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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 | ||
36 | void signalfd_cleanup(struct sighand_struct *sighand) | |
37 | { | |
38 | wait_queue_head_t *wqh = &sighand->signalfd_wqh; | |
39 | /* | |
40 | * The lockless check can race with remove_wait_queue() in progress, | |
41 | * but in this case its caller should run under rcu_read_lock() and | |
42 | * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return. | |
43 | */ | |
44 | if (likely(!waitqueue_active(wqh))) | |
45 | return; | |
46 | ||
47 | /* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */ | |
48 | wake_up_poll(wqh, POLLHUP | POLLFREE); | |
49 | } | |
50 | ||
51 | struct signalfd_ctx { | |
52 | sigset_t sigmask; | |
53 | }; | |
54 | ||
55 | static int signalfd_release(struct inode *inode, struct file *file) | |
56 | { | |
57 | kfree(file->private_data); | |
58 | return 0; | |
59 | } | |
60 | ||
61 | static unsigned int signalfd_poll(struct file *file, poll_table *wait) | |
62 | { | |
63 | struct signalfd_ctx *ctx = file->private_data; | |
64 | unsigned int events = 0; | |
65 | ||
66 | poll_wait(file, ¤t->sighand->signalfd_wqh, wait); | |
67 | ||
68 | spin_lock_irq(¤t->sighand->siglock); | |
69 | if (next_signal(¤t->pending, &ctx->sigmask) || | |
70 | next_signal(¤t->signal->shared_pending, | |
71 | &ctx->sigmask)) | |
72 | events |= POLLIN; | |
73 | spin_unlock_irq(¤t->sighand->siglock); | |
74 | ||
75 | return events; | |
76 | } | |
77 | ||
78 | /* | |
79 | * Copied from copy_siginfo_to_user() in kernel/signal.c | |
80 | */ | |
81 | static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, | |
82 | siginfo_t const *kinfo) | |
83 | { | |
84 | long err; | |
85 | ||
86 | BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); | |
87 | ||
88 | /* | |
89 | * Unused members should be zero ... | |
90 | */ | |
91 | err = __clear_user(uinfo, sizeof(*uinfo)); | |
92 | ||
93 | /* | |
94 | * If you change siginfo_t structure, please be sure | |
95 | * this code is fixed accordingly. | |
96 | */ | |
97 | err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo); | |
98 | err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno); | |
99 | err |= __put_user(kinfo->si_code, &uinfo->ssi_code); | |
100 | switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) { | |
101 | case SIL_KILL: | |
102 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); | |
103 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); | |
104 | break; | |
105 | case SIL_TIMER: | |
106 | err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid); | |
107 | err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun); | |
108 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); | |
109 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); | |
110 | break; | |
111 | case SIL_POLL: | |
112 | err |= __put_user(kinfo->si_band, &uinfo->ssi_band); | |
113 | err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd); | |
114 | break; | |
115 | case SIL_FAULT: | |
116 | err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr); | |
117 | #ifdef __ARCH_SI_TRAPNO | |
118 | err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno); | |
119 | #endif | |
120 | #ifdef BUS_MCEERR_AO | |
121 | /* | |
122 | * Other callers might not initialize the si_lsb field, | |
123 | * so check explicitly for the right codes here. | |
124 | */ | |
125 | if (kinfo->si_signo == SIGBUS && | |
126 | (kinfo->si_code == BUS_MCEERR_AR || | |
127 | kinfo->si_code == BUS_MCEERR_AO)) | |
128 | err |= __put_user((short) kinfo->si_addr_lsb, | |
129 | &uinfo->ssi_addr_lsb); | |
130 | #endif | |
131 | break; | |
132 | case SIL_CHLD: | |
133 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); | |
134 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); | |
135 | err |= __put_user(kinfo->si_status, &uinfo->ssi_status); | |
136 | err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); | |
137 | err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); | |
138 | break; | |
139 | case SIL_RT: | |
140 | default: | |
141 | /* | |
142 | * This case catches also the signals queued by sigqueue(). | |
143 | */ | |
144 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); | |
145 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); | |
146 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); | |
147 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); | |
148 | break; | |
149 | } | |
150 | ||
151 | return err ? -EFAULT: sizeof(*uinfo); | |
152 | } | |
153 | ||
154 | static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, | |
155 | int nonblock) | |
156 | { | |
157 | ssize_t ret; | |
158 | DECLARE_WAITQUEUE(wait, current); | |
159 | ||
160 | spin_lock_irq(¤t->sighand->siglock); | |
161 | ret = dequeue_signal(current, &ctx->sigmask, info); | |
162 | switch (ret) { | |
163 | case 0: | |
164 | if (!nonblock) | |
165 | break; | |
166 | ret = -EAGAIN; | |
167 | default: | |
168 | spin_unlock_irq(¤t->sighand->siglock); | |
169 | return ret; | |
170 | } | |
171 | ||
172 | add_wait_queue(¤t->sighand->signalfd_wqh, &wait); | |
173 | for (;;) { | |
174 | set_current_state(TASK_INTERRUPTIBLE); | |
175 | ret = dequeue_signal(current, &ctx->sigmask, info); | |
