand->action, oldsighand->action,
 891                        sizeof(newsighand->action));
 892
 893                 write_lock_irq(&tasklist_lock);
 894                 spin_lock(&oldsighand->siglock);
 895                 rcu_assign_pointer(tsk->sighand, newsighand);
 896                 spin_unlock(&oldsighand->siglock);
 897                 write_unlock_irq(&tasklist_lock);
 898
 899                 __cleanup_sighand(oldsighand);
 900         }
 901
 902         BUG_ON(!thread_group_leader(tsk));
 903         return 0;
 904 }
 905
 906 /*
 907  * These functions flushes out all traces of the currently running executable
 908  * so that a new one can be started
 909  */
 910 static void flush_old_files(struct files_struct * files)
 911 {
 912         long j = -1;
 913         struct fdtable *fdt;
 914
 915         spin_lock(&files->file_lock);
 916         for (;;) {
 917                 unsigned long set, i;
 918
 919                 j++;
 920                 i = j * __NFDBITS;
 921                 fdt = files_fdtable(files);
 922                 if (i >= fdt->max_fds)
 923                         break;
 924                 set = fdt->close_on_exec->fds_bits[j];
 925                 if (!set)
 926                         continue;
 927                 fdt->close_on_exec->fds_bits[j] = 0;
 928                 spin_unlock(&files->file_lock);
 929                 for ( ; set ; i++,set >>= 1) {
 930                         if (set & 1) {
 931                                 sys_close(i);
 932                         }
 933                 }
 934                 spin_lock(&files->file_lock);
 935
 936         }
 937         spin_unlock(&files->file_lock);
 938 }
 939
 940 char *get_task_comm(char *buf, struct task_struct *tsk)
 941 {
 942         /* buf must be at least sizeof(tsk->comm) in size */
 943         task_lock(tsk);
 944         strncpy(buf, tsk->comm, sizeof(tsk->comm));
 945         task_unlock(tsk);
 946         return buf;
 947 }
 948
 949 void set_task_comm(struct task_struct *tsk, char *buf)
 950 {
 951         task_lock(tsk);
 952         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 953         task_unlock(tsk);
 954 }
 955
 956 int flush_old_exec(struct linux_binprm * bprm)
 957 {
 958         char * name;
 959         int i, ch, retval;
 960         char tcomm[sizeof(current->comm)];
 961
 962         /*
 963          * Make sure we have a private signal table and that
 964          * we are unassociated from the previous thread group.
 965          */
 966         retval = de_thread(current);
 967         if (retval)
 968                 goto out;
 969
 970         set_mm_exe_file(bprm->mm, bprm->file);
 971
 972         /*
 973          * Release all of the old mmap stuff
 974          */
 975         retval = exec_mmap(bprm->mm);
 976         if (retval)
 977                 goto out;
 978
 979         bprm->mm = NULL;                /* We're using it now */
 980
 981         /* This is the point of no return */
 982         current->sas_ss_sp = current->sas_ss_size = 0;
 983
 984         if (current_euid() == current_uid() && current_egid() == current_gid())
 985                 set_dumpable(current->mm, 1);
 986         else
 987                 set_dumpable(current->mm, suid_dumpable);
 988
 989         name = bprm->filename;
 990
 991         /* Copies the binary name from after last slash */
 992         for (i=0; (ch = *(name++)) != '\0';) {
 993                 if (ch == '/')
 994                         i = 0; /* overwrite what we wrote */
 995                 else
 996                         if (i < (sizeof(tcomm) - 1))
 997                                 tcomm[i++] = ch;
 998         }
 999         tcomm[i] = '\0';
1000         set_task_comm(current, tcomm);
1001
1002         current->flags &= ~PF_RANDOMIZE;
1003         flush_thread();
1004
1005         /* Set the new mm task size. We have to do that late because it may
1006          * depend on TIF_32BIT which is only updated in flush_thread() on
1007          * some architectures like powerpc
1008          */
1009         current->mm->task_size = TASK_SIZE;
1010
1011         /* install the new credentials */
1012         if (bprm->cred->uid != current_euid() ||
1013             bprm->cred->gid != current_egid()) {
1014                 current->pdeath_signal = 0;
1015         } else if (file_permission(bprm->file, MAY_READ) ||
