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 */
 20static inline int
 21fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
 22		   compat_uptr_t __user *head, unsigned 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
 33static 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 */
 48void 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, pip;
 53	unsigned int uninitialized_var(next_pi);
 54	compat_uptr_t uentry, next_uentry, upending;
 55	compat_long_t futex_offset;
 56	int rc;
 57
 58	if (!futex_cmpxchg_enabled)
 59		return;
 60
 61	/*
 62	 * Fetch the list head (which was registered earlier, via
 63	 * sys_set_robust_list()):
 64	 */
 65	if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
 66		return;
 67	/*
 68	 * Fetch the relative futex offset:
 69	 */
 70	if (get_user(futex_offset, &head->futex_offset))
 71		return;
 72	/*
 73	 * Fetch any possibly pending lock-add first, and handle it
 74	 * if it exists:
 75	 */
 76	if (fetch_robust_entry(&upending, &pending,
 77			       &head->list_op_pending, &pip))
 78		return;
 79
 80	next_entry = NULL;	/* avoid warning with gcc */
 81	while (entry != (struct robust_list __user *) &head->list) {
 82		/*
 83		 * Fetch the next entry in the list before calling
 84		 * handle_futex_death:
 85		 */
 86		rc = fetch_robust_entry(&next_uentry, &next_entry,
 87			(compat_uptr_t __user *)&entry->next, &next_pi);
 88		/*
 89		 * A pending lock might already be on the list, so
 90		 * dont process it twice:
 91		 */
 92		if (entry != pending) {
 93			void __user *uaddr = futex_uaddr(entry, futex_offset);
 94
 95			if (handle_futex_death(uaddr, curr, pi))
 96				return;
 97		}
 98		if (rc)
 99			return;
100		uentry = next_uentry;
101		entry = next_entry;
102		pi = next_pi;
103		/*
104		 * Avoid excessively long or circular lists:
105		 */
106		if (!--limit)
107			break;
108
109		cond_resched();
110	}
111	if (pending) {
112		void __user *uaddr = futex_uaddr(pending, futex_offset);
113
114		handle_futex_death(uaddr, curr, pip);
115	}
116}
117
118asmlinkage long
119compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
120			   compat_size_t len)
121{
122	if (!futex_cmpxchg_enabled)
123		return -ENOSYS;
124
125	if (unlikely(len != sizeof(*head)))
126		return -EINVAL;
127
128	current->compat_robust_list = head;
129
130	return 0;
131}
132
133asmlinkage long
134compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
135			   compat_size_t __user *len_ptr)
136{
137	struct compat_robust_list_head __user *head;
138	unsigned long ret;
139	const struct cred *cred = current_cred(), *pcred;
140
141	if (!futex_cmpxchg_enabled)
142		return -ENOSYS;
143
144	if (!pid)
145		head = current->compat_robust_list;
146	else {
147		struct task_struct *p;
148
149		ret = -ESRCH;
150		rcu_read_lock();
151		p = find_task_by_vpid(pid);
152		if (!p)
153			goto err_unlock;
154		ret = -EPERM;
155		pcred = __task_cred(p);
156		/* If victim is in different user_ns, then uids are not
157		   comparable, so we must have CAP_SYS_PTRACE */
158		if (cred->user->user_ns != pcred->user->user_ns) {
159			if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
160				goto err_unlock;
161			goto ok;
162		}
163		/* If victim is in same user_ns, then uids are comparable */
164		if (cred->euid != pcred->euid &&
165		    cred->euid != pcred->uid &&
166		    !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
167			goto err_unlock;
168ok:
169		head = p->compat_robust_list;
170		rcu_read_unlock();
171	}
172
173	if (put_user(sizeof(*head), len_ptr))
174		return -EFAULT;
175	return put_user(ptr_to_compat(head), head_ptr);
176
177err_unlock:
178	rcu_read_unlock();
179
180	return ret;
181}
182
183asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
184		struct compat_timespec __user *utime, u32 __user *uaddr2,
185		u32 val3)
186{
187	struct timespec ts;
188	ktime_t t, *tp = NULL;
189	int val2 = 0;
190	int cmd = op & FUTEX_CMD_MASK;
191
192	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
193		      cmd == FUTEX_WAIT_BITSET ||
194		      cmd == FUTEX_WAIT_REQUEUE_PI)) {
195		if (get_compat_timespec(&ts, utime))
196			return -EFAULT;
197		if (!timespec_valid(&ts))
198			return -EINVAL;
199
200		t = timespec_to_ktime(ts);
201		if (cmd == FUTEX_WAIT)
202			t = ktime_add_safe(ktime_get(), t);
203		tp = &t;
204	}
205	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
206	    cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
207		val2 = (int) (unsigned long) utime;
208
209	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
210}