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 | wake_up_pollfree(wq_head: &sighand->signalfd_wqh); |
39 | } |
40 | |
41 | struct signalfd_ctx { |
42 | sigset_t sigmask; |
43 | }; |
44 | |
45 | static int signalfd_release(struct inode *inode, struct file *file) |
46 | { |
47 | kfree(objp: file->private_data); |
48 | return 0; |
49 | } |
50 | |
51 | static __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: ¤t->sighand->signalfd_wqh, p: wait); |
57 | |
58 | spin_lock_irq(lock: ¤t->sighand->siglock); |
59 | if (next_signal(pending: ¤t->pending, mask: &ctx->sigmask) || |
60 | next_signal(pending: ¤t->signal->shared_pending, |
61 | mask: &ctx->sigmask)) |
62 | events |= EPOLLIN; |
63 | spin_unlock_irq(lock: ¤t->sighand->siglock); |
64 | |
65 | return events; |
66 | } |
67 | |
68 | /* |
69 | * Copied from copy_siginfo_to_user() in kernel/signal.c |
70 | */ |
71 | 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 | 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 | |
155 | 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 | DECLARE_WAITQUEUE(wait, current); |
161 | |
162 | spin_lock_irq(lock: ¤t->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: ¤t->sighand->siglock); |
172 | return ret; |
173 | } |
174 | |
175 | add_wait_queue(wq_head: ¤t->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: ¤t->sighand->siglock); |
186 | schedule(); |
187 | spin_lock_irq(lock: ¤t->sighand->siglock); |
188 | } |
189 | spin_unlock_irq(lock: ¤t->sighand->siglock); |
190 | |
191 | remove_wait_queue(wq_head: ¤t->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 | */ |
202 | static 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 |
232 | static 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 | |
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 | 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 | 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: ¤t->sighand->siglock); |
292 | ctx->sigmask = *mask; |
293 | spin_unlock_irq(lock: ¤t->sighand->siglock); |
294 | |
295 | wake_up(¤t->sighand->signalfd_wqh); |
296 | fdput(fd: f); |
297 | } |
298 | |
299 | return ufd; |
300 | } |
301 | |
302 | SYSCALL_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 | |
314 | SYSCALL_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 |
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(set: &mask, compat: user_mask)) |
336 | return -EFAULT; |
337 | return do_signalfd4(ufd, mask: &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, flags: 0); |
353 | } |
354 | #endif |
355 | |