1016                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1017                 set_dumpable(current->mm, suid_dumpable);
1018         }
1019
1020         current->personality &= ~bprm->per_clear;
1021
1022         /* An exec changes our domain. We are no longer part of the thread
1023            group */
1024
1025         current->self_exec_id++;
1026
1027         flush_signal_handlers(current, 0);
1028         flush_old_files(current->files);
1029
1030         return 0;
1031
1032 out:
1033         return retval;
1034 }
1035
1036 EXPORT_SYMBOL(flush_old_exec);
1037
1038 /*
1039  * install the new credentials for this executable
1040  */
1041 void install_exec_creds(struct linux_binprm *bprm)
1042 {
1043         security_bprm_committing_creds(bprm);
1044
1045         commit_creds(bprm->cred);
1046         bprm->cred = NULL;
1047
1048         /* cred_exec_mutex must be held at least to this point to prevent
1049          * ptrace_attach() from altering our determination of the task's
1050          * credentials; any time after this it may be unlocked */
1051
1052         security_bprm_committed_creds(bprm);
1053 }
1054 EXPORT_SYMBOL(install_exec_creds);
1055
1056 /*
1057  * determine how safe it is to execute the proposed program
1058  * - the caller must hold current->cred_exec_mutex to protect against
1059  *   PTRACE_ATTACH
1060  */
1061 int check_unsafe_exec(struct linux_binprm *bprm)
1062 {
1063         struct task_struct *p = current, *t;
1064         unsigned n_fs;
1065         int res = 0;
1066
1067         bprm->unsafe = tracehook_unsafe_exec(p);
1068
1069         n_fs = 1;
1070         write_lock(&p->fs->lock);
1071         rcu_read_lock();
1072         for (t = next_thread(p); t != p; t = next_thread(t)) {
1073                 if (t->fs == p->fs)
1074                         n_fs++;
1075         }
1076         rcu_read_unlock();
1077
1078         if (p->fs->users > n_fs) {
1079                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1080         } else {
1081                 res = -EAGAIN;
1082                 if (!p->fs->in_exec) {
1083                         p->fs->in_exec = 1;
1084                         res = 1;
1085                 }
1086         }
1087         write_unlock(&p->fs->lock);
1088
1089         return res;
1090 }
1091
1092 /*
1093  * Fill the binprm structure from the inode.
1094  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1095  *
1096  * This may be called multiple times for binary chains (scripts for example).
1097  */
1098 int prepare_binprm(struct linux_binprm *bprm)
1099 {
1100         umode_t mode;
1101         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1102         int retval;
1103
1104         mode = inode->i_mode;
1105         if (bprm->file->f_op == NULL)
1106                 return -EACCES;
1107
1108         /* clear any previous set[ug]id data from a previous binary */
1109         bprm->cred->euid = current_euid();
1110         bprm->cred->egid = current_egid();
1111
1112         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1113                 /* Set-uid? */
1114                 if (mode & S_ISUID) {
1115                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1116                         bprm->cred->euid = inode->i_uid;
1117                 }
1118
1119                 /* Set-gid? */
1120                 /*
1121                  * If setgid is set but no group execute bit then this
1122                  * is a candidate for mandatory locking, not a setgid
1123                  * executable.
1124                  */
1125                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1126                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1127                         bprm->cred->egid = inode->i_gid;
1128                 }
1129         }
1130
1131         /* fill in binprm security blob */
1132         retval = security_bprm_set_creds(bprm);
1133         if (retval)
1134                 return retval;
1135         bprm->cred_prepared = 1;
1136
1137         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1138         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1139 }
1140
1141 EXPORT_SYMBOL(prepare_binprm);
1142
1143 /*
1144  * Arguments are '\0' separated strings found at the location bprm->p
1145  * points to; chop off the first by relocating brpm->p to right after
1146  * the first '\0' encountered.
