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TOMOYO Linux Cross Reference
Linux/fs/signalfd.c

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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, EPOLLHUP | 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 __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, &current->sighand->signalfd_wqh, wait);
 67 
 68         spin_lock_irq(&current->sighand->siglock);
 69         if (next_signal(&current->pending, &ctx->sigmask) ||
 70             next_signal(&current->signal->shared_pending,
 71                         &ctx->sigmask))
 72                 events |= EPOLLIN;
 73         spin_unlock_irq(&current->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_AO)
127                         err |= __put_user((short) kinfo->si_addr_lsb,
128                                           &uinfo->ssi_addr_lsb);
129 #endif
130 #ifdef BUS_MCEERR_AR
131                 /*
132                  * Other callers might not initialize the si_lsb field,
133                  * so check explicitly for the right codes here.
134                  */
135                 if (kinfo->si_signo == SIGBUS &&
136                     kinfo->si_code == BUS_MCEERR_AR)
137                         err |= __put_user((short) kinfo->si_addr_lsb,
138                                           &uinfo->ssi_addr_lsb);
139 #endif
140                 break;
141         case SIL_CHLD:
142                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
143                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
144                 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
145                 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
146                 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
147                 break;
148         case SIL_RT:
149         default:
150                 /*
151                  * This case catches also the signals queued by sigqueue().
152                  */
153                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
154                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
155                 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
156                 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
157                 break;
158         }
159 
160         return err ? -EFAULT: sizeof(*uinfo);
161 }
162 
163 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
164                                 int nonblock)
165 {
166         ssize_t ret;
167         DECLARE_WAITQUEUE(wait, current);
168 
169         spin_lock_irq(&current->sighand->siglock);
170         ret = dequeue_signal(current, &ctx->sigmask, info);
171         switch (ret) {
172         case 0:
173                 if (!nonblock)
174                         break;
175                 ret = -EAGAIN;
176         default:
177                 spin_unlock_irq(&current->sighand->siglock);
178                 return ret;
179         }
180 
181         add_wait_queue(&current->sighand->signalfd_wqh, &wait);
182         for (;;) {
183                 set_current_state(TASK_INTERRUPTIBLE);
184                 ret = dequeue_signal(current, &ctx->sigmask, info);
185                 if (ret != 0)
186                         break;
187                 if (signal_pending(current)) {
188                         ret = -ERESTARTSYS;
189                         break;
190                 }
191                 spin_unlock_irq(&current->sighand->siglock);
192                 schedule();
193                 spin_lock_irq(&current->sighand->siglock);
194         }
195         spin_unlock_irq(&current->sighand->siglock);
196 
197         remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
198         __set_current_state(TASK_RUNNING);
199 
200         return ret;
201 }
202 
203 /*
204  * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
205  * error code. The "count" parameter must be at least the size of a
206  * "struct signalfd_siginfo".
207  */
208 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
209                              loff_t *ppos)
210 {
211         struct signalfd_ctx *ctx = file->private_data;
212         struct signalfd_siginfo __user *siginfo;
213         int nonblock = file->f_flags & O_NONBLOCK;
214         ssize_t ret, total = 0;
215         siginfo_t info;
216 
217         count /= sizeof(struct signalfd_siginfo);
218         if (!count)
219                 return -EINVAL;
220 
221         siginfo = (struct signalfd_siginfo __user *) buf;
222         do {
223                 ret = signalfd_dequeue(ctx, &info, nonblock);
224                 if (unlikely(ret <= 0))
225                         break;
226                 ret = signalfd_copyinfo(siginfo, &info);
227                 if (ret < 0)
228                         break;
229                 siginfo++;
230                 total += ret;
231                 nonblock = 1;
232         } while (--count);
233 
234         return total ? total: ret;
235 }
236 
237 #ifdef CONFIG_PROC_FS
238 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
239 {
240         struct signalfd_ctx *ctx = f->private_data;
241         sigset_t sigmask;
242 
243         sigmask = ctx->sigmask;
244         signotset(&sigmask);
245         render_sigset_t(m, "sigmask:\t", &sigmask);
246 }
247 #endif
248 
249 static const struct file_operations signalfd_fops = {
250 #ifdef CONFIG_PROC_FS
251         .show_fdinfo    = signalfd_show_fdinfo,
252 #endif
253         .release        = signalfd_release,
254         .poll           = signalfd_poll,
255         .read           = signalfd_read,
256         .llseek         = noop_llseek,
257 };
258 
259 static int do_signalfd4(int ufd, sigset_t __user *user_mask, size_t sizemask,
260                         int flags)
261 {
262         sigset_t sigmask;
263         struct signalfd_ctx *ctx;
264 
265         /* Check the SFD_* constants for consistency.  */
266         BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
267         BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
268 
269         if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
270                 return -EINVAL;
271 
272         if (sizemask != sizeof(sigset_t) ||
273             copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
274                 return -EINVAL;
275         sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
276         signotset(&sigmask);
277 
278         if (ufd == -1) {
279                 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
280                 if (!ctx)
281                         return -ENOMEM;
282 
283                 ctx->sigmask = sigmask;
284 
285                 /*
286                  * When we call this, the initialization must be complete, since
287                  * anon_inode_getfd() will install the fd.
288                  */
289                 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
290                                        O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
291                 if (ufd < 0)
292                         kfree(ctx);
293         } else {
294                 struct fd f = fdget(ufd);
295                 if (!f.file)
296                         return -EBADF;
297                 ctx = f.file->private_data;
298                 if (f.file->f_op != &signalfd_fops) {
299                         fdput(f);
300                         return -EINVAL;
301                 }
302                 spin_lock_irq(&current->sighand->siglock);
303                 ctx->sigmask = sigmask;
304                 spin_unlock_irq(&current->sighand->siglock);
305 
306                 wake_up(&current->sighand->signalfd_wqh);
307                 fdput(f);
308         }
309 
310         return ufd;
311 }
312 
313 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
314                 size_t, sizemask, int, flags)
315 {
316         return do_signalfd4(ufd, user_mask, sizemask, flags);
317 }
318 
319 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
320                 size_t, sizemask)
321 {
322         return do_signalfd4(ufd, user_mask, sizemask, 0);
323 }
324 
325 #ifdef CONFIG_COMPAT
326 static long do_compat_signalfd4(int ufd,
327                         const compat_sigset_t __user *sigmask,
328                         compat_size_t sigsetsize, int flags)
329 {
330         sigset_t tmp;
331         sigset_t __user *ksigmask;
332 
333         if (sigsetsize != sizeof(compat_sigset_t))
334                 return -EINVAL;
335         if (get_compat_sigset(&tmp, sigmask))
336                 return -EFAULT;
337         ksigmask = compat_alloc_user_space(sizeof(sigset_t));
338         if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t)))
339                 return -EFAULT;
340 
341         return do_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags);
342 }
343 
344 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
345                      const compat_sigset_t __user *, sigmask,
346                      compat_size_t, sigsetsize,
347                      int, flags)
348 {
349         return do_compat_signalfd4(ufd, sigmask, sigsetsize, flags);
350 }
351 
352 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
353                      const compat_sigset_t __user *,sigmask,
354                      compat_size_t, sigsetsize)
355 {
356         return do_compat_signalfd4(ufd, sigmask, sigsetsize, 0);
357 }
358 #endif
359 

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