Merge branch 'work.sock_recvmsg' of git://git.kernel.org/pub/scm/linux/kernel/git...
[sfrench/cifs-2.6.git] / kernel / futex_compat.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * linux/kernel/futex_compat.c
4  *
5  * Futex compatibililty routines.
6  *
7  * Copyright 2006, Red Hat, Inc., Ingo Molnar
8  */
9
10 #include <linux/linkage.h>
11 #include <linux/compat.h>
12 #include <linux/nsproxy.h>
13 #include <linux/futex.h>
14 #include <linux/ptrace.h>
15 #include <linux/syscalls.h>
16
17 #include <linux/uaccess.h>
18
19
20 /*
21  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
22  */
23 static inline int
24 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
25                    compat_uptr_t __user *head, unsigned int *pi)
26 {
27         if (get_user(*uentry, head))
28                 return -EFAULT;
29
30         *entry = compat_ptr((*uentry) & ~1);
31         *pi = (unsigned int)(*uentry) & 1;
32
33         return 0;
34 }
35
36 static void __user *futex_uaddr(struct robust_list __user *entry,
37                                 compat_long_t futex_offset)
38 {
39         compat_uptr_t base = ptr_to_compat(entry);
40         void __user *uaddr = compat_ptr(base + futex_offset);
41
42         return uaddr;
43 }
44
45 /*
46  * Walk curr->robust_list (very carefully, it's a userspace list!)
47  * and mark any locks found there dead, and notify any waiters.
48  *
49  * We silently return on any sign of list-walking problem.
50  */
51 void compat_exit_robust_list(struct task_struct *curr)
52 {
53         struct compat_robust_list_head __user *head = curr->compat_robust_list;
54         struct robust_list __user *entry, *next_entry, *pending;
55         unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
56         unsigned int uninitialized_var(next_pi);
57         compat_uptr_t uentry, next_uentry, upending;
58         compat_long_t futex_offset;
59         int rc;
60
61         if (!futex_cmpxchg_enabled)
62                 return;
63
64         /*
65          * Fetch the list head (which was registered earlier, via
66          * sys_set_robust_list()):
67          */
68         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
69                 return;
70         /*
71          * Fetch the relative futex offset:
72          */
73         if (get_user(futex_offset, &head->futex_offset))
74                 return;
75         /*
76          * Fetch any possibly pending lock-add first, and handle it
77          * if it exists:
78          */
79         if (fetch_robust_entry(&upending, &pending,
80                                &head->list_op_pending, &pip))
81                 return;
82
83         next_entry = NULL;      /* avoid warning with gcc */
84         while (entry != (struct robust_list __user *) &head->list) {
85                 /*
86                  * Fetch the next entry in the list before calling
87                  * handle_futex_death:
88                  */
89                 rc = fetch_robust_entry(&next_uentry, &next_entry,
90                         (compat_uptr_t __user *)&entry->next, &next_pi);
91                 /*
92                  * A pending lock might already be on the list, so
93                  * dont process it twice:
94                  */
95                 if (entry != pending) {
96                         void __user *uaddr = futex_uaddr(entry, futex_offset);
97
98                         if (handle_futex_death(uaddr, curr, pi))
99                                 return;
100                 }
101                 if (rc)
102                         return;
103                 uentry = next_uentry;
104                 entry = next_entry;
105                 pi = next_pi;
106                 /*
107                  * Avoid excessively long or circular lists:
108                  */
109                 if (!--limit)
110                         break;
111
112                 cond_resched();
113         }
114         if (pending) {
115                 void __user *uaddr = futex_uaddr(pending, futex_offset);
116
117                 handle_futex_death(uaddr, curr, pip);
118         }
119 }
120
121 COMPAT_SYSCALL_DEFINE2(set_robust_list,
122                 struct compat_robust_list_head __user *, head,
123                 compat_size_t, len)
124 {
125         if (!futex_cmpxchg_enabled)
126                 return -ENOSYS;
127
128         if (unlikely(len != sizeof(*head)))
129                 return -EINVAL;
130
131         current->compat_robust_list = head;
132
133         return 0;
134 }
135
136 COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
137                         compat_uptr_t __user *, head_ptr,
138                         compat_size_t __user *, len_ptr)
139 {
140         struct compat_robust_list_head __user *head;
141         unsigned long ret;
142         struct task_struct *p;
143
144         if (!futex_cmpxchg_enabled)
145                 return -ENOSYS;
146
147         rcu_read_lock();
148
149         ret = -ESRCH;
150         if (!pid)
151                 p = current;
152         else {
153                 p = find_task_by_vpid(pid);
154                 if (!p)
155                         goto err_unlock;
156         }
157
158         ret = -EPERM;
159         if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
160                 goto err_unlock;
161
162         head = p->compat_robust_list;
163         rcu_read_unlock();
164
165         if (put_user(sizeof(*head), len_ptr))
166                 return -EFAULT;
167         return put_user(ptr_to_compat(head), head_ptr);
168
169 err_unlock:
170         rcu_read_unlock();
171
172         return ret;
173 }
174
175 COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
176                 struct compat_timespec __user *, utime, u32 __user *, uaddr2,
177                 u32, val3)
178 {
179         struct timespec ts;
180         ktime_t t, *tp = NULL;
181         int val2 = 0;
182         int cmd = op & FUTEX_CMD_MASK;
183
184         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
185                       cmd == FUTEX_WAIT_BITSET ||
186                       cmd == FUTEX_WAIT_REQUEUE_PI)) {
187                 if (compat_get_timespec(&ts, utime))
188                         return -EFAULT;
189                 if (!timespec_valid(&ts))
190                         return -EINVAL;
191
192                 t = timespec_to_ktime(ts);
193                 if (cmd == FUTEX_WAIT)
194                         t = ktime_add_safe(ktime_get(), t);
195                 tp = &t;
196         }
197         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
198             cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
199                 val2 = (int) (unsigned long) utime;
200
201         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
202 }