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