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, 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, 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
 117asmlinkage long
 118compat_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
 132asmlinkage long
 133compat_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
 167err_unlock:
 168        read_unlock(&tasklist_lock);
 169
 170        return ret;
 171}
 172
 173asmlinkage 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                      cmd == FUTEX_WAIT_REQUEUE_PI)) {
 185                if (get_compat_timespec(&ts, utime))
 186                        return -EFAULT;
 187                if (!timespec_valid(&ts))
 188                        return -EINVAL;
 189
 190                t = timespec_to_ktime(ts);
 191                if (cmd == FUTEX_WAIT)
 192                        t = ktime_add_safe(ktime_get(), t);
 193                tp = &t;
 194        }
 195        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
 196            cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
 197                val2 = (int) (unsigned long) utime;
 198
 199        return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 200}
 201