Root/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
15#include <asm/uaccess.h>
16
17
18/*
19 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
20 */
21static inline int
22fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
23           compat_uptr_t __user *head, unsigned int *pi)
24{
25    if (get_user(*uentry, head))
26        return -EFAULT;
27
28    *entry = compat_ptr((*uentry) & ~1);
29    *pi = (unsigned int)(*uentry) & 1;
30
31    return 0;
32}
33
34static void __user *futex_uaddr(struct robust_list __user *entry,
35                compat_long_t futex_offset)
36{
37    compat_uptr_t base = ptr_to_compat(entry);
38    void __user *uaddr = compat_ptr(base + futex_offset);
39
40    return uaddr;
41}
42
43/*
44 * Walk curr->robust_list (very carefully, it's a userspace list!)
45 * and mark any locks found there dead, and notify any waiters.
46 *
47 * We silently return on any sign of list-walking problem.
48 */
49void compat_exit_robust_list(struct task_struct *curr)
50{
51    struct compat_robust_list_head __user *head = curr->compat_robust_list;
52    struct robust_list __user *entry, *next_entry, *pending;
53    unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
54    unsigned int uninitialized_var(next_pi);
55    compat_uptr_t uentry, next_uentry, upending;
56    compat_long_t futex_offset;
57    int rc;
58
59    if (!futex_cmpxchg_enabled)
60        return;
61
62    /*
63     * Fetch the list head (which was registered earlier, via
64     * sys_set_robust_list()):
65     */
66    if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
67        return;
68    /*
69     * Fetch the relative futex offset:
70     */
71    if (get_user(futex_offset, &head->futex_offset))
72        return;
73    /*
74     * Fetch any possibly pending lock-add first, and handle it
75     * if it exists:
76     */
77    if (fetch_robust_entry(&upending, &pending,
78                   &head->list_op_pending, &pip))
79        return;
80
81    next_entry = NULL; /* avoid warning with gcc */
82    while (entry != (struct robust_list __user *) &head->list) {
83        /*
84         * Fetch the next entry in the list before calling
85         * handle_futex_death:
86         */
87        rc = fetch_robust_entry(&next_uentry, &next_entry,
88            (compat_uptr_t __user *)&entry->next, &next_pi);
89        /*
90         * A pending lock might already be on the list, so
91         * dont process it twice:
92         */
93        if (entry != pending) {
94            void __user *uaddr = futex_uaddr(entry, futex_offset);
95
96            if (handle_futex_death(uaddr, curr, pi))
97                return;
98        }
99        if (rc)
100            return;
101        uentry = next_uentry;
102        entry = next_entry;
103        pi = next_pi;
104        /*
105         * Avoid excessively long or circular lists:
106         */
107        if (!--limit)
108            break;
109
110        cond_resched();
111    }
112    if (pending) {
113        void __user *uaddr = futex_uaddr(pending, futex_offset);
114
115        handle_futex_death(uaddr, curr, pip);
116    }
117}
118
119asmlinkage long
120compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
121               compat_size_t len)
122{
123    if (!futex_cmpxchg_enabled)
124        return -ENOSYS;
125
126    if (unlikely(len != sizeof(*head)))
127        return -EINVAL;
128
129    current->compat_robust_list = head;
130
131    return 0;
132}
133
134asmlinkage long
135compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
136               compat_size_t __user *len_ptr)
137{
138    struct compat_robust_list_head __user *head;
139    unsigned long ret;
140    struct task_struct *p;
141
142    if (!futex_cmpxchg_enabled)
143        return -ENOSYS;
144
145    WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
146
147    rcu_read_lock();
148
149    ret = -ESRCH;
150    if (!pid)
151        p = current;
152    else {
153        p = find_task_by_vpid(pid);
154        if (!p)
155            goto err_unlock;
156    }
157
158    ret = -EPERM;
159    if (!ptrace_may_access(p, PTRACE_MODE_READ))
160        goto err_unlock;
161
162    head = p->compat_robust_list;
163    rcu_read_unlock();
164
165    if (put_user(sizeof(*head), len_ptr))
166        return -EFAULT;
167    return put_user(ptr_to_compat(head), head_ptr);
168
169err_unlock:
170    rcu_read_unlock();
171
172    return ret;
173}
174
175asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
176        struct compat_timespec __user *utime, u32 __user *uaddr2,
177        u32 val3)
178{
179    struct timespec ts;
180    ktime_t t, *tp = NULL;
181    int val2 = 0;
182    int cmd = op & FUTEX_CMD_MASK;
183
184    if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
185              cmd == FUTEX_WAIT_BITSET ||
186              cmd == FUTEX_WAIT_REQUEUE_PI)) {
187        if (get_compat_timespec(&ts, utime))
188            return -EFAULT;
189        if (!timespec_valid(&ts))
190            return -EINVAL;
191
192        t = timespec_to_ktime(ts);
193        if (cmd == FUTEX_WAIT)
194            t = ktime_add_safe(ktime_get(), t);
195        tp = &t;
196    }
197    if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
198        cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
199        val2 = (int) (unsigned long) utime;
200
201    return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
202}
203

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