1147  */
1148 int remove_arg_zero(struct linux_binprm *bprm)
1149 {
1150         int ret = 0;
1151         unsigned long offset;
1152         char *kaddr;
1153         struct page *page;
1154
1155         if (!bprm->argc)
1156                 return 0;
1157
1158         do {
1159                 offset = bprm->p & ~PAGE_MASK;
1160                 page = get_arg_page(bprm, bprm->p, 0);
1161                 if (!page) {
1162                         ret = -EFAULT;
1163                         goto out;
1164                 }
1165                 kaddr = kmap_atomic(page, KM_USER0);
1166
1167                 for (; offset < PAGE_SIZE && kaddr[offset];
1168                                 offset++, bprm->p++)
1169                         ;
1170
1171                 kunmap_atomic(kaddr, KM_USER0);
1172                 put_arg_page(page);
1173
1174                 if (offset == PAGE_SIZE)
1175                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1176         } while (offset == PAGE_SIZE);
1177
1178         bprm->p++;
1179         bprm->argc--;
1180         ret = 0;
1181
1182 out:
1183         return ret;
1184 }
1185 EXPORT_SYMBOL(remove_arg_zero);
1186
1187 /*
1188  * cycle the list of binary formats handler, until one recognizes the image
1189  */
1190 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1191 {
1192         unsigned int depth = bprm->recursion_depth;
1193         int try,retval;
1194         struct linux_binfmt *fmt;
1195
1196         retval = security_bprm_check(bprm);
1197         if (retval)
1198                 return retval;
1199         retval = ima_bprm_check(bprm);
1200         if (retval)
1201                 return retval;
1202
1203         /* kernel module loader fixup */
1204         /* so we don't try to load run modprobe in kernel space. */
1205         set_fs(USER_DS);
1206
1207         retval = audit_bprm(bprm);
1208         if (retval)
1209                 return retval;
1210
1211         retval = -ENOENT;
1212         for (try=0; try<2; try++) {
1213                 read_lock(&binfmt_lock);
1214                 list_for_each_entry(fmt, &formats, lh) {
1215                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1216                         if (!fn)
1217                                 continue;
1218                         if (!try_module_get(fmt->module))
1219                                 continue;
1220                         read_unlock(&binfmt_lock);
1221                         retval = fn(bprm, regs);
1222                         /*
1223                          * Restore the depth counter to its starting value
1224                          * in this call, so we don't have to rely on every
1225                          * load_binary function to restore it on return.
1226                          */
1227                         bprm->recursion_depth = depth;
1228                         if (retval >= 0) {
1229                                 if (depth == 0)
1230                                         tracehook_report_exec(fmt, bprm, regs);
1231                                 put_binfmt(fmt);
1232                                 allow_write_access(bprm->file);
1233                                 if (bprm->file)
1234                                         fput(bprm->file);
1235                                 bprm->file = NULL;
1236                                 current->did_exec = 1;
1237                                 proc_exec_connector(current);
1238                                 return retval;
1239                         }
1240                         read_lock(&binfmt_lock);
1241                         put_binfmt(fmt);
1242                         if (retval != -ENOEXEC || bprm->mm == NULL)
1243                                 break;
1244                         if (!bprm->file) {
1245                                 read_unlock(&binfmt_lock);
1246                                 return retval;
1247                         }
1248                 }
1249                 read_unlock(&binfmt_lock);
1250                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1251                         break;
1252 #ifdef CONFIG_MODULES
1253                 } else {
1254 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1255                         if (printable(bprm->buf[0]) &&
1256                             printable(bprm->buf[1]) &&
1257                             printable(bprm->buf[2]) &&
1258                             printable(bprm->buf[3]))
1259                                 break; /* -ENOEXEC */
1260                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1261 #endif
1262                 }
1263         }
1264         return retval;
1265 }
1266
1267 EXPORT_SYMBOL(search_binary_handler);
1268
1269 void free_bprm(struct linux_binprm *bprm)
1270 {
1271         free_arg_pages(bprm);
1272         if (bprm->cred)
1273                 abort_creds(bprm->cred);
1274         kfree(bprm);
1275 }
1276
1277 /*
1278  * sys_execve() executes a new program.
