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
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        rcu_read_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        rcu_read_unlock();
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    rcu_read_unlock();
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

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