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(wq_head: &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(objp: 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(filp: file, wait_address: &current->sighand->signalfd_wqh, p: wait);
57
58 spin_lock_irq(lock: &current->sighand->siglock);
59 if (next_signal(pending: &current->pending, mask: &ctx->sigmask) ||
60 next_signal(pending: &current->signal->shared_pending,
61 mask: &ctx->sigmask))
62 events |= EPOLLIN;
63 spin_unlock_irq(lock: &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(sig: kinfo->si_signo, si_code: 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(to: uinfo, from: &new, n: 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(lock: &current->sighand->siglock);
163 ret = dequeue_signal(current, mask: &ctx->sigmask, info, type: &type);
164 switch (ret) {
165 case 0:
166 if (!nonblock)
167 break;
168 ret = -EAGAIN;
169 fallthrough;
170 default:
171 spin_unlock_irq(lock: &current->sighand->siglock);
172 return ret;
173 }
174
175 add_wait_queue(wq_head: &current->sighand->signalfd_wqh, wq_entry: &wait);
176 for (;;) {
177 set_current_state(TASK_INTERRUPTIBLE);
178 ret = dequeue_signal(current, mask: &ctx->sigmask, info, type: &type);
179 if (ret != 0)
180 break;
181 if (signal_pending(current)) {
182 ret = -ERESTARTSYS;
183 break;
184 }
185 spin_unlock_irq(lock: &current->sighand->siglock);
186 schedule();
187 spin_lock_irq(lock: &current->sighand->siglock);
188 }
189 spin_unlock_irq(lock: &current->sighand->siglock);
190
191 remove_wait_queue(wq_head: &current->sighand->signalfd_wqh, wq_entry: &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: &info, nonblock);
218 if (unlikely(ret <= 0))
219 break;
220 ret = signalfd_copyinfo(uinfo: siginfo, kinfo: &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(set: &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(set: mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
265 signotset(set: mask);
266
267 if (ufd == -1) {
268 ctx = kmalloc(size: 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(name: "[signalfd]", fops: &signalfd_fops, priv: ctx,
279 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
280 if (ufd < 0)
281 kfree(objp: ctx);
282 } else {
283 struct fd f = fdget(fd: ufd);
284 if (!f.file)
285 return -EBADF;
286 ctx = f.file->private_data;
287 if (f.file->f_op != &signalfd_fops) {
288 fdput(fd: f);
289 return -EINVAL;
290 }
291 spin_lock_irq(lock: &current->sighand->siglock);
292 ctx->sigmask = *mask;
293 spin_unlock_irq(lock: &current->sighand->siglock);
294
295 wake_up(&current->sighand->signalfd_wqh);
296 fdput(fd: 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(to: &mask, from: user_mask, n: sizeof(mask)))
310 return -EFAULT;
311 return do_signalfd4(ufd, mask: &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(to: &mask, from: user_mask, n: sizeof(mask)))
322 return -EFAULT;
323 return do_signalfd4(ufd, mask: &mask, flags: 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(set: &mask, compat: user_mask))
336 return -EFAULT;
337 return do_signalfd4(ufd, mask: &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, flags: 0);
353}
354#endif
355

source code of linux/fs/signalfd.c