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
  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 /*
  34  * Walk curr->robust_list (very carefully, it's a userspace list!)
  35  * and mark any locks found there dead, and notify any waiters.
  36  *
  37  * We silently return on any sign of list-walking problem.
  38  */
  39 void compat_exit_robust_list(struct task_struct *curr)
  40 {
  41         struct compat_robust_list_head __user *head = curr->compat_robust_list;
  42         struct robust_list __user *entry, *next_entry, *pending;
  43         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
  44         compat_uptr_t uentry, next_uentry, upending;
  45         compat_long_t futex_offset;
  46         int rc;
  47
  48         /*
  49          * Fetch the list head (which was registered earlier, via
  50          * sys_set_robust_list()):
  51          */
  52         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  53                 return;
  54         /*
  55          * Fetch the relative futex offset:
  56          */
  57         if (get_user(futex_offset, &head->futex_offset))
  58                 return;
  59         /*
  60          * Fetch any possibly pending lock-add first, and handle it
  61          * if it exists:
  62          */
  63         if (fetch_robust_entry(&upending, &pending,
  64                                &head->list_op_pending, &pip))
  65                 return;
  66
  67         next_entry = NULL;      /* avoid warning with gcc */
  68         while (entry != (struct robust_list __user *) &head->list) {
  69                 /*
  70                  * Fetch the next entry in the list before calling
  71                  * handle_futex_death:
  72                  */
  73                 rc = fetch_robust_entry(&next_uentry, &next_entry,
  74                         (compat_uptr_t __user *)&entry->next, &next_pi);
  75                 /*
  76                  * A pending lock might already be on the list, so
  77                  * dont process it twice:
  78                  */
  79                 if (entry != pending)
  80                         if (handle_futex_death((void __user *)entry + futex_offset,
  81                                                 curr, pi))
  82                                 return;
  83
  84                 if (rc)
  85                         return;
  86                 uentry = next_uentry;
  87                 entry = next_entry;
  88                 pi = next_pi;
  89                 /*
  90                  * Avoid excessively long or circular lists:
  91                  */
  92                 if (!--limit)
  93                         break;
  94
  95                 cond_resched();
  96         }
  97         if (pending)
  98                 handle_futex_death((void __user *)pending + futex_offset,
  99                                    curr, pip);
 100 }
 101
 102 asmlinkage long
 103 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 104                            compat_size_t len)
 105 {
 106         if (unlikely(len != sizeof(*head)))
 107                 return -EINVAL;
 108
 109         current->compat_robust_list = head;
 110
 111         return 0;
 112 }
 113
 114 asmlinkage long
 115 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 116                            compat_size_t __user *len_ptr)
 117 {
 118         struct compat_robust_list_head __user *head;
 119         unsigned long ret;
 120
 121         if (!pid)
 122                 head = current->compat_robust_list;
 123         else {
 124                 struct task_struct *p;
 125
 126                 ret = -ESRCH;
 127                 read_lock(&tasklist_lock);
 128                 p = find_task_by_vpid(pid);
 129                 if (!p)
 130                         goto err_unlock;
 131                 ret = -EPERM;
 132                 if ((current->euid != p->euid) && (current->euid != p->uid) &&
 133                                 !capable(CAP_SYS_PTRACE))
 134                         goto err_unlock;
 135                 head = p->compat_robust_list;
 136                 read_unlock(&tasklist_lock);
 137         }
 138
 139         if (put_user(sizeof(*head), len_ptr))
 140                 return -EFAULT;
 141         return put_user(ptr_to_compat(head), head_ptr);
 142
 143 err_unlock:
 144         read_unlock(&tasklist_lock);
 145
 146         return ret;
 147 }
 148
 149 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 150                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 151                 u32 val3)
 152 {
 153         struct timespec ts;
 154         ktime_t t, *tp = NULL;
 155         int val2 = 0;
 156         int cmd = op & FUTEX_CMD_MASK;
 157
 158         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) {
 159                 if (get_compat_timespec(&ts, utime))
 160                         return -EFAULT;
 161                 if (!timespec_valid(&ts))
 162                         return -EINVAL;
 163
 164                 t = timespec_to_ktime(ts);
 165                 if (cmd == FUTEX_WAIT)
 166                         t = ktime_add(ktime_get(), t);
 167                 tp = &t;
 168         }
 169         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
 170                 val2 = (int) (unsigned long) utime;
 171
 172         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 173 }