1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  fs/signalfd.c
4 *
5 *  Copyright (C) 2003  Linus Torvalds
6 *
7 *  Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
8 *      Changed ->read() to return a siginfo strcture instead of signal number.
9 *      Fixed locking in ->poll().
10 *      Added sighand-detach notification.
11 *      Added fd re-use in sys_signalfd() syscall.
12 *      Now using anonymous inode source.
13 *      Thanks to Oleg Nesterov for useful code review and suggestions.
14 *      More comments and suggestions from Arnd Bergmann.
15 *  Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
16 *      Retrieve multiple signals with one read() call
17 *  Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
18 *      Attach to the sighand only during read() and poll().
19 */
20
21#include <linux/file.h>
22#include <linux/poll.h>
23#include <linux/init.h>
24#include <linux/fs.h>
25#include <linux/sched.h>
26#include <linux/slab.h>
27#include <linux/kernel.h>
28#include <linux/signal.h>
29#include <linux/list.h>
30#include <linux/anon_inodes.h>
31#include <linux/signalfd.h>
32#include <linux/syscalls.h>
33#include <linux/proc_fs.h>
34#include <linux/compat.h>
35
36void signalfd_cleanup(struct sighand_struct *sighand)
37{
38	wake_up_pollfree(&sighand->signalfd_wqh);
39}
40
41struct signalfd_ctx {
42	sigset_t sigmask;
43};
44
45static int signalfd_release(struct inode *inode, struct file *file)
46{
47	kfree(file->private_data);
48	return 0;
49}
50
51static __poll_t signalfd_poll(struct file *file, poll_table *wait)
52{
53	struct signalfd_ctx *ctx = file->private_data;
54	__poll_t events = 0;
55
56	poll_wait(file, &current->sighand->signalfd_wqh, wait);
57
58	spin_lock_irq(&current->sighand->siglock);
59	if (next_signal(&current->pending, &ctx->sigmask) ||
60	    next_signal(&current->signal->shared_pending,
61			&ctx->sigmask))
62		events |= EPOLLIN;
63	spin_unlock_irq(&current->sighand->siglock);
64
65	return events;
66}
67
68/*
69 * Copied from copy_siginfo_to_user() in kernel/signal.c
70 */
71static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
72			     kernel_siginfo_t const *kinfo)
73{
74	struct signalfd_siginfo new;
75
76	BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
77
78	/*
79	 * Unused members should be zero ...
80	 */
81	memset(&new, 0, sizeof(new));
82
83	/*
84	 * If you change siginfo_t structure, please be sure
85	 * this code is fixed accordingly.
86	 */
87	new.ssi_signo = kinfo->si_signo;
88	new.ssi_errno = kinfo->si_errno;
89	new.ssi_code  = kinfo->si_code;
90	switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) {
91	case SIL_KILL:
92		new.ssi_pid = kinfo->si_pid;
93		new.ssi_uid = kinfo->si_uid;
94		break;
95	case SIL_TIMER:
96		new.ssi_tid = kinfo->si_tid;
97		new.ssi_overrun = kinfo->si_overrun;
98		new.ssi_ptr = (long) kinfo->si_ptr;
99		new.ssi_int = kinfo->si_int;
100		break;
101	case SIL_POLL:
102		new.ssi_band = kinfo->si_band;
103		new.ssi_fd   = kinfo->si_fd;
104		break;
105	case SIL_FAULT_BNDERR:
106	case SIL_FAULT_PKUERR:
107	case SIL_FAULT_PERF_EVENT:
108		/*
109		 * Fall through to the SIL_FAULT case.  SIL_FAULT_BNDERR,
110		 * SIL_FAULT_PKUERR, and SIL_FAULT_PERF_EVENT are only
111		 * generated by faults that deliver them synchronously to
112		 * userspace.  In case someone injects one of these signals
113		 * and signalfd catches it treat it as SIL_FAULT.
114		 */
115	case SIL_FAULT:
116		new.ssi_addr = (long) kinfo->si_addr;
117		break;
118	case SIL_FAULT_TRAPNO:
119		new.ssi_addr = (long) kinfo->si_addr;
120		new.ssi_trapno = kinfo->si_trapno;
121		break;
122	case SIL_FAULT_MCEERR:
123		new.ssi_addr = (long) kinfo->si_addr;
124		new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
125		break;
126	case SIL_CHLD:
127		new.ssi_pid    = kinfo->si_pid;
128		new.ssi_uid    = kinfo->si_uid;
129		new.ssi_status = kinfo->si_status;
130		new.ssi_utime  = kinfo->si_utime;
131		new.ssi_stime  = kinfo->si_stime;
132		break;
133	case SIL_RT:
134		/*
135		 * This case catches also the signals queued by sigqueue().