1279  */
1280 int do_execve(char * filename,
1281         char __user *__user *argv,
1282         char __user *__user *envp,
1283         struct pt_regs * regs)
1284 {
1285         struct linux_binprm *bprm;
1286         struct file *file;
1287         struct files_struct *displaced;
1288         bool clear_in_exec;
1289         int retval;
1290
1291         retval = unshare_files(&displaced);
1292         if (retval)
1293                 goto out_ret;
1294
1295         retval = -ENOMEM;
1296         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1297         if (!bprm)
1298                 goto out_files;
1299
1300         retval = mutex_lock_interruptible(&current->cred_exec_mutex);
1301         if (retval < 0)
1302                 goto out_free;
1303         current->in_execve = 1;
1304
1305         retval = -ENOMEM;
1306         bprm->cred = prepare_exec_creds();
1307         if (!bprm->cred)
1308                 goto out_unlock;
1309
1310         retval = check_unsafe_exec(bprm);
1311         if (retval < 0)
1312                 goto out_unlock;
1313         clear_in_exec = retval;
1314
1315         file = open_exec(filename);
1316         retval = PTR_ERR(file);
1317         if (IS_ERR(file))
1318                 goto out_unmark;
1319
1320         sched_exec();
1321
1322         bprm->file = file;
1323         bprm->filename = filename;
1324         bprm->interp = filename;
1325
1326         retval = bprm_mm_init(bprm);
1327         if (retval)
1328                 goto out_file;
1329
1330         bprm->argc = count(argv, MAX_ARG_STRINGS);
1331         if ((retval = bprm->argc) < 0)
1332                 goto out;
1333
1334         bprm->envc = count(envp, MAX_ARG_STRINGS);
1335         if ((retval = bprm->envc) < 0)
1336                 goto out;
1337
1338         retval = prepare_binprm(bprm);
1339         if (retval < 0)
1340                 goto out;
1341
1342         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1343         if (retval < 0)
1344                 goto out;
1345
1346         bprm->exec = bprm->p;
1347         retval = copy_strings(bprm->envc, envp, bprm);
1348         if (retval < 0)
1349                 goto out;
1350
1351         retval = copy_strings(bprm->argc, argv, bprm);
1352         if (retval < 0)
1353                 goto out;
1354
1355         current->flags &= ~PF_KTHREAD;
1356         retval = search_binary_handler(bprm,regs);
1357         if (retval < 0)
1358                 goto out;
1359
1360         /* execve succeeded */
1361         current->fs->in_exec = 0;
1362         current->in_execve = 0;
1363         mutex_unlock(&current->cred_exec_mutex);
1364         acct_update_integrals(current);
1365         free_bprm(bprm);
1366         if (displaced)
1367                 put_files_struct(displaced);
1368         return retval;
1369
1370 out:
1371         if (bprm->mm)
1372                 mmput (bprm->mm);
1373
1374 out_file:
1375         if (bprm->file) {
1376                 allow_write_access(bprm->file);
1377                 fput(bprm->file);
1378         }
1379
1380 out_unmark:
1381         if (clear_in_exec)
1382                 current->fs->in_exec = 0;
1383
1384 out_unlock:
1385         current->in_execve = 0;
1386         mutex_unlock(&current->cred_exec_mutex);
1387
1388 out_free:
1389         free_bprm(bprm);
1390
1391 out_files:
1392         if (displaced)
1393                 reset_files_struct(displaced);
1394 out_ret:
1395         return retval;
1396 }
1397
1398 int set_binfmt(struct linux_binfmt *new)
1399 {
1400         struct linux_binfmt *old = current->binfmt;
1401
1402         if (new) {
1403                 if (!try_module_get(new->module))
1404                         return -1;
1405         }
1406         current->binfmt = new;
1407         if (old)
1408                 module_put(old->module);
1409         return 0;
1410 }
1411
1412 EXPORT_SYMBOL(set_binfmt);
1413
1414 /* format_corename will inspect the pattern parameter, and output a
1415  * name into corename, which must have space for at least
1416  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1417  */
1418 static int format_corename(char *corename, long signr)
1419 {
1420         const struct cred *cred = current_cred();
1421         const char *pat_ptr = core_pattern;
1422         int ispipe = (*pat_ptr == '|');
1423         char *out_ptr = corename;
1424         char *const out_end = corename + CORENAME_MAX_SIZE;
1425         int rc;
1426         int pid_in_pattern = 0;
1427
1428         /* Repeat as long as we have more pattern to process and more output
1429            space */
1430         while (*pat_ptr) {
1431                 if (*pat_ptr != '%') {
1432                         if (out_ptr == out_end)
1433                                 goto out;
1434                         *out_ptr++ = *pat_ptr++;
1435                 } else {
1436                         switch (*++pat_ptr) {
1437                         case 0:
1438                                 goto out;
1439                         /* Double percent, output one percent */
1440                         case '%':
1441                                 if (out_ptr == out_end)
1442                                         goto out;
