fs/signalfd.c - linux - Git at Google

 // 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)
 {
 	wake_up_pollfree(&sighand->signalfd_wqh);
 }

 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, &current->sighand->signalfd_wqh, wait);

 	spin_lock_irq(&current->sighand->siglock);
 	if (next_signal(&current->pending, &ctx->sigmask) ||
 	    next_signal(&current->signal->shared_pending,
 			&ctx->sigmask))
 		events |= EPOLLIN;
 	spin_unlock_irq(&current->sighand->siglock);

 	return events;
 }

 /*
  * Copied from copy_siginfo_to_user() in kernel/signal.c
  */
 static int signalfd_copyinfo(struct iov_iter *to, kernel_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:
 	case SIL_FAULT_PERF_EVENT:
 		/*
 		 * Fall through to the SIL_FAULT case.  SIL_FAULT_BNDERR,
 		 * SIL_FAULT_PKUERR, and SIL_FAULT_PERF_EVENT 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;
 		break;
 	case SIL_FAULT_TRAPNO:
 		new.ssi_addr = (long) kinfo->si_addr;
 		new.ssi_trapno = kinfo->si_trapno;
 		break;
 	case SIL_FAULT_MCEERR:
 		new.ssi_addr = (long) kinfo->si_addr;
 		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_iter_full(&new, sizeof(struct signalfd_siginfo), to))
 		return -EFAULT;

 	return sizeof(struct signalfd_siginfo);
 }

 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
 				int nonblock)
 {
 	enum pid_type type;
 	ssize_t ret;
 	DECLARE_WAITQUEUE(wait, current);

 	spin_lock_irq(&current->sighand->siglock);
 	ret = dequeue_signal(&ctx->sigmask, info, &type);
 	switch (ret) {
 	case 0:
 		if (!nonblock)
 			break;
 		ret = -EAGAIN;
 		fallthrough;
 	default:
 		spin_unlock_irq(&current->sighand->siglock);
 		return ret;
 	}

 	add_wait_queue(&current->sighand->signalfd_wqh, &wait);
 	for (;;) {
 		set_current_state(TASK_INTERRUPTIBLE);
 		ret = dequeue_signal(&ctx->sigmask, info, &type);
 		if (ret != 0)
 			break;
 		if (signal_pending(current)) {
 			ret = -ERESTARTSYS;
 			break;
 		}
 		spin_unlock_irq(&current->sighand->siglock);
 		schedule();
 		spin_lock_irq(&current->sighand->siglock);
 	}
 	spin_unlock_irq(&current->sighand->siglock);

 	remove_wait_queue(&current->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_iter(struct kiocb *iocb, struct iov_iter *to)
 {
 	struct file *file = iocb->ki_filp;
 	struct signalfd_ctx *ctx = file->private_data;
 	size_t count = iov_iter_count(to);
 	ssize_t ret, total = 0;
 	kernel_siginfo_t info;
 	bool nonblock;

 	count /= sizeof(struct signalfd_siginfo);
 	if (!count)
 		return -EINVAL;

 	nonblock = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
 	do {
 		ret = signalfd_dequeue(ctx, &info, nonblock);
 		if (unlikely(ret <= 0))
 			break;
 		ret = signalfd_copyinfo(to, &info);
 		if (ret < 0)
 			break;
 		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_iter	= signalfd_read_iter,
 	.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) {
 		struct file *file;

 		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
 		if (!ctx)
 			return -ENOMEM;

 		ctx->sigmask = *mask;

 		ufd = get_unused_fd_flags(flags & O_CLOEXEC);
 		if (ufd < 0) {
 			kfree(ctx);
 			return ufd;
 		}

 		file = anon_inode_getfile("[signalfd]", &signalfd_fops, ctx,
 				       O_RDWR | (flags & O_NONBLOCK));
 		if (IS_ERR(file)) {
 			put_unused_fd(ufd);
 			kfree(ctx);
 			return PTR_ERR(file);
 		}
 		file->f_mode |= FMODE_NOWAIT;

 		fd_install(ufd, file);
 	} else {
 		CLASS(fd, f)(ufd);
 		if (fd_empty(f))
 			return -EBADF;
 		ctx = fd_file(f)->private_data;
 		if (fd_file(f)->f_op != &signalfd_fops)
 			return -EINVAL;
 		spin_lock_irq(&current->sighand->siglock);
 		ctx->sigmask = *mask;
 		spin_unlock_irq(&current->sighand->siglock);

 		wake_up(&current->sighand->signalfd_wqh);
 	}

 	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))
 		return -EINVAL;
 	if (copy_from_user(&mask, user_mask, sizeof(mask)))
 		return -EFAULT;
 	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))
 		return -EINVAL;
 	if (copy_from_user(&mask, user_mask, sizeof(mask)))
 		return -EFAULT;
 	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
	// 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)
	{
	wake_up_pollfree(&sighand->signalfd_wqh);
	}

