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 */
 23static inline int
 24fetch_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
 36static 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 */
 51void 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
121COMPAT_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
136COMPAT_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
169err_unlock:
170	rcu_read_unlock();
171
172	return ret;
173}
174
175COMPAT_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}