1443                                 *out_ptr++ = '%';
1444                                 break;
1445                         /* pid */
1446                         case 'p':
1447                                 pid_in_pattern = 1;
1448                                 rc = snprintf(out_ptr, out_end - out_ptr,
1449                                               "%d", task_tgid_vnr(current));
1450                                 if (rc > out_end - out_ptr)
1451                                         goto out;
1452                                 out_ptr += rc;
1453                                 break;
1454                         /* uid */
1455                         case 'u':
1456                                 rc = snprintf(out_ptr, out_end - out_ptr,
1457                                               "%d", cred->uid);
1458                                 if (rc > out_end - out_ptr)
1459                                         goto out;
1460                                 out_ptr += rc;
1461                                 break;
1462                         /* gid */
1463                         case 'g':
1464                                 rc = snprintf(out_ptr, out_end - out_ptr,
1465                                               "%d", cred->gid);
1466                                 if (rc > out_end - out_ptr)
1467                                         goto out;
1468                                 out_ptr += rc;
1469                                 break;
1470                         /* signal that caused the coredump */
1471                         case 's':
1472                                 rc = snprintf(out_ptr, out_end - out_ptr,
1473                                               "%ld", signr);
1474                                 if (rc > out_end - out_ptr)
1475                                         goto out;
1476                                 out_ptr += rc;
1477                                 break;
1478                         /* UNIX time of coredump */
1479                         case 't': {
1480                                 struct timeval tv;
1481                                 do_gettimeofday(&tv);
1482                                 rc = snprintf(out_ptr, out_end - out_ptr,
1483                                               "%lu", tv.tv_sec);
1484                                 if (rc > out_end - out_ptr)
1485                                         goto out;
1486                                 out_ptr += rc;
1487                                 break;
1488                         }
1489                         /* hostname */
1490                         case 'h':
1491                                 down_read(&uts_sem);
1492                                 rc = snprintf(out_ptr, out_end - out_ptr,
1493                                               "%s", utsname()->nodename);
1494                                 up_read(&uts_sem);
1495                                 if (rc > out_end - out_ptr)
1496                                         goto out;
1497                                 out_ptr += rc;
1498                                 break;
1499                         /* executable */
1500                         case 'e':
1501                                 rc = snprintf(out_ptr, out_end - out_ptr,
1502                                               "%s", current->comm);
1503                                 if (rc > out_end - out_ptr)
1504                                         goto out;
1505                                 out_ptr += rc;
1506                                 break;
1507                         /* core limit size */
1508                         case 'c':
1509                                 rc = snprintf(out_ptr, out_end - out_ptr,
1510                                               "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1511                                 if (rc > out_end - out_ptr)
1512                                         goto out;
1513                                 out_ptr += rc;
1514                                 break;
1515                         default:
1516                                 break;
1517                         }
1518                         ++pat_ptr;
1519                 }
1520         }
1521         /* Backward compatibility with core_uses_pid:
1522          *
1523          * If core_pattern does not include a %p (as is the default)
1524          * and core_uses_pid is set, then .%pid will be appended to
1525          * the filename. Do not do this for piped commands. */
1526         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1527                 rc = snprintf(out_ptr, out_end - out_ptr,
1528                               ".%d", task_tgid_vnr(current));
1529                 if (rc > out_end - out_ptr)
1530                         goto out;
1531                 out_ptr += rc;
1532         }
1533 out:
1534         *out_ptr = 0;
1535         return ispipe;
1536 }
1537
1538 static int zap_process(struct task_struct *start)
1539 {
1540         struct task_struct *t;
1541         int nr = 0;
1542
1543         start->signal->flags = SIGNAL_GROUP_EXIT;
1544         start->signal->group_stop_count = 0;
1545
