From: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrey Vagin <avagin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN fs/eventpoll.c~fseventpoll-dont-test-for-bitfield-with-stack-value fs/eventpoll.c
--- a/fs/eventpoll.c~fseventpoll-dont-test-for-bitfield-with-stack-value
+++ a/fs/eventpoll.c
@@ -1895,7 +1895,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, in
* 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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