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 iov_iter *to, kernel_siginfo_t const *kinfo)
72{
73	struct signalfd_siginfo new;
74
75	BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
76
77	/*
78	 * Unused members should be zero ...
79	 */
80	memset(&new, 0, sizeof(new));
81
82	/*
83	 * If you change siginfo_t structure, please be sure
84	 * this code is fixed accordingly.
85	 */
86	new.ssi_signo = kinfo->si_signo;
87	new.ssi_errno = kinfo->si_errno;
88	new.ssi_code  = kinfo->si_code;
89	switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) {
90	case SIL_KILL:
91		new.ssi_pid = kinfo->si_pid;
92		new.ssi_uid = kinfo->si_uid;
93		break;
94	case SIL_TIMER:
95		new.ssi_tid = kinfo->si_tid;
96		new.ssi_overrun = kinfo->si_overrun;
97		new.ssi_ptr = (long) kinfo->si_ptr;
98		new.ssi_int = kinfo->si_int;
99		break;
100	case SIL_POLL:
101		new.ssi_band = kinfo->si_band;
102		new.ssi_fd   = kinfo->si_fd;
103		break;
104	case SIL_FAULT_BNDERR:
105	case SIL_FAULT_PKUERR:
106	case SIL_FAULT_PERF_EVENT:
107		/*
108		 * Fall through to the SIL_FAULT case.  SIL_FAULT_BNDERR,
109		 * SIL_FAULT_PKUERR, and SIL_FAULT_PERF_EVENT are only
110		 * generated by faults that deliver them synchronously to
111		 * userspace.  In case someone injects one of these signals
112		 * and signalfd catches it treat it as SIL_FAULT.
113		 */
114	case SIL_FAULT:
115		new.ssi_addr = (long) kinfo->si_addr;
116		break;
117	case SIL_FAULT_TRAPNO:
118		new.ssi_addr = (long) kinfo->si_addr;
119		new.ssi_trapno = kinfo->si_trapno;
120		break;
121	case SIL_FAULT_MCEERR:
122		new.ssi_addr = (long) kinfo->si_addr;
123		new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
124		break;
125	case SIL_CHLD:
126		new.ssi_pid    = kinfo->si_pid;
127		new.ssi_uid    = kinfo->si_uid;
128		new.ssi_status = kinfo->si_status;
129		new.ssi_utime  = kinfo->si_utime;
130		new.ssi_stime  = kinfo->si_stime;
131		break;
132	case SIL_RT:
133		/*
134		 * This case catches also the signals queued by sigqueue().
135		 */
136		new.ssi_pid = kinfo->si_pid;
137		new.ssi_uid = kinfo->si_uid;
138		new.ssi_ptr = (long) kinfo->si_ptr;
139		new.ssi_int = kinfo->si_int;
140		break;
141	case SIL_SYS:
142		new.ssi_call_addr = (long) kinfo->si_call_addr;
143		new.ssi_syscall   = kinfo->si_syscall;
144		new.ssi_arch      = kinfo->si_arch;
145		break;
146	}
147
148	if (!copy_to_iter_full(&new, sizeof(struct signalfd_siginfo), to))
149		return -EFAULT;
150
151	return sizeof(struct signalfd_siginfo);
152}
153
154static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
155				int nonblock)
156{
157	enum pid_type type;
158	ssize_t ret;
159	DECLARE_WAITQUEUE(wait, current);
160
161	spin_lock_irq(&current->sighand->siglock);
162	ret = dequeue_signal(current, &ctx->sigmask, info, &type);
163	switch (ret) {
164	case 0:
165		if (!nonblock)
166			break;
167		ret = -EAGAIN;
168		fallthrough;
169	default:
170		spin_unlock_irq(&current->sighand->siglock);
171		return ret;
172	}
173
174	add_wait_queue(&current->sighand->signalfd_wqh, &wait);
175	for (;;) {
176		set_current_state(TASK_INTERRUPTIBLE);
177		ret = dequeue_signal(current, &ctx->sigmask, info, &type);
178		if (ret != 0)
179			break;
180		if (signal_pending(current)) {
181			ret = -ERESTARTSYS;
182			break;
183		}
184		spin_unlock_irq(&current->sighand->siglock);
185		schedule();
186		spin_lock_irq(&current->sighand->siglock);
187	}
188	spin_unlock_irq(&current->sighand->siglock);
189
190	remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
191	__set_current_state(TASK_RUNNING);
192
193	return ret;
194}
195
196/*
197 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
198 * error code. The "count" parameter must be at least the size of a
199 * "struct signalfd_siginfo".
