1 /*
2 * fs/signalfd.c
3 *
4 * Copyright (C) 2003 Linus Torvalds
5 *
6 * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
7 * Changed ->read() to return a siginfo strcture instead of signal number.
8 * Fixed locking in ->poll().
9 * Added sighand-detach notification.
10 * Added fd re-use in sys_signalfd() syscall.
11 * Now using anonymous inode source.
12 * Thanks to Oleg Nesterov for useful code review and suggestions.
13 * More comments and suggestions from Arnd Bergmann.
14 * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
15 * Retrieve multiple signals with one read() call
16 * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
17 * Attach to the sighand only during read() and poll().
18 */
19
20 #include <linux/file.h>
21 #include <linux/poll.h>
22 #include <linux/init.h>
23 #include <linux/fs.h>
24 #include <linux/sched.h>
25 #include <linux/slab.h>
26 #include <linux/kernel.h>
27 #include <linux/signal.h>
28 #include <linux/list.h>
29 #include <linux/anon_inodes.h>
30 #include <linux/signalfd.h>
31 #include <linux/syscalls.h>
32 #include <linux/proc_fs.h>
33 #include <linux/compat.h>
34
signalfd_cleanup(struct sighand_struct * sighand)35 void signalfd_cleanup(struct sighand_struct *sighand)
36 {
37 wake_up_pollfree(&sighand->signalfd_wqh);
38 }
39
40 struct signalfd_ctx {
41 sigset_t sigmask;
42 };
43
signalfd_release(struct inode * inode,struct file * file)44 static int signalfd_release(struct inode *inode, struct file *file)
45 {
46 kfree(file->private_data);
47 return 0;
48 }
49
signalfd_poll(struct file * file,poll_table * wait)50 static unsigned int signalfd_poll(struct file *file, poll_table *wait)
51 {
52 struct signalfd_ctx *ctx = file->private_data;
53 unsigned int events = 0;
54
55 poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
56
57 spin_lock_irq(¤t->sighand->siglock);
58 if (next_signal(¤t->pending, &ctx->sigmask) ||
59 next_signal(¤t->signal->shared_pending,
60 &ctx->sigmask))
61 events |= POLLIN;
62 spin_unlock_irq(¤t->sighand->siglock);
63
64 return events;
65 }
66
67 /*
68 * Copied from copy_siginfo_to_user() in kernel/signal.c
69 */
signalfd_copyinfo(struct signalfd_siginfo __user * uinfo,siginfo_t const * kinfo)70 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
71 siginfo_t const *kinfo)
72 {
73 long err;
74
75 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
76
77 /*
78 * Unused members should be zero ...
79 */
80 err = __clear_user(uinfo, sizeof(*uinfo));
81
82 /*
83 * If you change siginfo_t structure, please be sure
84 * this code is fixed accordingly.
85 */
86 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
87 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
88 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
89 switch (kinfo->si_code & __SI_MASK) {
90 case __SI_KILL:
91 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
92 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
93 break;
94 case __SI_TIMER:
95 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
96 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
97 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
98 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
99 break;
100 case __SI_POLL:
101 err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
102 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
103 break;
104 case __SI_FAULT:
105 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
106 #ifdef __ARCH_SI_TRAPNO
107 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
108 #endif
109 #ifdef BUS_MCEERR_AO
110 /*
111 * Other callers might not initialize the si_lsb field,
112 * so check explicitly for the right codes here.
113 */
114 if (kinfo->si_signo == SIGBUS &&
115 (kinfo->si_code == BUS_MCEERR_AR ||
116 kinfo->si_code == BUS_MCEERR_AO))
117 err |= __put_user((short) kinfo->si_addr_lsb,
118 &uinfo->ssi_addr_lsb);
119 #endif
120 break;
121 case __SI_CHLD:
122 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
123 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
124 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
125 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
126 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
127 break;
128 case __SI_RT: /* This is not generated by the kernel as of now. */
129 case __SI_MESGQ: /* But this is */
130 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
131 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
132 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
133 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
134 break;
135 default:
136 /*
137 * This case catches also the signals queued by sigqueue().
138 */
139 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
140 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
141 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
142 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
143 break;
144 }
145
146 return err ? -EFAULT: sizeof(*uinfo);
147 }
148
signalfd_dequeue(struct signalfd_ctx * ctx,siginfo_t * info,int nonblock)149 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
150 int nonblock)
151 {
152 ssize_t ret;
153 DECLARE_WAITQUEUE(wait, current);
154
155 spin_lock_irq(¤t->sighand->siglock);
156 ret = dequeue_signal(current, &ctx->sigmask, info);
157 switch (ret) {
158 case 0:
159 if (!nonblock)
160 break;
161 ret = -EAGAIN;
162 default:
163 spin_unlock_irq(¤t->sighand->siglock);
164 return ret;
165 }
166
167 add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
168 for (;;) {
169 set_current_state(TASK_INTERRUPTIBLE);
170 ret = dequeue_signal(current, &ctx->sigmask, info);
171 if (ret != 0)
172 break;
173 if (signal_pending(current)) {
174 ret = -ERESTARTSYS;
175 break;
176 }
177 spin_unlock_irq(¤t->sighand->siglock);
178 schedule();
179 spin_lock_irq(¤t->sighand->siglock);
180 }
181 spin_unlock_irq(¤t->sighand->siglock);
182
183 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
184 __set_current_state(TASK_RUNNING);
185
186 return ret;
187 }
188
189 /*
190 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
191 * error code. The "count" parameter must be at least the size of a
192 * "struct signalfd_siginfo".