1546         t = start;
1547         do {
1548                 if (t != current && t->mm) {
1549                         sigaddset(&t->pending.signal, SIGKILL);
1550                         signal_wake_up(t, 1);
1551                         nr++;
1552                 }
1553         } while_each_thread(start, t);
1554
1555         return nr;
1556 }
1557
1558 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1559                                 struct core_state *core_state, int exit_code)
1560 {
1561         struct task_struct *g, *p;
1562         unsigned long flags;
1563         int nr = -EAGAIN;
1564
1565         spin_lock_irq(&tsk->sighand->siglock);
1566         if (!signal_group_exit(tsk->signal)) {
1567                 mm->core_state = core_state;
1568                 tsk->signal->group_exit_code = exit_code;
1569                 nr = zap_process(tsk);
1570         }
1571         spin_unlock_irq(&tsk->sighand->siglock);
1572         if (unlikely(nr < 0))
1573                 return nr;
1574
1575         if (atomic_read(&mm->mm_users) == nr + 1)
1576                 goto done;
1577         /*
1578          * We should find and kill all tasks which use this mm, and we should
1579          * count them correctly into ->nr_threads. We don't take tasklist
1580          * lock, but this is safe wrt:
1581          *
1582          * fork:
1583          *      None of sub-threads can fork after zap_process(leader). All
1584          *      processes which were created before this point should be
1585          *      visible to zap_threads() because copy_process() adds the new
1586          *      process to the tail of init_task.tasks list, and lock/unlock
1587          *      of ->siglock provides a memory barrier.
1588          *
1589          * do_exit:
1590          *      The caller holds mm->mmap_sem. This means that the task which
1591          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1592          *      its ->mm.
1593          *
1594          * de_thread:
1595          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1596          *      we must see either old or new leader, this does not matter.
1597          *      However, it can change p->sighand, so lock_task_sighand(p)
1598          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1599          *      it can't fail.
1600          *
1601          *      Note also that "g" can be the old leader with ->mm == NULL
1602          *      and already unhashed and thus removed from ->thread_group.
1603          *      This is OK, __unhash_process()->list_del_rcu() does not
1604          *      clear the ->next pointer, we will find the new leader via
1605          *      next_thread().
1606          */
1607         rcu_read_lock();
1608         for_each_process(g) {
1609                 if (g == tsk->group_leader)
1610                         continue;
1611                 if (g->flags & PF_KTHREAD)
1612                         continue;
1613                 p = g;
1614                 do {
1615                         if (p->mm) {
1616                                 if (unlikely(p->mm == mm)) {
1617                                         lock_task_sighand(p, &flags);
1618                                         nr += zap_process(p);
1619                                         unlock_task_sighand(p, &flags);
1620                                 }
1621                                 break;
1622                         }
1623                 } while_each_thread(g, p);
1624         }
1625         rcu_read_unlock();
1626 done:
1627         atomic_set(&core_state->nr_threads, nr);
1628         return nr;
1629 }
1630
1631 static int coredump_wait(int exit_code, struct core_state *core_state)
1632 {
1633         struct task_struct *tsk = current;
1634         struct mm_struct *mm = tsk->mm;
1635         struct completion *vfork_done;
1636         int core_waiters;
1637
1638         init_completion(&core_state->startup);
1639         core_state->dumper.task = tsk;
1640         core_state->dumper.next = NULL;
1641         core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1642         up_write(&mm->mmap_sem);
1643
1644         if (unlikely(core_waiters < 0))
1645                 goto fail;
1646
1647         /*
1648          * Make sure nobody is waiting for us to release the VM,
1649          * otherwise we can deadlock when we wait on each other
1650          */
1651         vfork_done = tsk->vfork_done;
1652         if (vfork_done) {
1653                 tsk->vfork_done = NULL;
1654                 complete(vfork_done);
1655         }
1656
1657         if (core_waiters)
1658                 wait_for_completion(&core_state->startup);
1659 fail:
1660         return core_waiters;
1661 }
1662
1663 static void coredump_finish(struct mm_struct *mm)
1664 {
1665         struct core_thread *curr, *next;
1666         struct task_struct *task;
1667
1668         next = mm->core_state->dumper.next;
1669         while ((curr = next) != NULL) {
1670                 next = curr->next;
1671                 task = curr->task;
1672                 /*
1673                  * see exit_mm(), curr->task must not see
1674                  * ->task == NULL before we read ->next.
