[PATCH 4.4 17/62] fix regression in "epoll: Keep a reference on files added to the check list"

Greg Kroah-Hartman
2020-09-11T17:35:58Z

From: Al Viro <viro@zeniv.linux.org.uk>

[ Upstream commit 77f4689de17c0887775bb77896f4cc11a39bf848 ]

epoll_loop_check_proc() can run into a file already committed to destruction;
we can't grab a reference on those and don't need to add them to the set for
reverse path check anyway.

Tested-by: Marc Zyngier <maz@kernel.org>
Fixes: a9ed4a6560b8 ("epoll: Keep a reference on files added to the check list")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/eventpoll.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index b8959d0d4c723..e5324642023d6 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1720,9 +1720,9 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
* during ep_insert().
*/
if (list_empty(&epi->ffd.file->f_tfile_llink)) {
- get_file(epi->ffd.file);
- list_add(&epi->ffd.file->f_tfile_llink,
- &tfile_check_list);
+ if (get_file_rcu(epi->ffd.file))
+ list_add(&epi->ffd.file->f_tfile_llink,
+ &tfile_check_list);
}
}
}
--
2.25.1