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, ¤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 */ 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_AR || 127 kinfo->si_code == BUS_MCEERR_AO)) 128 err |= __put_user((short) kinfo->si_addr_lsb, 129 &uinfo->ssi_addr_lsb); 130 #endif 131 break; 132 case SIL_CHLD: 133 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 134 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 135 err |= __put_user(kinfo->si_status, &uinfo->ssi_status); 136 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); 137 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); 138 break; 139 case SIL_RT: 140 default: 141 /* 142 * This case catches also the signals queued by sigqueue(). 143 */ 144 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 145 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 146 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 147 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 148 break; 149 } 150 151 return err ? -EFAULT: sizeof(*uinfo); 152 } 153 154 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 155 int nonblock) 156 { 157 ssize_t ret; 158 DECLARE_WAITQUEUE(wait, current); 159 160 spin_lock_irq(¤t->sighand->siglock); 161 ret = dequeue_signal(current, &ctx->sigmask, info); 162 switch (ret) { 163 case 0: 164 if (!nonblock) 165 break; 166 ret = -EAGAIN; 167 default: 168 spin_unlock_irq(¤t->sighand->siglock); 169 return ret; 170 } 171 172 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 173 for (;;) { 174 set_current_state(TASK_INTERRUPTIBLE); 175 ret = dequeue_signal(current, &ctx->sigmask, info); 176 if (ret != 0) 177 break; 178 if (signal_pending(current)) { 179 ret = -ERESTARTSYS; 180 break; 181 } 182 spin_unlock_irq(¤t->sighand->siglock); 183 schedule(); 184 spin_lock_irq(¤t->sighand->siglock); 185 } 186 spin_unlock_irq(¤t->sighand->siglock); 187 188 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 189 __set_current_state(TASK_RUNNING); 190 191 return ret; 192 } 193 194 /* 195 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 196 * error code. The "count" parameter must be at least the size of a 197 * "struct signalfd_siginfo". 198 */ 199 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 200 loff_t *ppos) 201 { 202 struct signalfd_ctx *ctx = file->private_data; 203 struct signalfd_siginfo __user *siginfo; 204 int nonblock = file->f_flags & O_NONBLOCK; 205 ssize_t ret, total = 0; 206 siginfo_t info; 207 208 count /= sizeof(struct signalfd_siginfo); 209 if (!count) 210 return -EINVAL; 211 212 siginfo = (struct signalfd_siginfo __user *) buf; 213 do { 214 ret = signalfd_dequeue(ctx, &info, nonblock); 215 if (unlikely(ret <= 0)) 216 break; 217 ret = signalfd_copyinfo(siginfo, &info); 218 if (ret < 0) 219 break; 220 siginfo++; 221 total += ret; 222 nonblock = 1; 223 } while (--count); 224 225 return total ? total: ret; 226 } 227 228 #ifdef CONFIG_PROC_FS 229 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) 230 { 231 struct signalfd_ctx *ctx = f->private_data; 232 sigset_t sigmask; 233 234 sigmask = ctx->sigmask; 235 signotset(&sigmask); 236 render_sigset_t(m, "sigmask:\t", &sigmask); 237 } 238 #endif 239 240 static const struct file_operations signalfd_fops = { 241 #ifdef CONFIG_PROC_FS 242 .show_fdinfo = signalfd_show_fdinfo, 243 #endif 244 .release = signalfd_release, 245 .poll = signalfd_poll, 246 .read = signalfd_read, 247 .llseek = noop_llseek, 248 }; 249 250 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 251 size_t, sizemask, int, flags) 252 { 253 sigset_t sigmask; 254 struct signalfd_ctx *ctx; 255 256 /* Check the SFD_* constants for consistency. */ 257 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 258 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 259 260 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 261 return -EINVAL; 262 263 if (sizemask != sizeof(sigset_t) || 264 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 265 return -EINVAL; 266 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 267 signotset(&sigmask); 268 269 if (ufd == -1) { 270 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 271 if (!ctx) 272 return -ENOMEM; 273 274 ctx->sigmask = sigmask; 275 276 /* 277 * When we call this, the initialization must be complete, since 278 * anon_inode_getfd() will install the fd. 279 */ 280 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 281 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 282 if (ufd < 0) 283 kfree(ctx); 284 } else { 285 struct fd f = fdget(ufd); 286 if (!f.file) 287 return -EBADF; 288 ctx = f.file->private_data; 289 if (f.file->f_op != &signalfd_fops) { 290 fdput(f); 291 return -EINVAL; 292 } 293 spin_lock_irq(¤t->sighand->siglock); 294 ctx->sigmask = sigmask; 295 spin_unlock_irq(¤t->sighand->siglock); 296 297 wake_up(¤t->sighand->signalfd_wqh); 298 fdput(f); 299 } 300 301 return ufd; 302 } 303 304 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 305 size_t, sizemask) 306 { 307 return sys_signalfd4(ufd, user_mask, sizemask, 0); 308 } 309 310 #ifdef CONFIG_COMPAT 311 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, 312 const compat_sigset_t __user *,sigmask, 313 compat_size_t, sigsetsize, 314 int, flags) 315 { 316 sigset_t tmp; 317 sigset_t __user *ksigmask; 318 319 if (sigsetsize != sizeof(compat_sigset_t)) 320 return -EINVAL; 321 if (get_compat_sigset(&tmp, sigmask)) 322 return -EFAULT; 323 ksigmask = compat_alloc_user_space(sizeof(sigset_t)); 324 if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) 325 return -EFAULT; 326 327 return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); 328 } 329 330 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, 331 const compat_sigset_t __user *,sigmask, 332 compat_size_t, sigsetsize) 333 { 334 return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); 335 } 336 #endif 337