aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/futex_compat.c
blob: 2c2e2954b713b2681a5bf120c0097cb2c2affc8c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
/*
 * linux/kernel/futex_compat.c
 *
 * Futex compatibililty routines.
 *
 * Copyright 2006, Red Hat, Inc., Ingo Molnar
 */

#include <linux/linkage.h>
#include <linux/compat.h>
#include <linux/futex.h>

#include <asm/uaccess.h>


/*
 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
 */
static inline int
fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
		   compat_uptr_t __user *head, int *pi)
{
	if (get_user(*uentry, head))
		return -EFAULT;

	*entry = compat_ptr((*uentry) & ~1);
	*pi = (unsigned int)(*uentry) & 1;

	return 0;
}

/*
 * Walk curr->robust_list (very carefully, it's a userspace list!)
 * and mark any locks found there dead, and notify any waiters.
 *
 * We silently return on any sign of list-walking problem.
 */
void compat_exit_robust_list(struct task_struct *curr)
{
	struct compat_robust_list_head __user *head = curr->compat_robust_list;
	struct robust_list __user *entry, *next_entry, *pending;
	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
	compat_uptr_t uentry, next_uentry, upending;
	compat_long_t futex_offset;
	int rc;

	/*
	 * Fetch the list head (which was registered earlier, via
	 * sys_set_robust_list()):
	 */
	if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
		return;
	/*
	 * Fetch the relative futex offset:
	 */
	if (get_user(futex_offset, &head->futex_offset))
		return;
	/*
	 * Fetch any possibly pending lock-add first, and handle it
	 * if it exists:
	 */
	if (fetch_robust_entry(&upending, &pending,
			       &head->list_op_pending, &pip))
		return;

	next_entry = NULL;	/* avoid warning with gcc */
	while (entry != (struct robust_list __user *) &head->list) {
		/*
		 * Fetch the next entry in the list before calling
		 * handle_futex_death:
		 */
		rc = fetch_robust_entry(&next_uentry, &next_entry,
			(compat_uptr_t __user *)&entry->next, &next_pi);
		/*
		 * A pending lock might already be on the list, so
		 * dont process it twice:
		 */
		if (entry != pending)
			if (handle_futex_death((void __user *)entry + futex_offset,
						curr, pi))
				return;

		if (rc)
			return;
		uentry = next_uentry;
		entry = next_entry;
		pi = next_pi;
		/*
		 * Avoid excessively long or circular lists:
		 */
		if (!--limit)
			break;

		cond_resched();
	}
	if (pending)
		handle_futex_death((void __user *)pending + futex_offset,
				   curr, pip);
}

asmlinkage long
compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
			   compat_size_t len)
{
	if (unlikely(len != sizeof(*head)))
		return -EINVAL;

	current->compat_robust_list = head;

	return 0;
}

asmlinkage long
compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
			   compat_size_t __user *len_ptr)
{
	struct compat_robust_list_head __user *head;
	unsigned long ret;

	if (!pid)
		head = current->compat_robust_list;
	else {
		struct task_struct *p;

		ret = -ESRCH;
		read_lock(&tasklist_lock);
		p = find_task_by_pid(pid);
		if (!p)
			goto err_unlock;
		ret = -EPERM;
		if ((current->euid != p->euid) && (current->euid != p->uid) &&
				!capable(CAP_SYS_PTRACE))
			goto err_unlock;
		head = p->compat_robust_list;
		read_unlock(&tasklist_lock);
	}

	if (put_user(sizeof(*head), len_ptr))
		return -EFAULT;
	return put_user(ptr_to_compat(head), head_ptr);

err_unlock:
	read_unlock(&tasklist_lock);

	return ret;
}

asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
		struct compat_timespec __user *utime, u32 __user *uaddr2,
		u32 val3)
{
	struct timespec ts;
	ktime_t t, *tp = NULL;
	int val2 = 0;
	int cmd = op & FUTEX_CMD_MASK;

	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) {
		if (get_compat_timespec(&ts, utime))
			return -EFAULT;
		if (!timespec_valid(&ts))
			return -EINVAL;

		t = timespec_to_ktime(ts);
		if (cmd == FUTEX_WAIT)
			t = ktime_add(ktime_get(), t);
		tp = &t;
	}
	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
		val2 = (int) (unsigned long) utime;

	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}