userns: user namespaces: convert several capable() calls
[linux-2.6.git] / 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  */
20 static inline int
21 fetch_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
33 static 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  */
48 void 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
118 asmlinkage long
119 compat_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
133 asmlinkage long
134 compat_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;
168 ok:
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
177 err_unlock:
178         rcu_read_unlock();
179
180         return ret;
181 }
182
183 asmlinkage 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 }