projects/linux·blob v3.0 · refs

210 lines · 4.9 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
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}