kernel/futex_compat.c

   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 #include <linux/ptrace.h>
  14 #include <linux/syscalls.h>
  15
  16 #include <asm/uaccess.h>
  17
  18
  19 /*
  20  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
  21  */
  22 static inline int
  23 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
  24                    compat_uptr_t __user *head, unsigned int *pi)
  25 {
  26         if (get_user(*uentry, head))
  27                 return -EFAULT;
  28
  29         *entry = compat_ptr((*uentry) & ~1);
  30         *pi = (unsigned int)(*uentry) & 1;
  31
  32         return 0;
  33 }
  34
  35 static void __user *futex_uaddr(struct robust_list __user *entry,
  36                                 compat_long_t futex_offset)
  37 {
  38         compat_uptr_t base = ptr_to_compat(entry);
  39         void __user *uaddr = compat_ptr(base + futex_offset);
  40
  41         return uaddr;
  42 }
  43
  44 /*
  45  * Walk curr->robust_list (very carefully, it's a userspace list!)
  46  * and mark any locks found there dead, and notify any waiters.
  47  *
  48  * We silently return on any sign of list-walking problem.
  49  */
  50 void compat_exit_robust_list(struct task_struct *curr)
  51 {
  52         struct compat_robust_list_head __user *head = curr->compat_robust_list;
  53         struct robust_list __user *entry, *next_entry, *pending;
  54         unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
  55         unsigned int uninitialized_var(next_pi);
  56         compat_uptr_t uentry, next_uentry, upending;
  57         compat_long_t futex_offset;
  58         int rc;
  59
  60         if (!futex_cmpxchg_enabled)
  61                 return;
  62
  63         /*
  64          * Fetch the list head (which was registered earlier, via
  65          * sys_set_robust_list()):
  66          */
  67         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  68                 return;
  69         /*
  70          * Fetch the relative futex offset:
  71          */
  72         if (get_user(futex_offset, &head->futex_offset))
  73                 return;
  74         /*
  75          * Fetch any possibly pending lock-add first, and handle it
  76          * if it exists:
  77          */
  78         if (fetch_robust_entry(&upending, &pending,
  79                                &head->list_op_pending, &pip))
  80                 return;
  81
  82         next_entry = NULL;      /* avoid warning with gcc */
  83         while (entry != (struct robust_list __user *) &head->list) {
  84                 /*
  85                  * Fetch the next entry in the list before calling
  86                  * handle_futex_death:
  87                  */
  88                 rc = fetch_robust_entry(&next_uentry, &next_entry,
  89                         (compat_uptr_t __user *)&entry->next, &next_pi);
  90                 /*
  91                  * A pending lock might already be on the list, so
  92                  * dont process it twice:
  93                  */
  94                 if (entry != pending) {
  95                         void __user *uaddr = futex_uaddr(entry, futex_offset);
  96
  97                         if (handle_futex_death(uaddr, curr, pi))
  98                                 return;
  99                 }
 100                 if (rc)
 101                         return;
 102                 uentry = next_uentry;
 103                 entry = next_entry;
 104                 pi = next_pi;
 105                 /*
 106                  * Avoid excessively long or circular lists:
 107                  */
 108                 if (!--limit)
 109                         break;
 110
 111                 cond_resched();
 112         }
 113         if (pending) {
 114                 void __user *uaddr = futex_uaddr(pending, futex_offset);
 115
 116                 handle_futex_death(uaddr, curr, pip);
 117         }
 118 }
 119
 120 COMPAT_SYSCALL_DEFINE2(set_robust_list,
 121                 struct compat_robust_list_head __user *, head,
 122                 compat_size_t, len)
 123 {
 124         if (!futex_cmpxchg_enabled)
 125                 return -ENOSYS;
 126
 127         if (unlikely(len != sizeof(*head)))
 128                 return -EINVAL;
 129
 130         current->compat_robust_list = head;
 131
 132         return 0;
 133 }
 134
 135 COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
 136                         compat_uptr_t __user *, head_ptr,
 137                         compat_size_t __user *, len_ptr)
 138 {
 139         struct compat_robust_list_head __user *head;
 140         unsigned long ret;
 141         struct task_struct *p;
 142
 143         if (!futex_cmpxchg_enabled)
 144                 return -ENOSYS;
 145
 146         rcu_read_lock();
 147
 148         ret = -ESRCH;
 149         if (!pid)
 150                 p = current;
 151         else {
 152                 p = find_task_by_vpid(pid);
 153                 if (!p)
 154                         goto err_unlock;
 155         }
 156
 157         ret = -EPERM;
 158         if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
 159                 goto err_unlock;
 160
 161         head = p->compat_robust_list;
 162         rcu_read_unlock();
 163
 164         if (put_user(sizeof(*head), len_ptr))
 165                 return -EFAULT;
 166         return put_user(ptr_to_compat(head), head_ptr);
 167
 168 err_unlock:
 169         rcu_read_unlock();
 170
 171         return ret;
 172 }
 173
 174 COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
 175                 struct compat_timespec __user *, utime, u32 __user *, uaddr2,
 176                 u32, val3)
 177 {
 178         struct timespec ts;
 179         ktime_t t, *tp = NULL;
 180         int val2 = 0;
 181         int cmd = op & FUTEX_CMD_MASK;
 182
 183         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
 184                       cmd == FUTEX_WAIT_BITSET ||
 185                       cmd == FUTEX_WAIT_REQUEUE_PI)) {
 186                 if (compat_get_timespec(&ts, utime))
 187                         return -EFAULT;
 188                 if (!timespec_valid(&ts))
 189                         return -EINVAL;
 190
 191                 t = timespec_to_ktime(ts);
 192                 if (cmd == FUTEX_WAIT)
 193                         t = ktime_add_safe(ktime_get(), t);
 194                 tp = &t;
 195         }
 196         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
 197             cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
 198                 val2 = (int) (unsigned long) utime;
 199
 200         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 201 }