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- // SPDX-License-Identifier: GPL-2.0
- /*
- * fs/signalfd.c
- *
- * Copyright (C) 2003 Linus Torvalds
- *
- * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
- * Changed ->read() to return a siginfo strcture instead of signal number.
- * Fixed locking in ->poll().
- * Added sighand-detach notification.
- * Added fd re-use in sys_signalfd() syscall.
- * Now using anonymous inode source.
- * Thanks to Oleg Nesterov for useful code review and suggestions.
- * More comments and suggestions from Arnd Bergmann.
- * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
- * Retrieve multiple signals with one read() call
- * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
- * Attach to the sighand only during read() and poll().
- */
- #include <linux/file.h>
- #include <linux/poll.h>
- #include <linux/init.h>
- #include <linux/fs.h>
- #include <linux/sched.h>
- #include <linux/slab.h>
- #include <linux/kernel.h>
- #include <linux/signal.h>
- #include <linux/list.h>
- #include <linux/anon_inodes.h>
- #include <linux/signalfd.h>
- #include <linux/syscalls.h>
- #include <linux/proc_fs.h>
- #include <linux/compat.h>
- void signalfd_cleanup(struct sighand_struct *sighand)
- {
- wait_queue_head_t *wqh = &sighand->signalfd_wqh;
- /*
- * The lockless check can race with remove_wait_queue() in progress,
- * but in this case its caller should run under rcu_read_lock() and
- * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return.
- */
- if (likely(!waitqueue_active(wqh)))
- return;
- /* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */
- wake_up_poll(wqh, EPOLLHUP | POLLFREE);
- }
- struct signalfd_ctx {
- sigset_t sigmask;
- };
- static int signalfd_release(struct inode *inode, struct file *file)
- {
- kfree(file->private_data);
- return 0;
- }
- static __poll_t signalfd_poll(struct file *file, poll_table *wait)
- {
- struct signalfd_ctx *ctx = file->private_data;
- __poll_t events = 0;
- poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
- spin_lock_irq(¤t->sighand->siglock);
- if (next_signal(¤t->pending, &ctx->sigmask) ||
- next_signal(¤t->signal->shared_pending,
- &ctx->sigmask))
- events |= EPOLLIN;
- spin_unlock_irq(¤t->sighand->siglock);
- return events;
- }
- /*
- * Copied from copy_siginfo_to_user() in kernel/signal.c
- */
- static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
- siginfo_t const *kinfo)
- {
- struct signalfd_siginfo new;
- BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
- /*
- * Unused members should be zero ...
- */
- memset(&new, 0, sizeof(new));
- /*
- * If you change siginfo_t structure, please be sure
- * this code is fixed accordingly.
- */
- new.ssi_signo = kinfo->si_signo;
- new.ssi_errno = kinfo->si_errno;
- new.ssi_code = kinfo->si_code;
- switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) {
- case SIL_KILL:
- new.ssi_pid = kinfo->si_pid;
- new.ssi_uid = kinfo->si_uid;
- break;
- case SIL_TIMER:
- new.ssi_tid = kinfo->si_tid;
- new.ssi_overrun = kinfo->si_overrun;
- new.ssi_ptr = (long) kinfo->si_ptr;
- new.ssi_int = kinfo->si_int;
- break;
- case SIL_POLL:
- new.ssi_band = kinfo->si_band;
- new.ssi_fd = kinfo->si_fd;
- break;
- case SIL_FAULT_BNDERR:
- case SIL_FAULT_PKUERR:
- /*
- * Fall through to the SIL_FAULT case. Both SIL_FAULT_BNDERR
- * and SIL_FAULT_PKUERR are only generated by faults that
- * deliver them synchronously to userspace. In case someone
- * injects one of these signals and signalfd catches it treat
- * it as SIL_FAULT.
- */
- case SIL_FAULT:
- new.ssi_addr = (long) kinfo->si_addr;
- #ifdef __ARCH_SI_TRAPNO
- new.ssi_trapno = kinfo->si_trapno;
- #endif
- break;
- case SIL_FAULT_MCEERR:
- new.ssi_addr = (long) kinfo->si_addr;
- #ifdef __ARCH_SI_TRAPNO
- new.ssi_trapno = kinfo->si_trapno;
- #endif
- new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
- break;
- case SIL_CHLD:
- new.ssi_pid = kinfo->si_pid;
- new.ssi_uid = kinfo->si_uid;
- new.ssi_status = kinfo->si_status;
- new.ssi_utime = kinfo->si_utime;
- new.ssi_stime = kinfo->si_stime;
- break;
- case SIL_RT:
- /*
- * This case catches also the signals queued by sigqueue().
