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(&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(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(file, ¤t->sighand->signalfd_wqh, wait); 57 58 spin_lock_irq(¤t->sighand->siglock); 59 if (next_signal(¤t->pending, &ctx->sigmask) || 60 next_signal(¤t->signal->shared_pending, 61 &ctx->sigmask)) 62 events |= EPOLLIN; 63 spin_unlock_irq(¤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(kinfo->si_signo, 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(uinfo, &new, 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(¤t->sighand->siglock); 163 ret = dequeue_signal(current, &ctx->sigmask, info, &type); 164 switch (ret) { 165 case 0: 166 if (!nonblock) 167 break; 168 ret = -EAGAIN; 169 fallthrough; 170 default: 171 spin_unlock_irq(¤t->sighand->siglock); 172 return ret; 173 } 174 175 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 176 for (;;) { 177 set_current_state(TASK_INTERRUPTIBLE); 178 ret = dequeue_signal(current, &ctx->sigmask, info, &type); 179 if (ret != 0) 180 break; 181 if (signal_pending(current)) { 182 ret = -ERESTARTSYS; 183 break; 184 } 185 spin_unlock_irq(¤t->sighand->siglock); 186 schedule(); 187 spin_lock_irq(¤t->sighand->siglock); 188 } 189 spin_unlock_irq(¤t->sighand->siglock); 190 191 remove_wait_queue(¤t->sighand->signalfd_wqh, &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, nonblock); 218 if (unlikely(ret <= 0)) 219 break; 220 ret = signalfd_copyinfo(siginfo, &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(&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(mask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 265 signotset(mask); 266 267 if (ufd == -1) { 268 ctx = kmalloc(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("[signalfd]", &signalfd_fops, ctx, 279 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 280 if (ufd < 0) 281 kfree(ctx); 282 } else { 283 struct fd f = fdget(ufd); 284 if (!f.file) 285 return -EBADF; 286 ctx = f.file->private_data; 287 if (f.file->f_op != &signalfd_fops) { 288 fdput(f); 289 return -EINVAL; 290 } 291 spin_lock_irq(¤t->sighand->siglock); 292 ctx->sigmask = *mask; 293 spin_unlock_irq(¤t->sighand->siglock); 294 295 wake_up(¤t->sighand->signalfd_wqh); 296 fdput(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(&mask, user_mask, sizeof(mask))) 310 return -EFAULT; 311 return do_signalfd4(ufd, &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(&mask, user_mask, sizeof(mask))) 322 return -EFAULT; 323 return do_signalfd4(ufd, &mask, 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(&mask, user_mask)) 336 return -EFAULT; 337 return do_signalfd4(ufd, &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, 0); 353 } 354 #endif 355