projects/linux·blob v4.11 · refs

201 lines · 4.5 KiB

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#include <linux/syscalls.h>
15
16#include <linux/uaccess.h>
17
18
19/*
20 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
21 */
22static inline int
23fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
24 compat_uptr_t __user *head, unsigned int *pi)
25{
26 if (get_user(*uentry, head))
27 return -EFAULT;
28
29 *entry = compat_ptr((*uentry) & ~1);
30 *pi = (unsigned int)(*uentry) & 1;
31
32 return 0;
33}
34
35static void __user *futex_uaddr(struct robust_list __user *entry,
36 compat_long_t futex_offset)
37{
38 compat_uptr_t base = ptr_to_compat(entry);
39 void __user *uaddr = compat_ptr(base + futex_offset);
40
41 return uaddr;
42}
43
44/*
45 * Walk curr->robust_list (very carefully, it's a userspace list!)
46 * and mark any locks found there dead, and notify any waiters.
47 *
48 * We silently return on any sign of list-walking problem.
49 */
50void compat_exit_robust_list(struct task_struct *curr)
51{
52 struct compat_robust_list_head __user *head = curr->compat_robust_list;
53 struct robust_list __user *entry, *next_entry, *pending;
54 unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
55 unsigned int uninitialized_var(next_pi);
56 compat_uptr_t uentry, next_uentry, upending;
57 compat_long_t futex_offset;
58 int rc;
59
60 if (!futex_cmpxchg_enabled)
61 return;
62
63 /*
64 * Fetch the list head (which was registered earlier, via
65 * sys_set_robust_list()):
66 */
67 if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
68 return;
69 /*
70 * Fetch the relative futex offset:
71 */
72 if (get_user(futex_offset, &head->futex_offset))
73 return;
74 /*
75 * Fetch any possibly pending lock-add first, and handle it
76 * if it exists:
77 */
78 if (fetch_robust_entry(&upending, &pending,
79 &head->list_op_pending, &pip))
80 return;
81
82 next_entry = NULL; /* avoid warning with gcc */
83 while (entry != (struct robust_list __user *) &head->list) {
84 /*
85 * Fetch the next entry in the list before calling
86 * handle_futex_death:
87 */
88 rc = fetch_robust_entry(&next_uentry, &next_entry,
89 (compat_uptr_t __user *)&entry->next, &next_pi);
90 /*
91 * A pending lock might already be on the list, so
92 * dont process it twice:
93 */
94 if (entry != pending) {
95 void __user *uaddr = futex_uaddr(entry, futex_offset);
96
97 if (handle_futex_death(uaddr, curr, pi))
98 return;
99 }
100 if (rc)
101 return;
102 uentry = next_uentry;
103 entry = next_entry;
104 pi = next_pi;
105 /*
106 * Avoid excessively long or circular lists:
107 */
108 if (!--limit)
109 break;
110
111 cond_resched();
112 }
113 if (pending) {
114 void __user *uaddr = futex_uaddr(pending, futex_offset);
115
116 handle_futex_death(uaddr, curr, pip);
117 }
118}
119
120COMPAT_SYSCALL_DEFINE2(set_robust_list,
121 struct compat_robust_list_head __user *, head,
122 compat_size_t, len)
123{
124 if (!futex_cmpxchg_enabled)
125 return -ENOSYS;
126
127 if (unlikely(len != sizeof(*head)))
128 return -EINVAL;
129
130 current->compat_robust_list = head;
131
132 return 0;
133}
134
135COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
136 compat_uptr_t __user *, head_ptr,
137 compat_size_t __user *, len_ptr)
138{
139 struct compat_robust_list_head __user *head;
140 unsigned long ret;
141 struct task_struct *p;
142
143 if (!futex_cmpxchg_enabled)
144 return -ENOSYS;
145
146 rcu_read_lock();
147
148 ret = -ESRCH;
149 if (!pid)
150 p = current;
151 else {
152 p = find_task_by_vpid(pid);
153 if (!p)
154 goto err_unlock;
155 }
156
157 ret = -EPERM;
158 if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
159 goto err_unlock;
160
161 head = p->compat_robust_list;
162 rcu_read_unlock();
163
164 if (put_user(sizeof(*head), len_ptr))
165 return -EFAULT;
166 return put_user(ptr_to_compat(head), head_ptr);
167
168err_unlock:
169 rcu_read_unlock();
170
171 return ret;
172}
173
174COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
175 struct compat_timespec __user *, utime, u32 __user *, uaddr2,
176 u32, val3)
177{
178 struct timespec ts;
179 ktime_t t, *tp = NULL;
180 int val2 = 0;
181 int cmd = op & FUTEX_CMD_MASK;
182
183 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
184 cmd == FUTEX_WAIT_BITSET ||
185 cmd == FUTEX_WAIT_REQUEUE_PI)) {
186 if (compat_get_timespec(&ts, utime))
187 return -EFAULT;
188 if (!timespec_valid(&ts))
189 return -EINVAL;
190
191 t = timespec_to_ktime(ts);
192 if (cmd == FUTEX_WAIT)
193 t = ktime_add_safe(ktime_get(), t);
194 tp = &t;
195 }
196 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
197 cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
198 val2 = (int) (unsigned long) utime;
199
200 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
201}