193 */
signalfd_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)194 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
195 loff_t *ppos)
196 {
197 struct signalfd_ctx *ctx = file->private_data;
198 struct signalfd_siginfo __user *siginfo;
199 int nonblock = file->f_flags & O_NONBLOCK;
200 ssize_t ret, total = 0;
201 siginfo_t info;
202
203 count /= sizeof(struct signalfd_siginfo);
204 if (!count)
205 return -EINVAL;
206
207 siginfo = (struct signalfd_siginfo __user *) buf;
208 do {
209 ret = signalfd_dequeue(ctx, &info, nonblock);
210 if (unlikely(ret <= 0))
211 break;
212 ret = signalfd_copyinfo(siginfo, &info);
213 if (ret < 0)
214 break;
215 siginfo++;
216 total += ret;
217 nonblock = 1;
218 } while (--count);
219
220 return total ? total: ret;
221 }
222
223 #ifdef CONFIG_PROC_FS
signalfd_show_fdinfo(struct seq_file * m,struct file * f)224 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
225 {
226 struct signalfd_ctx *ctx = f->private_data;
227 sigset_t sigmask;
228
229 sigmask = ctx->sigmask;
230 signotset(&sigmask);
231 render_sigset_t(m, "sigmask:\t", &sigmask);
232 }
233 #endif
234
235 static const struct file_operations signalfd_fops = {
236 #ifdef CONFIG_PROC_FS
237 .show_fdinfo = signalfd_show_fdinfo,
238 #endif
239 .release = signalfd_release,
240 .poll = signalfd_poll,
241 .read = signalfd_read,
242 .llseek = noop_llseek,
243 };
244
SYSCALL_DEFINE4(signalfd4,int,ufd,sigset_t __user *,user_mask,size_t,sizemask,int,flags)245 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
246 size_t, sizemask, int, flags)
247 {
248 sigset_t sigmask;
249 struct signalfd_ctx *ctx;
250
251 /* Check the SFD_* constants for consistency. */
252 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
253 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
254
255 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
256 return -EINVAL;
257
258 if (sizemask != sizeof(sigset_t) ||
259 copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
260 return -EINVAL;
261 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
262 signotset(&sigmask);
263
264 if (ufd == -1) {
265 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
266 if (!ctx)
267 return -ENOMEM;
268
269 ctx->sigmask = sigmask;
270
271 /*
272 * When we call this, the initialization must be complete, since
273 * anon_inode_getfd() will install the fd.
274 */
275 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
276 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
277 if (ufd < 0)
278 kfree(ctx);
279 } else {
280 struct fd f = fdget(ufd);
281 if (!f.file)
282 return -EBADF;
283 ctx = f.file->private_data;
284 if (f.file->f_op != &signalfd_fops) {
285 fdput(f);
286 return -EINVAL;
287 }
288 spin_lock_irq(¤t->sighand->siglock);
289 ctx->sigmask = sigmask;
290 spin_unlock_irq(¤t->sighand->siglock);
291
292 wake_up(¤t->sighand->signalfd_wqh);
293 fdput(f);
294 }
295
296 return ufd;
297 }
298
SYSCALL_DEFINE3(signalfd,int,ufd,sigset_t __user *,user_mask,size_t,sizemask)299 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
300 size_t, sizemask)
301 {
302 return sys_signalfd4(ufd, user_mask, sizemask, 0);
303 }
304
305 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(signalfd4,int,ufd,const compat_sigset_t __user *,sigmask,compat_size_t,sigsetsize,int,flags)306 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
307 const compat_sigset_t __user *,sigmask,
308 compat_size_t, sigsetsize,
309 int, flags)
310 {
311 compat_sigset_t ss32;
312 sigset_t tmp;
313 sigset_t __user *ksigmask;
314
315 if (sigsetsize != sizeof(compat_sigset_t))
316 return -EINVAL;
317 if (copy_from_user(&ss32, sigmask, sizeof(ss32)))
318 return -EFAULT;
319 sigset_from_compat(&tmp, &ss32);
320 ksigmask = compat_alloc_user_space(sizeof(sigset_t));
321 if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t)))
322 return -EFAULT;
323
324 return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags);
325 }
326
COMPAT_SYSCALL_DEFINE3(signalfd,int,ufd,const compat_sigset_t __user *,sigmask,compat_size_t,sigsetsize)327 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
328 const compat_sigset_t __user *,sigmask,
329 compat_size_t, sigsetsize)
330 {
331 return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0);
332 }
333 #endif
334