	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, &current->sighand->signalfd_wqh, wait);

	spin_lock_irq(&current->sighand->siglock);
	if (next_signal(&current->pending, &ctx->sigmask) \|\|
	next_signal(&current->signal->shared_pending,
	&ctx->sigmask))
	events \|= EPOLLIN;
	spin_unlock_irq(&current->sighand->siglock);

	return events;
	}

	/*
	* Copied from copy_siginfo_to_user() in kernel/signal.c
	*/
	static int signalfd_copyinfo(struct iov_iter to, kernel_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:
	case SIL_FAULT_PERF_EVENT:
	/*
	* Fall through to the SIL_FAULT case. SIL_FAULT_BNDERR,
	* SIL_FAULT_PKUERR, and SIL_FAULT_PERF_EVENT 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;
	break;
	case SIL_FAULT_TRAPNO:
	new.ssi_addr = (long) kinfo->si_addr;
	new.ssi_trapno = kinfo->si_trapno;
	break;
	case SIL_FAULT_MCEERR:
	new.ssi_addr = (long) kinfo->si_addr;
	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_iter_full(&new, sizeof(struct signalfd_siginfo), to))
	return -EFAULT;

	return sizeof(struct signalfd_siginfo);
	}

	static ssize_t signalfd_dequeue(struct signalfd_ctx ctx, kernel_siginfo_t info,
	int nonblock)
	{
	enum pid_type type;
	ssize_t ret;
	DECLARE_WAITQUEUE(wait, current);

	spin_lock_irq(&current->sighand->siglock);
	ret = dequeue_signal(&ctx->sigmask, info, &type);
	switch (ret) {
	case 0:
	if (!nonblock)
	break;
	ret = -EAGAIN;
	fallthrough;
	default:
	spin_unlock_irq(&current->sighand->siglock);
	return ret;
	}

	add_wait_queue(&current->sighand->signalfd_wqh, &wait);
	for (;;) {
	set_current_state(TASK_INTERRUPTIBLE);
	ret = dequeue_signal(&ctx->sigmask, info, &type);
	if (ret != 0)
	break;
	if (signal_pending(current)) {
	ret = -ERESTARTSYS;
	break;
	}
	spin_unlock_irq(&current->sighand->siglock);
	schedule();
	spin_lock_irq(&current->sighand->siglock);
	}
	spin_unlock_irq(&current->sighand->siglock);

	remove_wait_queue(&current->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_iter(struct kiocb iocb, struct iov_iter to)
	{
	struct file *file = iocb->ki_filp;
	struct signalfd_ctx *ctx = file->private_data;
	size_t count = iov_iter_count(to);
	ssize_t ret, total = 0;
	kernel_siginfo_t info;
	bool nonblock;

	count /= sizeof(struct signalfd_siginfo);
	if (!count)
	return -EINVAL;

	nonblock = file->f_flags & O_NONBLOCK \|\| iocb->ki_flags & IOCB_NOWAIT;
	do {
	ret = signalfd_dequeue(ctx, &info, nonblock);
	if (unlikely(ret <= 0))
	break;
	ret = signalfd_copyinfo(to, &info);
	if (ret < 0)
	break;
	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_iter = signalfd_read_iter,
	.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) {
	struct file *file;

	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
	if (!ctx)
	return -ENOMEM;

	ctx->sigmask = *mask;

	ufd = get_unused_fd_flags(flags & O_CLOEXEC);
	if (ufd < 0) {
	kfree(ctx);
	return ufd;
	}

	file = anon_inode_getfile("[signalfd]", &signalfd_fops, ctx,
	O_RDWR \| (flags & O_NONBLOCK));
	if (IS_ERR(file)) {
	put_unused_fd(ufd);
	kfree(ctx);
	return PTR_ERR(file);
	}
	file->f_mode \|= FMODE_NOWAIT;

	fd_install(ufd, file);
	} else {
	CLASS(fd, f)(ufd);
	if (fd_empty(f))
	return -EBADF;
	ctx = fd_file(f)->private_data;
	if (fd_file(f)->f_op != &signalfd_fops)
	return -EINVAL;
	spin_lock_irq(&current->sighand->siglock);
	ctx->sigmask = *mask;
	spin_unlock_irq(&current->sighand->siglock);

	wake_up(&current->sighand->signalfd_wqh);
	}

	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))
	return -EINVAL;
	if (copy_from_user(&mask, user_mask, sizeof(mask)))
	return -EFAULT;
	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))
	return -EINVAL;
	if (copy_from_user(&mask, user_mask, sizeof(mask)))
	return -EFAULT;
	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