fs/signalfd.c

   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, &current->sighand->signalfd_wqh, wait);
  57
  58         spin_lock_irq(&current->sighand->siglock);
  59         if (next_signal(&current->pending, &ctx->sigmask) ||
  60             next_signal(&current->signal->shared_pending,
  61                         &ctx->sigmask))
  62                 events |= EPOLLIN;
  63         spin_unlock_irq(&current->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(&current->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(&current->sighand->siglock);
 172                 return ret;
 173         }
 174
 175         add_wait_queue(&current->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(&current->sighand->siglock);
 186                 schedule();
 187                 spin_lock_irq(&current->sighand->siglock);
 188         }
 189         spin_unlock_irq(&current->sighand->siglock);
 190
 191         remove_wait_queue(&current->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(&current->sighand->siglock);
 292                 ctx->sigmask = *mask;
 293                 spin_unlock_irq(&current->sighand->siglock);
 294
 295                 wake_up(&current->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