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