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, 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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