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
signalfd_cleanup(struct sighand_struct * sighand)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, EPOLLHUP | POLLFREE);
49 }
50
51 struct signalfd_ctx {
52 sigset_t sigmask;
53 };
54
signalfd_release(struct inode * inode,struct file * file)55 static int signalfd_release(struct inode *inode, struct file *file)
56 {
57 kfree(file->private_data);
58 return 0;
59 }
60
signalfd_poll(struct file * file,poll_table * wait)61 static __poll_t signalfd_poll(struct file *file, poll_table *wait)
62 {
63 struct signalfd_ctx *ctx = file->private_data;
64 __poll_t 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 |= EPOLLIN;
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 */
signalfd_copyinfo(struct signalfd_siginfo __user * uinfo,kernel_siginfo_t const * kinfo)81 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
82 kernel_siginfo_t const *kinfo)
83 {
84 struct signalfd_siginfo new;
85
86 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
87
88 /*
89 * Unused members should be zero ...
90 */
91 memset(&new, 0, sizeof(new));
92
93 /*
94 * If you change siginfo_t structure, please be sure
95 * this code is fixed accordingly.
96 */
97 new.ssi_signo = kinfo->si_signo;
98 new.ssi_errno = kinfo->si_errno;
99 new.ssi_code = kinfo->si_code;
100 switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) {
101 case SIL_KILL:
102 new.ssi_pid = kinfo->si_pid;
103 new.ssi_uid = kinfo->si_uid;
104 break;
105 case SIL_TIMER:
106 new.ssi_tid = kinfo->si_tid;
107 new.ssi_overrun = kinfo->si_overrun;
108 new.ssi_ptr = (long) kinfo->si_ptr;
109 new.ssi_int = kinfo->si_int;
110 break;
111 case SIL_POLL:
112 new.ssi_band = kinfo->si_band;
113 new.ssi_fd = kinfo->si_fd;
114 break;
115 case SIL_FAULT_BNDERR:
116 case SIL_FAULT_PKUERR:
117 /*
118 * Fall through to the SIL_FAULT case. Both SIL_FAULT_BNDERR
119 * and SIL_FAULT_PKUERR are only generated by faults that
120 * deliver them synchronously to userspace. In case someone
121 * injects one of these signals and signalfd catches it treat
122 * it as SIL_FAULT.
123 */
124 case SIL_FAULT:
125 new.ssi_addr = (long) kinfo->si_addr;
126 #ifdef __ARCH_SI_TRAPNO
127 new.ssi_trapno = kinfo->si_trapno;
128 #endif
129 break;
130 case SIL_FAULT_MCEERR:
131 new.ssi_addr = (long) kinfo->si_addr;
132 #ifdef __ARCH_SI_TRAPNO
133 new.ssi_trapno = kinfo->si_trapno;
134 #endif
135 new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
136 break;
137 case SIL_PERF_EVENT:
138 new.ssi_addr = (long) kinfo->si_addr;
139 new.ssi_perf = kinfo->si_perf;
140 break;
141 case SIL_CHLD:
142 new.ssi_pid = kinfo->si_pid;
143 new.ssi_uid = kinfo->si_uid;
144 new.ssi_status = kinfo->si_status;
145 new.ssi_utime = kinfo->si_utime;
146 new.ssi_stime = kinfo->si_stime;
147 break;
148 case SIL_RT:
149 /*
150 * This case catches also the signals queued by sigqueue().
151 */
152 new.ssi_pid = kinfo->si_pid;
153 new.ssi_uid = kinfo->si_uid;
154 new.ssi_ptr = (long) kinfo->si_ptr;
155 new.ssi_int = kinfo->si_int;
156 break;
157 case SIL_SYS:
158 new.ssi_call_addr = (long) kinfo->si_call_addr;
159 new.ssi_syscall = kinfo->si_syscall;
160 new.ssi_arch = kinfo->si_arch;
161 break;
162 }
163
164 if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
165 return -EFAULT;
166
167 return sizeof(*uinfo);
168 }
169
signalfd_dequeue(struct signalfd_ctx * ctx,kernel_siginfo_t * info,int nonblock)170 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
171 int nonblock)
172 {
173 ssize_t ret;
174 DECLARE_WAITQUEUE(wait, current);
175
176 spin_lock_irq(¤t->sighand->siglock);
177 ret = dequeue_signal(current, &ctx->sigmask, info);
178 switch (ret) {
179 case 0:
180 if (!nonblock)
181 break;
182 ret = -EAGAIN;
183 fallthrough;
184 default:
185 spin_unlock_irq(¤t->sighand->siglock);
186 return ret;
187 }
188
189 add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
190 for (;;) {
191 set_current_state(TASK_INTERRUPTIBLE);
192 ret = dequeue_signal(current, &ctx->sigmask, info);
193 if (ret != 0)
194 break;
195 if (signal_pending(current)) {
196 ret = -ERESTARTSYS;
197 break;
198 }
199 spin_unlock_irq(¤t->sighand->siglock);
200 schedule();
201 spin_lock_irq(¤t->sighand->siglock);
202 }
203 spin_unlock_irq(¤t->sighand->siglock);
204
205 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
206 __set_current_state(TASK_RUNNING);
207
208 return ret;
209 }
210
211 /*
212 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
213 * error code. The "count" parameter must be at least the size of a
214 * "struct signalfd_siginfo".