136		 */
137		new.ssi_pid = kinfo->si_pid;
138		new.ssi_uid = kinfo->si_uid;
139		new.ssi_ptr = (long) kinfo->si_ptr;
140		new.ssi_int = kinfo->si_int;
141		break;
142	case SIL_SYS:
143		new.ssi_call_addr = (long) kinfo->si_call_addr;
144		new.ssi_syscall   = kinfo->si_syscall;
145		new.ssi_arch      = kinfo->si_arch;
146		break;
147	}
148
149	if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
150		return -EFAULT;
151
152	return sizeof(*uinfo);
153}
154
155static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
156				int nonblock)
157{
158	enum pid_type type;
159	ssize_t ret;
160	DECLARE_WAITQUEUE(wait, current);
161
162	spin_lock_irq(&current->sighand->siglock);
163	ret = dequeue_signal(current, &ctx->sigmask, info, &type);
164	switch (ret) {
165	case 0:
166		if (!nonblock)
167			break;
168		ret = -EAGAIN;
169		fallthrough;
170	default:
171		spin_unlock_irq(&current->sighand->siglock);
172		return ret;
173	}
174
175	add_wait_queue(&current->sighand->signalfd_wqh, &wait);
176	for (;;) {
177		set_current_state(TASK_INTERRUPTIBLE);
178		ret = dequeue_signal(current, &ctx->sigmask, info, &type);
179		if (ret != 0)
180			break;
181		if (signal_pending(current)) {
182			ret = -ERESTARTSYS;
183			break;
184		}
185		spin_unlock_irq(&current->sighand->siglock);
186		schedule();
187		spin_lock_irq(&current->sighand->siglock);
188	}
189	spin_unlock_irq(&current->sighand->siglock);
190
191	remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
192	__set_current_state(TASK_RUNNING);
193
194	return ret;
195}
196
197/*
198 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
199 * error code. The "count" parameter must be at least the size of a
200 * "struct signalfd_siginfo".
201 */
202static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
203			     loff_t *ppos)
204{
205	struct signalfd_ctx *ctx = file->private_data;
206	struct signalfd_siginfo __user *siginfo;
207	int nonblock = file->f_flags & O_NONBLOCK;
208	ssize_t ret, total = 0;
209	kernel_siginfo_t info;
210
211	count /= sizeof(struct signalfd_siginfo);
212	if (!count)
213		return -EINVAL;
214
215	siginfo = (struct signalfd_siginfo __user *) buf;
216	do {
217		ret = signalfd_dequeue(ctx, &info, nonblock);
218		if (unlikely(ret <= 0))
219			break;
220		ret = signalfd_copyinfo(siginfo, &info);
221		if (ret < 0)
222			break;
223		siginfo++;
224		total += ret;
225		nonblock = 1;
226	} while (--count);
227
228	return total ? total: ret;
229}
230
231#ifdef CONFIG_PROC_FS
232static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
233{
234	struct signalfd_ctx *ctx = f->private_data;
235	sigset_t sigmask;
236
237	sigmask = ctx->sigmask;
238	signotset(&sigmask);
239	render_sigset_t(m, "sigmask:\t", &sigmask);
240}
241#endif
242
243static const struct file_operations signalfd_fops = {
244#ifdef CONFIG_PROC_FS
245	.show_fdinfo	= signalfd_show_fdinfo,
246#endif
247	.release	= signalfd_release,
248	.poll		= signalfd_poll,
249	.read		= signalfd_read,
250	.llseek		= noop_llseek,
251};
252
253static int do_signalfd4(int ufd, sigset_t *mask, int flags)
254{
255	struct signalfd_ctx *ctx;
256
257	/* Check the SFD_* constants for consistency.  */
258	BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
259	BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
260
261	if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
262		return -EINVAL;
263
264	sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
265	signotset(mask);
266
267	if (ufd == -1) {
268		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
269		if (!ctx)
270			return -ENOMEM;
271
272		ctx->sigmask = *mask;
273
274		/*
275		 * When we call this, the initialization must be complete, since
276		 * anon_inode_getfd() will install the fd.
277		 */
278		ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
279				       O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
280		if (ufd < 0)
281			kfree(ctx);
282	} else {
283		struct fd f = fdget(ufd);
284		if (!f.file)
285			return -EBADF;
286		ctx = f.file->private_data;
287		if (f.file->f_op != &signalfd_fops) {
288			fdput(f);
289			return -EINVAL;
290		}
291		spin_lock_irq(&current->sighand->siglock);
292		ctx->sigmask = *mask;
293		spin_unlock_irq(&current->sighand->siglock);
294
295		wake_up(&current->sighand->signalfd_wqh);
296		fdput(f);
297	}
298
299	return ufd;
300}
301
302SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
303		size_t, sizemask, int, flags)
304{
305	sigset_t mask;
306
307	if (sizemask != sizeof(sigset_t))
308		return -EINVAL;
309	if (copy_from_user(&mask, user_mask, sizeof(mask)))
310		return -EFAULT;
311	return do_signalfd4(ufd, &mask, flags);
312}
313
314SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
315		size_t, sizemask)
316{
317	sigset_t mask;
318
319	if (sizemask != sizeof(sigset_t))
320		return -EINVAL;
321	if (copy_from_user(&mask, user_mask, sizeof(mask)))
322		return -EFAULT;
323	return do_signalfd4(ufd, &mask, 0);
324}
325
326#ifdef CONFIG_COMPAT
327static long do_compat_signalfd4(int ufd,
328			const compat_sigset_t __user *user_mask,
329			compat_size_t sigsetsize, int flags)
330{
331	sigset_t mask;
332
333	if (sigsetsize != sizeof(compat_sigset_t))
334		return -EINVAL;
335	if (get_compat_sigset(&mask, user_mask))
336		return -EFAULT;
337	return do_signalfd4(ufd, &mask, flags);
338}
339
340COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
341		     const compat_sigset_t __user *, user_mask,
342		     compat_size_t, sigsetsize,
343		     int, flags)
344{
345	return do_compat_signalfd4(ufd, user_mask, sigsetsize, flags);
346}
347
348COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
349		     const compat_sigset_t __user *, user_mask,
350		     compat_size_t, sigsetsize)
351{
352	return do_compat_signalfd4(ufd, user_mask, sigsetsize, 0);
353}
354#endif
355