Line data Source code
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 :
36 367 : void signalfd_cleanup(struct sighand_struct *sighand)
37 : {
38 734 : wake_up_pollfree(&sighand->signalfd_wqh);
39 367 : }
40 :
41 : struct signalfd_ctx {
42 : sigset_t sigmask;
43 : };
44 :
45 0 : static int signalfd_release(struct inode *inode, struct file *file)
46 : {
47 0 : kfree(file->private_data);
48 0 : return 0;
49 : }
50 :
51 0 : static __poll_t signalfd_poll(struct file *file, poll_table *wait)
52 : {
53 0 : struct signalfd_ctx *ctx = file->private_data;
54 0 : __poll_t events = 0;
55 :
56 0 : poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
57 :
58 0 : spin_lock_irq(¤t->sighand->siglock);
59 0 : if (next_signal(¤t->pending, &ctx->sigmask) ||
60 0 : next_signal(¤t->signal->shared_pending,
61 : &ctx->sigmask))
62 : events |= EPOLLIN;
63 0 : spin_unlock_irq(¤t->sighand->siglock);
64 :
65 0 : return events;
66 : }
67 :
68 : /*
69 : * Copied from copy_siginfo_to_user() in kernel/signal.c
70 : */
71 0 : static 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 0 : 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 0 : new.ssi_signo = kinfo->si_signo;
88 0 : new.ssi_errno = kinfo->si_errno;
89 0 : new.ssi_code = kinfo->si_code;
90 0 : switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) {
91 : case SIL_KILL:
92 0 : new.ssi_pid = kinfo->si_pid;
93 0 : new.ssi_uid = kinfo->si_uid;
94 0 : break;
95 : case SIL_TIMER:
96 0 : new.ssi_tid = kinfo->si_tid;
97 0 : new.ssi_overrun = kinfo->si_overrun;
98 0 : new.ssi_ptr = (long) kinfo->si_ptr;
99 0 : new.ssi_int = kinfo->si_int;
100 0 : break;
101 : case SIL_POLL:
102 0 : new.ssi_band = kinfo->si_band;
103 0 : new.ssi_fd = kinfo->si_fd;
104 0 : 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 0 : new.ssi_addr = (long) kinfo->si_addr;
117 0 : break;
118 : case SIL_FAULT_TRAPNO:
119 0 : new.ssi_addr = (long) kinfo->si_addr;
120 0 : new.ssi_trapno = kinfo->si_trapno;
121 0 : break;
122 : case SIL_FAULT_MCEERR:
123 0 : new.ssi_addr = (long) kinfo->si_addr;
124 0 : new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
125 0 : break;
126 : case SIL_CHLD:
127 0 : new.ssi_pid = kinfo->si_pid;
128 0 : new.ssi_uid = kinfo->si_uid;
129 0 : new.ssi_status = kinfo->si_status;
130 0 : new.ssi_utime = kinfo->si_utime;
131 0 : new.ssi_stime = kinfo->si_stime;
132 0 : break;
133 : case SIL_RT:
134 : /*
135 : * This case catches also the signals queued by sigqueue().
