diff mbox series

[5.4,059/129] fix regression in "epoll: Keep a reference on files added to the check list"

Message ID 20200908152232.650771273@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH Sept. 8, 2020, 3:25 p.m. UTC 
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(-)
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Patch

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 0d9b1e2b9da72..ae1d32344f7ac 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1992,9 +1992,9 @@  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);
 			}
 		}
 	}