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   1 /*
   2  * linux/kernel/futex_compat.c
   3  *
   4  * Futex compatibililty routines.
   5  *
   6  * Copyright 2006, Red Hat, Inc., Ingo Molnar
   7  */
   8
   9 #include <linux/linkage.h>
  10 #include <linux/compat.h>
  11 #include <linux/nsproxy.h>
  12 #include <linux/futex.h>
  13
  14 #include <asm/uaccess.h>
  15
  16
  17 /*
  18  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
  19  */
  20 static inline int
  21 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
  22                    compat_uptr_t __user *head, int *pi)
  23 {
  24         if (get_user(*uentry, head))
  25                 return -EFAULT;
  26
  27         *entry = compat_ptr((*uentry) & ~1);
  28         *pi = (unsigned int)(*uentry) & 1;
  29
  30         return 0;
  31 }
  32
  33 static void __user *futex_uaddr(struct robust_list __user *entry,
  34                                 compat_long_t futex_offset)
  35 {
  36         compat_uptr_t base = ptr_to_compat(entry);
  37         void __user *uaddr = compat_ptr(base + futex_offset);
  38
  39         return uaddr;
  40 }
  41
  42 /*
  43  * Walk curr->robust_list (very carefully, it's a userspace list!)
  44  * and mark any locks found there dead, and notify any waiters.
  45  *
  46  * We silently return on any sign of list-walking problem.
  47  */
  48 void compat_exit_robust_list(struct task_struct *curr)
  49 {
  50         struct compat_robust_list_head __user *head = curr->compat_robust_list;
  51         struct robust_list __user *entry, *next_entry, *pending;
  52         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
  53         compat_uptr_t uentry, next_uentry, upending;
  54         compat_long_t futex_offset;
  55         int rc;
  56
  57         if (!futex_cmpxchg_enabled)
  58                 return;
  59
  60         /*
  61          * Fetch the list head (which was registered earlier, via
  62          * sys_set_robust_list()):
  63          */
  64         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  65                 return;
  66         /*
  67          * Fetch the relative futex offset:
  68          */
  69         if (get_user(futex_offset, &head->futex_offset))
  70                 return;
  71         /*
  72          * Fetch any possibly pending lock-add first, and handle it
  73          * if it exists:
  74          */
  75         if (fetch_robust_entry(&upending, &pending,
  76                                &head->list_op_pending, &pip))
  77                 return;
  78
  79         next_entry = NULL;      /* avoid warning with gcc */
  80         while (entry != (struct robust_list __user *) &head->list) {
  81                 /*
  82                  * Fetch the next entry in the list before calling
  83                  * handle_futex_death:
  84                  */
  85                 rc = fetch_robust_entry(&next_uentry, &next_entry,
  86                         (compat_uptr_t __user *)&entry->next, &next_pi);
  87                 /*
  88                  * A pending lock might already be on the list, so
  89                  * dont process it twice:
  90                  */
  91                 if (entry != pending) {
  92                         void __user *uaddr = futex_uaddr(entry, futex_offset);
  93
  94                         if (handle_futex_death(uaddr, curr, pi))
  95                                 return;
  96                 }
  97                 if (rc)
  98                         return;
  99                 uentry = next_uentry;
 100                 entry = next_entry;
 101                 pi = next_pi;
 102                 /*
 103                  * Avoid excessively long or circular lists:
 104                  */
 105                 if (!--limit)
 106                         break;
 107
 108                 cond_resched();
 109         }
 110         if (pending) {
 111                 void __user *uaddr = futex_uaddr(pending, futex_offset);
 112
 113                 handle_futex_death(uaddr, curr, pip);
 114         }
 115 }
 116
 117 asmlinkage long
 118 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 119                            compat_size_t len)
 120 {
 121         if (!futex_cmpxchg_enabled)
 122                 return -ENOSYS;
 123
 124         if (unlikely(len != sizeof(*head)))
 125                 return -EINVAL;
 126
 127         current->compat_robust_list = head;
 128
 129         return 0;
 130 }
 131
 132 asmlinkage long
 133 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 134                            compat_size_t __user *len_ptr)
 135 {
 136         struct compat_robust_list_head __user *head;
 137         unsigned long ret;
 138         const struct cred *cred = current_cred(), *pcred;
 139
 140         if (!futex_cmpxchg_enabled)
 141                 return -ENOSYS;
 142
 143         if (!pid)
 144                 head = current->compat_robust_list;
 145         else {
 146                 struct task_struct *p;
 147
 148                 ret = -ESRCH;
 149                 read_lock(&tasklist_lock);
 150                 p = find_task_by_vpid(pid);
 151                 if (!p)
 152                         goto err_unlock;
 153                 ret = -EPERM;
 154                 pcred = __task_cred(p);
 155                 if (cred->euid != pcred->euid &&
 156                     cred->euid != pcred->uid &&
 157                     !capable(CAP_SYS_PTRACE))
 158                         goto err_unlock;
 159                 head = p->compat_robust_list;
 160                 read_unlock(&tasklist_lock);
 161         }
 162
 163         if (put_user(sizeof(*head), len_ptr))
 164                 return -EFAULT;
 165         return put_user(ptr_to_compat(head), head_ptr);
 166
 167 err_unlock:
 168         read_unlock(&tasklist_lock);
 169
 170         return ret;
 171 }
 172
 173 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 174                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 175                 u32 val3)
 176 {
 177         struct timespec ts;
 178         ktime_t t, *tp = NULL;
 179         int val2 = 0;
 180         int cmd = op & FUTEX_CMD_MASK;
 181
 182         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
 183                       cmd == FUTEX_WAIT_BITSET)) {
 184                 if (get_compat_timespec(&ts, utime))
 185                         return -EFAULT;
 186                 if (!timespec_valid(&ts))
 187                         return -EINVAL;
 188
 189                 t = timespec_to_ktime(ts);
 190                 if (cmd == FUTEX_WAIT)
 191                         t = ktime_add_safe(ktime_get(), t);
 192                 tp = &t;
 193         }
 194         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
 195                 val2 = (int) (unsigned long) utime;
 196
 197         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 198 }