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

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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/[email protected]
Signed-off-by: Cyrill Gorcunov <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrey Vagin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Cyrill Gorcunov 2017-02-27 14:27:40 -08:00 • committed by Linus Torvalds
commit c857ab640c
1 changed files with 1 additions and 1 deletions
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2
fs/eventpoll.c
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@ -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) ||