1675                  */
1676                 smp_mb();
1677                 curr->task = NULL;
1678                 wake_up_process(task);
1679         }
1680
1681         mm->core_state = NULL;
1682 }
1683
1684 /*
1685  * set_dumpable converts traditional three-value dumpable to two flags and
1686  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1687  * these bits are not changed atomically.  So get_dumpable can observe the
1688  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1689  * return either old dumpable or new one by paying attention to the order of
1690  * modifying the bits.
1691  *
1692  * dumpable |   mm->flags (binary)
1693  * old  new | initial interim  final
1694  * ---------+-----------------------
1695  *  0    1  |   00      01      01
1696  *  0    2  |   00      10(*)   11
1697  *  1    0  |   01      00      00
1698  *  1    2  |   01      11      11
1699  *  2    0  |   11      10(*)   00
1700  *  2    1  |   11      11      01
1701  *
1702  * (*) get_dumpable regards interim value of 10 as 11.
1703  */
1704 void set_dumpable(struct mm_struct *mm, int value)
1705 {
1706         switch (value) {
1707         case 0:
1708                 clear_bit(MMF_DUMPABLE, &mm->flags);
1709                 smp_wmb();
1710                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1711                 break;
1712         case 1:
1713                 set_bit(MMF_DUMPABLE, &mm->flags);
1714                 smp_wmb();
1715                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1716                 break;
1717         case 2:
1718                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1719                 smp_wmb();
1720                 set_bit(MMF_DUMPABLE, &mm->flags);
1721                 break;
1722         }
1723 }
1724
1725 int get_dumpable(struct mm_struct *mm)
1726 {
1727         int ret;
1728
1729         ret = mm->flags & 0x3;
1730         return (ret >= 2) ? 2 : ret;
1731 }
1732
1733 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1734 {
1735         struct core_state core_state;
1736         char corename[CORENAME_MAX_SIZE + 1];
1737         struct mm_struct *mm = current->mm;
1738         struct linux_binfmt * binfmt;
1739         struct inode * inode;
1740         struct file * file;
1741         const struct cred *old_cred;
1742         struct cred *cred;
1743         int retval = 0;
1744         int flag = 0;
1745         int ispipe = 0;
1746         unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1747         char **helper_argv = NULL;
1748         int helper_argc = 0;
1749         char *delimit;
1750
1751         audit_core_dumps(signr);
1752
1753         binfmt = current->binfmt;
1754         if (!binfmt || !binfmt->core_dump)
1755                 goto fail;
1756
1757         cred = prepare_creds();
1758         if (!cred) {
1759                 retval = -ENOMEM;
1760                 goto fail;
1761         }
1762
1763         down_write(&mm->mmap_sem);
1764         /*
1765          * If another thread got here first, or we are not dumpable, bail out.
1766          */
1767         if (mm->core_state || !get_dumpable(mm)) {
1768                 up_write(&mm->mmap_sem);
1769                 put_cred(cred);
1770                 goto fail;
1771         }
1772
1773         /*
1774          *      We cannot trust fsuid as being the "true" uid of the
1775          *      process nor do we know its entire history. We only know it
1776          *      was tainted so we dump it as root in mode 2.