176 | if (ret != 0) | |
177 | break; | |
178 | if (signal_pending(current)) { | |
179 | ret = -ERESTARTSYS; | |
180 | break; | |
181 | } | |
182 | spin_unlock_irq(¤t->sighand->siglock); | |
183 | schedule(); | |
184 | spin_lock_irq(¤t->sighand->siglock); | |
185 | } | |
186 | spin_unlock_irq(¤t->sighand->siglock); | |
187 | ||
188 | remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); | |
189 | __set_current_state(TASK_RUNNING); | |
190 | ||
191 | return ret; | |
192 | } | |
193 | ||
194 | /* | |
195 | * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative | |
196 | * error code. The "count" parameter must be at least the size of a | |
197 | * "struct signalfd_siginfo". | |
198 | */ | |
199 | static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, | |
200 | loff_t *ppos) | |
201 | { | |
202 | struct signalfd_ctx *ctx = file->private_data; | |
203 | struct signalfd_siginfo __user *siginfo; | |
204 | int nonblock = file->f_flags & O_NONBLOCK; | |
205 | ssize_t ret, total = 0; | |
206 | siginfo_t info; | |
207 | ||
208 | count /= sizeof(struct signalfd_siginfo); | |
209 | if (!count) | |
210 | return -EINVAL; | |
211 | ||
212 | siginfo = (struct signalfd_siginfo __user *) buf; | |
213 | do { | |
214 | ret = signalfd_dequeue(ctx, &info, nonblock); | |
215 | if (unlikely(ret <= 0)) | |
216 | break; | |
217 | ret = signalfd_copyinfo(siginfo, &info); | |
218 | if (ret < 0) | |
219 | break; | |
220 | siginfo++; | |
221 | total += ret; | |
222 | nonblock = 1; | |
223 | } while (--count); | |
224 | ||
225 | return total ? total: ret; | |
226 | } | |
227 | ||
228 | #ifdef CONFIG_PROC_FS | |
229 | static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) | |
230 | { | |
231 | struct signalfd_ctx *ctx = f->private_data; | |
232 | sigset_t sigmask; | |
233 | ||
234 | sigmask = ctx->sigmask; | |
235 | signotset(&sigmask); | |
236 | render_sigset_t(m, "sigmask:\t", &sigmask); | |
237 | } | |
238 | #endif | |
239 | ||
240 | static const struct file_operations signalfd_fops = { | |
241 | #ifdef CONFIG_PROC_FS | |
242 | .show_fdinfo = signalfd_show_fdinfo, | |
243 | #endif | |
244 | .release = signalfd_release, | |
245 | .poll = signalfd_poll, | |
246 | .read = signalfd_read, | |
247 | .llseek = noop_llseek, | |
248 | }; | |
249 | ||
250 | SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, | |
251 | size_t, sizemask, int, flags) | |
252 | { | |
253 | sigset_t sigmask; | |
254 | struct signalfd_ctx *ctx; | |
255 | ||
256 | /* Check the SFD_* constants for consistency. */ | |
257 | BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); | |
258 | BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); | |
259 | ||
260 | if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) | |
261 | return -EINVAL; | |
262 | ||
263 | if (sizemask != sizeof(sigset_t) || | |
264 | copy_from_user(&sigmask, user_mask, sizeof(sigmask))) | |
265 | return -EINVAL; | |
266 | sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
267 | signotset(&sigmask); | |
268 | ||
269 | if (ufd == -1) { | |
270 | ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); | |
271 | if (!ctx) | |
272 | return -ENOMEM; | |
273 | ||
274 | ctx->sigmask = sigmask; | |
275 | ||
276 | /* | |
277 | * When we call this, the initialization must be complete, since | |
278 | * anon_inode_getfd() will install the fd. | |
279 | */ | |
280 | ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, | |
281 | O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); | |
282 | if (ufd < 0) | |
283 | kfree(ctx); | |
284 | } else { | |
285 | struct fd f = fdget(ufd); | |
286 | if (!f.file) | |
287 | return -EBADF; | |
288 | ctx = f.file->private_data; | |
289 | if (f.file->f_op != &signalfd_fops) { | |
290 | fdput(f); | |
291 | return -EINVAL; | |
292 | } | |
293 | spin_lock_irq(¤t->sighand->siglock); | |
294 | ctx->sigmask = sigmask; | |
295 | spin_unlock_irq(¤t->sighand->siglock); | |
296 | ||
297 | wake_up(¤t->sighand->signalfd_wqh); | |
298 | fdput(f); | |
299 | } | |
300 | ||
301 | return ufd; | |
302 | } | |
303 | ||
304 | SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, | |
305 | size_t, sizemask) | |
306 | { | |
307 | return sys_signalfd4(ufd, user_mask, sizemask, 0); | |
308 | } | |
309 | ||
310 | #ifdef CONFIG_COMPAT | |
311 | COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, | |
312 | const compat_sigset_t __user *,sigmask, | |
313 | compat_size_t, sigsetsize, | |
314 | int, flags) | |
315 | { | |
316 | sigset_t tmp; | |
317 | sigset_t __user *ksigmask; | |
318 | ||
319 | if (sigsetsize != sizeof(compat_sigset_t)) | |
320 | return -EINVAL; | |
321 | if (get_compat_sigset(&tmp, sigmask)) | |
322 | return -EFAULT; | |
323 | ksigmask = compat_alloc_user_space(sizeof(sigset_t)); | |
324 | if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) | |
325 | return -EFAULT; | |
326 | ||
327 | return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); | |
328 | } | |
329 | ||
330 | COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, | |
331 | const compat_sigset_t __user *,sigmask, | |
332 | compat_size_t, sigsetsize) | |
333 | { | |
334 | return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); | |
335 | } | |
336 | #endif |