- */
- new.ssi_pid = kinfo->si_pid;
- new.ssi_uid = kinfo->si_uid;
- new.ssi_ptr = (long) kinfo->si_ptr;
- new.ssi_int = kinfo->si_int;
- break;
- case SIL_SYS:
- new.ssi_call_addr = (long) kinfo->si_call_addr;
- new.ssi_syscall = kinfo->si_syscall;
- new.ssi_arch = kinfo->si_arch;
- break;
- }
- if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
- return -EFAULT;
- return sizeof(*uinfo);
- }
- static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
- int nonblock)
- {
- ssize_t ret;
- DECLARE_WAITQUEUE(wait, current);
- spin_lock_irq(¤t->sighand->siglock);
- ret = dequeue_signal(current, &ctx->sigmask, info);
- switch (ret) {
- case 0:
- if (!nonblock)
- break;
- ret = -EAGAIN;
- default:
- spin_unlock_irq(¤t->sighand->siglock);
- return ret;
- }
- add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
- for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
- ret = dequeue_signal(current, &ctx->sigmask, info);
- if (ret != 0)
- break;
- if (signal_pending(current)) {
- ret = -ERESTARTSYS;
- break;
- }
- spin_unlock_irq(¤t->sighand->siglock);
- schedule();
- spin_lock_irq(¤t->sighand->siglock);
- }
- spin_unlock_irq(¤t->sighand->siglock);
- remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
- __set_current_state(TASK_RUNNING);
- return ret;
- }
- /*
- * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
- * error code. The "count" parameter must be at least the size of a
- * "struct signalfd_siginfo".
- */
- static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
- loff_t *ppos)
- {
- struct signalfd_ctx *ctx = file->private_data;
- struct signalfd_siginfo __user *siginfo;
- int nonblock = file->f_flags & O_NONBLOCK;
- ssize_t ret, total = 0;
- siginfo_t info;
- count /= sizeof(struct signalfd_siginfo);
- if (!count)
- return -EINVAL;
- siginfo = (struct signalfd_siginfo __user *) buf;
- do {
- ret = signalfd_dequeue(ctx, &info, nonblock);
- if (unlikely(ret <= 0))
- break;
- ret = signalfd_copyinfo(siginfo, &info);
- if (ret < 0)
- break;
- siginfo++;
- total += ret;
- nonblock = 1;
- } while (--count);
- return total ? total: ret;
- }
- #ifdef CONFIG_PROC_FS
- static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
- {
- struct signalfd_ctx *ctx = f->private_data;
- sigset_t sigmask;
- sigmask = ctx->sigmask;
- signotset(&sigmask);
- render_sigset_t(m, "sigmask:\t", &sigmask);
- }
- #endif
- static const struct file_operations signalfd_fops = {
- #ifdef CONFIG_PROC_FS
- .show_fdinfo = signalfd_show_fdinfo,
- #endif
- .release = signalfd_release,
- .poll = signalfd_poll,
- .read = signalfd_read,
- .llseek = noop_llseek,
- };
- static int do_signalfd4(int ufd, sigset_t *mask, int flags)
- {
- struct signalfd_ctx *ctx;
- /* Check the SFD_* constants for consistency. */
- BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
- BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
- if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
- return -EINVAL;
- sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
- signotset(mask);
- if (ufd == -1) {
- ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
- if (!ctx)
- return -ENOMEM;
- ctx->sigmask = *mask;
- /*
- * When we call this, the initialization must be complete, since
- * anon_inode_getfd() will install the fd.
- */
- ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
- O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
- if (ufd < 0)
- kfree(ctx);
- } else {
- struct fd f = fdget(ufd);
- if (!f.file)
- return -EBADF;
- ctx = f.file->private_data;
- if (f.file->f_op != &signalfd_fops) {
- fdput(f);
- return -EINVAL;
- }
- spin_lock_irq(¤t->sighand->siglock);
- ctx->sigmask = *mask;
- spin_unlock_irq(¤t->sighand->siglock);
- wake_up(¤t->sighand->signalfd_wqh);
- fdput(f);
- }
- return ufd;
- }
- SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
- size_t, sizemask, int, flags)
- {
- sigset_t mask;
- if (sizemask != sizeof(sigset_t) ||
- copy_from_user(&mask, user_mask, sizeof(mask)))
- return -EINVAL;
- return do_signalfd4(ufd, &mask, flags);
- }
- SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
- size_t, sizemask)
- {
- sigset_t mask;
- if (sizemask != sizeof(sigset_t) ||
- copy_from_user(&mask, user_mask, sizeof(mask)))
- return -EINVAL;
- return do_signalfd4(ufd, &mask, 0);
- }
- #ifdef CONFIG_COMPAT
- static long do_compat_signalfd4(int ufd,
- const compat_sigset_t __user *user_mask,
- compat_size_t sigsetsize, int flags)
- {
- sigset_t mask;
- if (sigsetsize != sizeof(compat_sigset_t))
- return -EINVAL;
- if (get_compat_sigset(&mask, user_mask))
- return -EFAULT;
- return do_signalfd4(ufd, &mask, flags);
- }
- COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
- const compat_sigset_t __user *, user_mask,
- compat_size_t, sigsetsize,
- int, flags)
- {
- return do_compat_signalfd4(ufd, user_mask, sigsetsize, flags);
- }
- COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
- const compat_sigset_t __user *, user_mask,
- compat_size_t, sigsetsize)
- {
- return do_compat_signalfd4(ufd, user_mask, sigsetsize, 0);
- }
- #endif
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