linux/kernel/futex_compat.c
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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 */
  20static inline int
  21fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
  22                   compat_uptr_t __user *head, unsigned 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
  33static 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 */
  48void 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, pip;
  53        unsigned int uninitialized_var(next_pi);
  54        compat_uptr_t uentry, next_uentry, upending;
  55        compat_long_t futex_offset;
  56        int rc;
  57
  58        if (!futex_cmpxchg_enabled)
  59                return;
  60
  61        /*
  62         * Fetch the list head (which was registered earlier, via
  63         * sys_set_robust_list()):
  64         */
  65        if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  66                return;
  67        /*
  68         * Fetch the relative futex offset:
  69         */
  70        if (get_user(futex_offset, &head->futex_offset))
  71                return;
  72        /*
  73         * Fetch any possibly pending lock-add first, and handle it
  74         * if it exists:
  75         */
  76        if (fetch_robust_entry(&upending, &pending,
  77                               &head->list_op_pending, &pip))
  78                return;
  79
  80        next_entry = NULL;      /* avoid warning with gcc */
  81        while (entry != (struct robust_list __user *) &head->list) {
  82                /*
  83                 * Fetch the next entry in the list before calling
  84                 * handle_futex_death:
  85                 */
  86                rc = fetch_robust_entry(&next_uentry, &next_entry,
  87                        (compat_uptr_t __user *)&entry->next, &next_pi);
  88                /*
  89                 * A pending lock might already be on the list, so
  90                 * dont process it twice:
  91                 */
  92                if (entry != pending) {
  93                        void __user *uaddr = futex_uaddr(entry, futex_offset);
  94
  95                        if (handle_futex_death(uaddr, curr, pi))
  96                                return;
  97                }
  98                if (rc)
  99                        return;
 100                uentry = next_uentry;
 101                entry = next_entry;
 102                pi = next_pi;
 103                /*
 104                 * Avoid excessively long or circular lists:
 105                 */
 106                if (!--limit)
 107                        break;
 108
 109                cond_resched();
 110        }
 111        if (pending) {
 112                void __user *uaddr = futex_uaddr(pending, futex_offset);
 113
 114                handle_futex_death(uaddr, curr, pip);
 115        }
 116}
 117
 118asmlinkage long
 119compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 120                           compat_size_t len)
 121{
 122        if (!futex_cmpxchg_enabled)
 123                return -ENOSYS;
 124
 125        if (unlikely(len != sizeof(*head)))
 126                return -EINVAL;
 127
 128        current->compat_robust_list = head;
 129
 130        return 0;
 131}
 132
 133asmlinkage long
 134compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 135                           compat_size_t __user *len_ptr)
 136{
 137        struct compat_robust_list_head __user *head;
 138        unsigned long ret;
 139        const struct cred *cred = current_cred(), *pcred;
 140
 141        if (!futex_cmpxchg_enabled)
 142                return -ENOSYS;
 143
 144        if (!pid)
 145                head = current->compat_robust_list;
 146        else {
 147                struct task_struct *p;
 148
 149                ret = -ESRCH;
 150                rcu_read_lock();
 151                p = find_task_by_vpid(pid);
 152                if (!p)
 153                        goto err_unlock;
 154                ret = -EPERM;
 155                pcred = __task_cred(p);
 156                /* If victim is in different user_ns, then uids are not
 157                   comparable, so we must have CAP_SYS_PTRACE */
 158                if (cred->user->user_ns != pcred->user->user_ns) {
 159                        if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
 160                                goto err_unlock;
 161                        goto ok;
 162                }
 163                /* If victim is in same user_ns, then uids are comparable */
 164                if (cred->euid != pcred->euid &&
 165                    cred->euid != pcred->uid &&
 166                    !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
 167                        goto err_unlock;
 168ok:
 169                head = p->compat_robust_list;
 170                rcu_read_unlock();
 171        }
 172
 173        if (put_user(sizeof(*head), len_ptr))
 174                return -EFAULT;
 175        return put_user(ptr_to_compat(head), head_ptr);
 176
 177err_unlock:
 178        rcu_read_unlock();
 179
 180        return ret;
 181}
 182
 183asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 184                struct compat_timespec __user *utime, u32 __user *uaddr2,
 185                u32 val3)
 186{
 187        struct timespec ts;
 188        ktime_t t, *tp = NULL;
 189        int val2 = 0;
 190        int cmd = op & FUTEX_CMD_MASK;
 191
 192        if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
 193                      cmd == FUTEX_WAIT_BITSET ||
 194                      cmd == FUTEX_WAIT_REQUEUE_PI)) {
 195                if (get_compat_timespec(&ts, utime))
 196                        return -EFAULT;
 197                if (!timespec_valid(&ts))
 198                        return -EINVAL;
 199
 200                t = timespec_to_ktime(ts);
 201                if (cmd == FUTEX_WAIT)
 202                        t = ktime_add_safe(ktime_get(), t);
 203                tp = &t;
 204        }
 205        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
 206            cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
 207                val2 = (int) (unsigned long) utime;
 208
 209        return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 210}
 211
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