200 */
201static ssize_t signalfd_read_iter(struct kiocb *iocb, struct iov_iter *to)
202{
203	struct file *file = iocb->ki_filp;
204	struct signalfd_ctx *ctx = file->private_data;
205	size_t count = iov_iter_count(to);
206	ssize_t ret, total = 0;
207	kernel_siginfo_t info;
208	bool nonblock;
209
210	count /= sizeof(struct signalfd_siginfo);
211	if (!count)
212		return -EINVAL;
213
214	nonblock = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
215	do {
216		ret = signalfd_dequeue(ctx, &info, nonblock);
217		if (unlikely(ret <= 0))
218			break;
219		ret = signalfd_copyinfo(to, &info);
220		if (ret < 0)
221			break;
222		total += ret;
223		nonblock = 1;
224	} while (--count);
225
226	return total ? total: ret;
227}
228
229#ifdef CONFIG_PROC_FS
230static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
231{
232	struct signalfd_ctx *ctx = f->private_data;
233	sigset_t sigmask;
234
235	sigmask = ctx->sigmask;
236	signotset(&sigmask);
237	render_sigset_t(m, "sigmask:\t", &sigmask);
238}
239#endif
240
241static const struct file_operations signalfd_fops = {
242#ifdef CONFIG_PROC_FS
243	.show_fdinfo	= signalfd_show_fdinfo,
244#endif
245	.release	= signalfd_release,
246	.poll		= signalfd_poll,
247	.read_iter	= signalfd_read_iter,
248	.llseek		= noop_llseek,
249};
250
251static int do_signalfd4(int ufd, sigset_t *mask, int flags)
252{
253	struct signalfd_ctx *ctx;
254
255	/* Check the SFD_* constants for consistency.  */
256	BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
257	BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
258
259	if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
260		return -EINVAL;
261
262	sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
263	signotset(mask);
264
265	if (ufd == -1) {
266		struct file *file;
267
268		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
269		if (!ctx)
270			return -ENOMEM;
271
272		ctx->sigmask = *mask;
273
274		ufd = get_unused_fd_flags(flags & O_CLOEXEC);
275		if (ufd < 0) {
276			kfree(ctx);
277			return ufd;
278		}
279
280		file = anon_inode_getfile("[signalfd]", &signalfd_fops, ctx,
281				       O_RDWR | (flags & O_NONBLOCK));
282		if (IS_ERR(file)) {
283			put_unused_fd(ufd);
284			kfree(ctx);
285			return PTR_ERR(file);
286		}
287		file->f_mode |= FMODE_NOWAIT;
288
289		fd_install(ufd, file);
290	} else {
291		struct fd f = fdget(ufd);
292		if (!f.file)
293			return -EBADF;
294		ctx = f.file->private_data;
295		if (f.file->f_op != &signalfd_fops) {
296			fdput(f);
297			return -EINVAL;
298		}
299		spin_lock_irq(&current->sighand->siglock);
300		ctx->sigmask = *mask;
301		spin_unlock_irq(&current->sighand->siglock);
302
303		wake_up(&current->sighand->signalfd_wqh);
304		fdput(f);
305	}
306
307	return ufd;
308}
309
310SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
311		size_t, sizemask, int, flags)
312{
313	sigset_t mask;
314
315	if (sizemask != sizeof(sigset_t))
316		return -EINVAL;
317	if (copy_from_user(&mask, user_mask, sizeof(mask)))
318		return -EFAULT;
319	return do_signalfd4(ufd, &mask, flags);
320}
321
322SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
323		size_t, sizemask)
324{
325	sigset_t mask;
326
327	if (sizemask != sizeof(sigset_t))
328		return -EINVAL;
329	if (copy_from_user(&mask, user_mask, sizeof(mask)))
330		return -EFAULT;
331	return do_signalfd4(ufd, &mask, 0);
332}
333
334#ifdef CONFIG_COMPAT
335static long do_compat_signalfd4(int ufd,
336			const compat_sigset_t __user *user_mask,
337			compat_size_t sigsetsize, int flags)
338{
339	sigset_t mask;
340
341	if (sigsetsize != sizeof(compat_sigset_t))
342		return -EINVAL;
343	if (get_compat_sigset(&mask, user_mask))
344		return -EFAULT;
345	return do_signalfd4(ufd, &mask, flags);
346}
347
348COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
349		     const compat_sigset_t __user *, user_mask,
350		     compat_size_t, sigsetsize,
351		     int, flags)
352{
353	return do_compat_signalfd4(ufd, user_mask, sigsetsize, flags);
354}
355
356COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
357		     const compat_sigset_t __user *, user_mask,
358		     compat_size_t, sigsetsize)
359{
360	return do_compat_signalfd4(ufd, user_mask, sigsetsize, 0);
361}
362#endif
363