1777          */
1778         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1779                 flag = O_EXCL;          /* Stop rewrite attacks */
1780                 cred->fsuid = 0;        /* Dump root private */
1781         }
1782
1783         retval = coredump_wait(exit_code, &core_state);
1784         if (retval < 0) {
1785                 put_cred(cred);
1786                 goto fail;
1787         }
1788
1789         old_cred = override_creds(cred);
1790
1791         /*
1792          * Clear any false indication of pending signals that might
1793          * be seen by the filesystem code called to write the core file.
1794          */
1795         clear_thread_flag(TIF_SIGPENDING);
1796
1797         /*
1798          * lock_kernel() because format_corename() is controlled by sysctl, which
1799          * uses lock_kernel()
1800          */
1801         lock_kernel();
1802         ispipe = format_corename(corename, signr);
1803         unlock_kernel();
1804         /*
1805          * Don't bother to check the RLIMIT_CORE value if core_pattern points
1806          * to a pipe.  Since we're not writing directly to the filesystem
1807          * RLIMIT_CORE doesn't really apply, as no actual core file will be
1808          * created unless the pipe reader choses to write out the core file
1809          * at which point file size limits and permissions will be imposed
1810          * as it does with any other process
1811          */
1812         if ((!ispipe) && (core_limit < binfmt->min_coredump))
1813                 goto fail_unlock;
1814
1815         if (ispipe) {
1816                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1817                 if (!helper_argv) {
1818                         printk(KERN_WARNING "%s failed to allocate memory\n",
1819                                __func__);
1820                         goto fail_unlock;
1821                 }
1822                 /* Terminate the string before the first option */
1823                 delimit = strchr(corename, ' ');
1824                 if (delimit)
1825                         *delimit = '\0';
1826                 delimit = strrchr(helper_argv[0], '/');
1827                 if (delimit)
1828                         delimit++;
1829                 else
1830                         delimit = helper_argv[0];
1831                 if (!strcmp(delimit, current->comm)) {
1832                         printk(KERN_NOTICE "Recursive core dump detected, "
1833                                         "aborting\n");
1834                         goto fail_unlock;
1835                 }
1836
1837                 core_limit = RLIM_INFINITY;
1838
1839                 /* SIGPIPE can happen, but it's just never processed */
1840                 if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
1841                                 &file)) {
1842                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1843                                corename);
1844                         goto fail_unlock;
1845                 }
1846         } else
1847                 file = filp_open(corename,
1848                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1849                                  0600);
1850         if (IS_ERR(file))
1851                 goto fail_unlock;
1852         inode = file->f_path.dentry->d_inode;
1853         if (inode->i_nlink > 1)
1854                 goto close_fail;        /* multiple links - don't dump */
1855         if (!ispipe && d_unhashed(file->f_path.dentry))
1856                 goto close_fail;
1857
1858         /* AK: actually i see no reason to not allow this for named pipes etc.,
1859            but keep the previous behaviour for now. */
1860         if (!ispipe && !S_ISREG(inode->i_mode))
1861                 goto close_fail;
1862         /*
1863          * Dont allow local users get cute and trick others to coredump
1864          * into their pre-created files:
1865          */
1866         if (inode->i_uid != current_fsuid())
1867                 goto close_fail;
1868         if (!file->f_op)
1869                 goto close_fail;
1870         if (!file->f_op->write)
1871                 goto close_fail;
1872         if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1873                 goto close_fail;
1874
1875         retval = binfmt->core_dump(signr, regs, file, core_limit);
1876
1877         if (retval)
1878                 current->signal->group_exit_code |= 0x80;
1879 close_fail:
1880         filp_close(file, NULL);
1881 fail_unlock:
1882         if (helper_argv)
1883                 argv_free(helper_argv);
1884
1885         revert_creds(old_cred);
1886         put_cred(cred);
1887         coredump_finish(mm);
1888 fail:
1889         return;
1890 }