Commit c857ab64 authored Feb 27, 2017 by Cyrill Gorcunov Committed by Linus Torvalds Feb 27, 2017

fs,eventpoll: don't test for bitfield with stack value

In case if epoll_ctl is called with operation EPOLL_CTL_DEL then
@epds.events variable allocated on stack may contain random bits which
we test then for EPOLLEXCLUSIVE.  Since currently the test look like

	if (epds.events & EPOLLEXCLUSIVE) {
		if (op == EPOLL_CTL_MOD)
			goto error_tgt_fput;
		if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) ||
				(epds.events & ~EPOLLEXCLUSIVE_OK_BITS)))
			goto error_tgt_fput;
	}

Nothing serious will happen even if epds.events has this bit set, still
better to be on safe side and make sure that we're to test this bit at
all.

Link: http://lkml.kernel.org/r/20170214154935.GG1850@uranus.lan


Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrey Vagin <avagin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e3b5a342

fs/eventpoll.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1895,7 +1895,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
		* so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation.
		* Also, we do not currently supported nested exclusive wakeups.
		*/
		if (epds.events & EPOLLEXCLUSIVE) {
		if (ep_op_has_event(op) && (epds.events & EPOLLEXCLUSIVE)) {
		if (op == EPOLL_CTL_MOD)
		goto error_tgt_fput;
		if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) \|\|

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