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
fetch_robust_entry(compat_uptr_t * uentry,struct robust_list __user ** entry,compat_uptr_t __user * head,unsigned int * pi)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
futex_uaddr(struct robust_list __user * entry,compat_long_t futex_offset)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 */
compat_exit_robust_list(struct task_struct * curr)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
COMPAT_SYSCALL_DEFINE2(set_robust_list,struct compat_robust_list_head __user *,head,compat_size_t,len)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
COMPAT_SYSCALL_DEFINE3(get_robust_list,int,pid,compat_uptr_t __user *,head_ptr,compat_size_t __user *,len_ptr)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
COMPAT_SYSCALL_DEFINE6(futex,u32 __user *,uaddr,int,op,u32,val,struct compat_timespec __user *,utime,u32 __user *,uaddr2,u32,val3)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 }
203
