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
fetch_robust_entry(compat_uptr_t * uentry,struct robust_list __user ** entry,compat_uptr_t __user * head,int * pi)21 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
22 compat_uptr_t __user *head, 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
futex_uaddr(struct robust_list __user * entry,compat_long_t futex_offset)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 */
compat_exit_robust_list(struct task_struct * curr)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, next_pi, pip;
53 compat_uptr_t uentry, next_uentry, upending;
54 compat_long_t futex_offset;
55 int rc;
56
57 if (!futex_cmpxchg_enabled)
58 return;
59
60 /*
61 * Fetch the list head (which was registered earlier, via
62 * sys_set_robust_list()):
63 */
64 if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
65 return;
66 /*
67 * Fetch the relative futex offset:
68 */
69 if (get_user(futex_offset, &head->futex_offset))
70 return;
71 /*
72 * Fetch any possibly pending lock-add first, and handle it
73 * if it exists:
74 */
75 if (fetch_robust_entry(&upending, &pending,
76 &head->list_op_pending, &pip))
77 return;
78
79 next_entry = NULL; /* avoid warning with gcc */
80 while (entry != (struct robust_list __user *) &head->list) {
81 /*
82 * Fetch the next entry in the list before calling
83 * handle_futex_death:
84 */
85 rc = fetch_robust_entry(&next_uentry, &next_entry,
86 (compat_uptr_t __user *)&entry->next, &next_pi);
87 /*
88 * A pending lock might already be on the list, so
89 * dont process it twice:
90 */
91 if (entry != pending) {
92 void __user *uaddr = futex_uaddr(entry, futex_offset);
93
94 if (handle_futex_death(uaddr, curr, pi))
95 return;
96 }
97 if (rc)
98 return;
99 uentry = next_uentry;
100 entry = next_entry;
101 pi = next_pi;
102 /*
103 * Avoid excessively long or circular lists:
104 */
105 if (!--limit)
106 break;
107
108 cond_resched();
109 }
110 if (pending) {
111 void __user *uaddr = futex_uaddr(pending, futex_offset);
112
113 handle_futex_death(uaddr, curr, pip);
114 }
115 }
116
117 asmlinkage long
compat_sys_set_robust_list(struct compat_robust_list_head __user * head,compat_size_t len)118 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
119 compat_size_t len)
120 {
121 if (!futex_cmpxchg_enabled)
122 return -ENOSYS;
123
124 if (unlikely(len != sizeof(*head)))
125 return -EINVAL;
126
127 current->compat_robust_list = head;
128
129 return 0;
130 }
131
132 asmlinkage long
compat_sys_get_robust_list(int pid,compat_uptr_t __user * head_ptr,compat_size_t __user * len_ptr)133 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
134 compat_size_t __user *len_ptr)
135 {
136 struct compat_robust_list_head __user *head;
137 unsigned long ret;
138 const struct cred *cred = current_cred(), *pcred;
139
140 if (!futex_cmpxchg_enabled)
141 return -ENOSYS;
142
143 if (!pid)
144 head = current->compat_robust_list;
145 else {
146 struct task_struct *p;
147
148 ret = -ESRCH;
149 read_lock(&tasklist_lock);
150 p = find_task_by_vpid(pid);
151 if (!p)
152 goto err_unlock;
153 ret = -EPERM;
154 pcred = __task_cred(p);
155 if (cred->euid != pcred->euid &&
156 cred->euid != pcred->uid &&
157 !capable(CAP_SYS_PTRACE))
158 goto err_unlock;
159 head = p->compat_robust_list;
160 read_unlock(&tasklist_lock);
161 }
162
163 if (put_user(sizeof(*head), len_ptr))
164 return -EFAULT;
165 return put_user(ptr_to_compat(head), head_ptr);
166
167 err_unlock:
168 read_unlock(&tasklist_lock);
169
170 return ret;
171 }
172
compat_sys_futex(u32 __user * uaddr,int op,u32 val,struct compat_timespec __user * utime,u32 __user * uaddr2,u32 val3)173 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
174 struct compat_timespec __user *utime, u32 __user *uaddr2,
175 u32 val3)
176 {
177 struct timespec ts;
178 ktime_t t, *tp = NULL;
179 int val2 = 0;
180 int cmd = op & FUTEX_CMD_MASK;
181
182 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
183 cmd == FUTEX_WAIT_BITSET)) {
184 if (get_compat_timespec(&ts, utime))
185 return -EFAULT;
186 if (!timespec_valid(&ts))
187 return -EINVAL;
188
189 t = timespec_to_ktime(ts);
190 if (cmd == FUTEX_WAIT)
191 t = ktime_add_safe(ktime_get(), t);
192 tp = &t;
193 }
194 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
195 val2 = (int) (unsigned long) utime;
196
197 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
198 }
199