Unverified Commit 6b47d35d authored by Jens Axboe's avatar Jens Axboe Committed by Christian Brauner
Browse files

eventpoll: abstract out parameter sanity checking 



Add a helper that checks the validity of the file descriptor and
other parameters passed in to epoll_wait().

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20250219172552.1565603-2-axboe@kernel.dk


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 2014c95a

fs/eventpoll.c

+25 −14
Original line number Diff line number Diff line
@@ -2445,6 +2445,27 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, 
	return do_epoll_ctl(epfd, op, fd, &epds, false);

}



static int ep_check_params(struct file *file, struct epoll_event __user *evs,

			   int maxevents)

{

	/* The maximum number of event must be greater than zero */

	if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)

		return -EINVAL;



	/* Verify that the area passed by the user is writeable */

	if (!access_ok(evs, maxevents * sizeof(struct epoll_event)))

		return -EFAULT;



	/*

	 * We have to check that the file structure underneath the fd

	 * the user passed to us _is_ an eventpoll file.

	 */

	if (!is_file_epoll(file))

		return -EINVAL;



	return 0;

}



/*

 * Implement the event wait interface for the eventpoll file. It is the kernel

 * part of the user space epoll_wait(2).
@@ -2453,26 +2474,16 @@ static int do_epoll_wait(int epfd, struct epoll_event __user *events, 
			 int maxevents, struct timespec64 *to)

{

	struct eventpoll *ep;



	/* The maximum number of event must be greater than zero */

	if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)

		return -EINVAL;



	/* Verify that the area passed by the user is writeable */

	if (!access_ok(events, maxevents * sizeof(struct epoll_event)))

		return -EFAULT;

	int ret;



	/* Get the "struct file *" for the eventpoll file */

	CLASS(fd, f)(epfd);

	if (fd_empty(f))

		return -EBADF;



	/*

	 * We have to check that the file structure underneath the fd

	 * the user passed to us _is_ an eventpoll file.

	 */

	if (!is_file_epoll(fd_file(f)))

		return -EINVAL;

	ret = ep_check_params(fd_file(f), events, maxevents);

	if (unlikely(ret))

		return ret;



	/*

	 * At this point it is safe to assume that the "private_data" contains