215 */
signalfd_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)216 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
217 loff_t *ppos)
218 {
219 struct signalfd_ctx *ctx = file->private_data;
220 struct signalfd_siginfo __user *siginfo;
221 int nonblock = file->f_flags & O_NONBLOCK;
222 ssize_t ret, total = 0;
223 kernel_siginfo_t info;
224
225 count /= sizeof(struct signalfd_siginfo);
226 if (!count)
227 return -EINVAL;
228
229 siginfo = (struct signalfd_siginfo __user *) buf;
230 do {
231 ret = signalfd_dequeue(ctx, &info, nonblock);
232 if (unlikely(ret <= 0))
233 break;
234 ret = signalfd_copyinfo(siginfo, &info);
235 if (ret < 0)
236 break;
237 siginfo++;
238 total += ret;
239 nonblock = 1;
240 } while (--count);
241
242 return total ? total: ret;
243 }
244
245 #ifdef CONFIG_PROC_FS
signalfd_show_fdinfo(struct seq_file * m,struct file * f)246 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
247 {
248 struct signalfd_ctx *ctx = f->private_data;
249 sigset_t sigmask;
250
251 sigmask = ctx->sigmask;
252 signotset(&sigmask);
253 render_sigset_t(m, "sigmask:\t", &sigmask);
254 }
255 #endif
256
257 static const struct file_operations signalfd_fops = {
258 #ifdef CONFIG_PROC_FS
259 .show_fdinfo = signalfd_show_fdinfo,
260 #endif
261 .release = signalfd_release,
262 .poll = signalfd_poll,
263 .read = signalfd_read,
264 .llseek = noop_llseek,
265 };
266
do_signalfd4(int ufd,sigset_t * mask,int flags)267 static int do_signalfd4(int ufd, sigset_t *mask, int flags)
268 {
269 struct signalfd_ctx *ctx;
270
271 /* Check the SFD_* constants for consistency. */
272 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
273 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
274
275 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
276 return -EINVAL;
277
278 sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
279 signotset(mask);
280
281 if (ufd == -1) {
282 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
283 if (!ctx)
284 return -ENOMEM;
285
286 ctx->sigmask = *mask;
287
288 /*
289 * When we call this, the initialization must be complete, since
290 * anon_inode_getfd() will install the fd.
291 */
292 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
293 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
294 if (ufd < 0)
295 kfree(ctx);
296 } else {
297 struct fd f = fdget(ufd);
298 if (!f.file)
299 return -EBADF;
300 ctx = f.file->private_data;
301 if (f.file->f_op != &signalfd_fops) {
302 fdput(f);
303 return -EINVAL;
304 }
305 spin_lock_irq(¤t->sighand->siglock);
306 ctx->sigmask = *mask;
307 spin_unlock_irq(¤t->sighand->siglock);
308
309 wake_up(¤t->sighand->signalfd_wqh);
310 fdput(f);
311 }
312
313 return ufd;
314 }
315
SYSCALL_DEFINE4(signalfd4,int,ufd,sigset_t __user *,user_mask,size_t,sizemask,int,flags)316 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
317 size_t, sizemask, int, flags)
318 {
319 sigset_t mask;
320
321 if (sizemask != sizeof(sigset_t))
322 return -EINVAL;
323 if (copy_from_user(&mask, user_mask, sizeof(mask)))
324 return -EFAULT;
325 return do_signalfd4(ufd, &mask, flags);
326 }
327
SYSCALL_DEFINE3(signalfd,int,ufd,sigset_t __user *,user_mask,size_t,sizemask)328 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
329 size_t, sizemask)
330 {
331 sigset_t mask;
332
333 if (sizemask != sizeof(sigset_t))
334 return -EINVAL;
335 if (copy_from_user(&mask, user_mask, sizeof(mask)))
336 return -EFAULT;
337 return do_signalfd4(ufd, &mask, 0);
338 }
339
340 #ifdef CONFIG_COMPAT
do_compat_signalfd4(int ufd,const compat_sigset_t __user * user_mask,compat_size_t sigsetsize,int flags)341 static long do_compat_signalfd4(int ufd,
342 const compat_sigset_t __user *user_mask,
343 compat_size_t sigsetsize, int flags)
344 {
345 sigset_t mask;
346
347 if (sigsetsize != sizeof(compat_sigset_t))
348 return -EINVAL;
349 if (get_compat_sigset(&mask, user_mask))
350 return -EFAULT;
351 return do_signalfd4(ufd, &mask, flags);
352 }
353
COMPAT_SYSCALL_DEFINE4(signalfd4,int,ufd,const compat_sigset_t __user *,user_mask,compat_size_t,sigsetsize,int,flags)354 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
355 const compat_sigset_t __user *, user_mask,
356 compat_size_t, sigsetsize,
357 int, flags)
358 {
359 return do_compat_signalfd4(ufd, user_mask, sigsetsize, flags);
360 }
361
COMPAT_SYSCALL_DEFINE3(signalfd,int,ufd,const compat_sigset_t __user *,user_mask,compat_size_t,sigsetsize)362 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
363 const compat_sigset_t __user *, user_mask,
364 compat_size_t, sigsetsize)
365 {
366 return do_compat_signalfd4(ufd, user_mask, sigsetsize, 0);
367 }
368 #endif
369