From c857ab640c0cddf451cf743f1b70f9ad7f103090 Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Mon, 27 Feb 2017 14:27:40 -0800 Subject: [PATCH] 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 Cc: Al Viro Cc: Andrey Vagin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/eventpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index bcb68fcc8445..5ec16313da1a 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -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) || -- 2.20.1