136 : */
137 0 : new.ssi_pid = kinfo->si_pid;
138 0 : new.ssi_uid = kinfo->si_uid;
139 0 : new.ssi_ptr = (long) kinfo->si_ptr;
140 0 : new.ssi_int = kinfo->si_int;
141 0 : break;
142 : case SIL_SYS:
143 0 : new.ssi_call_addr = (long) kinfo->si_call_addr;
144 0 : new.ssi_syscall = kinfo->si_syscall;
145 0 : new.ssi_arch = kinfo->si_arch;
146 0 : break;
147 : }
148 :
149 0 : if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
150 : return -EFAULT;
151 :
152 0 : return sizeof(*uinfo);
153 : }
154 :
155 0 : static 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 0 : DECLARE_WAITQUEUE(wait, current);
161 :
162 0 : spin_lock_irq(¤t->sighand->siglock);
163 0 : ret = dequeue_signal(current, &ctx->sigmask, info, &type);
164 0 : switch (ret) {
165 : case 0:
166 0 : if (!nonblock)
167 : break;
168 : ret = -EAGAIN;
169 : fallthrough;
170 : default:
171 0 : spin_unlock_irq(¤t->sighand->siglock);
172 0 : return ret;
173 : }
174 :
175 0 : add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
176 : for (;;) {
177 0 : set_current_state(TASK_INTERRUPTIBLE);
178 0 : ret = dequeue_signal(current, &ctx->sigmask, info, &type);
179 0 : if (ret != 0)
180 : break;
181 0 : if (signal_pending(current)) {
182 : ret = -ERESTARTSYS;
183 : break;
184 : }
185 0 : spin_unlock_irq(¤t->sighand->siglock);
186 0 : schedule();
187 0 : spin_lock_irq(¤t->sighand->siglock);
188 : }
189 0 : spin_unlock_irq(¤t->sighand->siglock);
190 :
191 0 : remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
192 0 : __set_current_state(TASK_RUNNING);
193 :
194 0 : 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 : */
202 0 : static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
203 : loff_t *ppos)
204 : {
205 0 : struct signalfd_ctx *ctx = file->private_data;
206 : struct signalfd_siginfo __user *siginfo;
207 0 : int nonblock = file->f_flags & O_NONBLOCK;
208 0 : ssize_t ret, total = 0;
209 : kernel_siginfo_t info;
210 :
211 0 : count /= sizeof(struct signalfd_siginfo);
212 0 : if (!count)
213 : return -EINVAL;
214 :
215 : siginfo = (struct signalfd_siginfo __user *) buf;
216 : do {
217 0 : ret = signalfd_dequeue(ctx, &info, nonblock);
218 0 : if (unlikely(ret <= 0))
219 : break;
220 0 : ret = signalfd_copyinfo(siginfo, &info);
221 0 : if (ret < 0)
222 : break;
223 0 : siginfo++;
224 0 : total += ret;
225 0 : nonblock = 1;
226 0 : } while (--count);
227 :
228 0 : return total ? total: ret;
229 : }
230 :
231 : #ifdef CONFIG_PROC_FS
232 0 : static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
233 : {
234 0 : struct signalfd_ctx *ctx = f->private_data;
235 : sigset_t sigmask;
236 :
237 0 : sigmask = ctx->sigmask;
238 0 : signotset(&sigmask);
239 0 : render_sigset_t(m, "sigmask:\t", &sigmask);
240 0 : }
241 : #endif
242 :
243 : static 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 :
253 0 : static 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 0 : if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
262 : return -EINVAL;
263 :
264 0 : sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
265 0 : signotset(mask);
266 :
267 0 : if (ufd == -1) {
268 0 : ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
269 0 : if (!ctx)
270 : return -ENOMEM;
271 :
272 0 : 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 0 : ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
279 0 : O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
280 0 : if (ufd < 0)
281 0 : kfree(ctx);
282 : } else {
283 0 : struct fd f = fdget(ufd);
284 0 : if (!f.file)
285 0 : return -EBADF;
286 0 : ctx = f.file->private_data;
287 0 : if (f.file->f_op != &signalfd_fops) {
288 0 : fdput(f);
289 : return -EINVAL;
290 : }
291 0 : spin_lock_irq(¤t->sighand->siglock);
292 0 : ctx->sigmask = *mask;
293 0 : spin_unlock_irq(¤t->sighand->siglock);
294 :
295 0 : wake_up(¤t->sighand->signalfd_wqh);
296 0 : fdput(f);
297 : }
298 :
299 : return ufd;
300 : }
301 :
302 0 : SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
303 : size_t, sizemask, int, flags)
304 : {
305 : sigset_t mask;
306 :
307 0 : if (sizemask != sizeof(sigset_t))
308 : return -EINVAL;
309 0 : if (copy_from_user(&mask, user_mask, sizeof(mask)))
310 : return -EFAULT;
311 0 : return do_signalfd4(ufd, &mask, flags);
312 : }
313 :
314 0 : SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
315 : size_t, sizemask)
316 : {
317 : sigset_t mask;
318 :
319 0 : if (sizemask != sizeof(sigset_t))
320 : return -EINVAL;
321 0 : if (copy_from_user(&mask, user_mask, sizeof(mask)))
322 : return -EFAULT;
323 0 : return do_signalfd4(ufd, &mask, 0);
324 : }
325 :
326 : #ifdef CONFIG_COMPAT
327 : static 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 :
340 : COMPAT_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 :
348 : COMPAT_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
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