linux-kernel - [PATCH AUTOSEL 5.8 05/12] ep_create_wakeup_source(): dentry name can change under you...

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Date:   Mon,  5 Oct 2020 10:44:53 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Al Viro <viro@...iv.linux.org.uk>, Sasha Levin <sashal@...nel.org>,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.8 05/12] ep_create_wakeup_source(): dentry name can change under you...

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

[ Upstream commit 3701cb59d892b88d569427586f01491552f377b1 ]

or get freed, for that matter, if it's a long (separately stored)
name.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/eventpoll.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 16313180e4c16..4df61129566d4 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1448,7 +1448,7 @@ static int reverse_path_check(void)
 
 static int ep_create_wakeup_source(struct epitem *epi)
 {
-	const char *name;
+	struct name_snapshot n;
 	struct wakeup_source *ws;
 
 	if (!epi->ep->ws) {
@@ -1457,8 +1457,9 @@ static int ep_create_wakeup_source(struct epitem *epi)
 			return -ENOMEM;
 	}
 
-	name = epi->ffd.file->f_path.dentry->d_name.name;
-	ws = wakeup_source_register(NULL, name);
+	take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);
+	ws = wakeup_source_register(NULL, n.name.name);
+	release_dentry_name_snapshot(&n);
 
 	if (!ws)
 		return -ENOMEM;
-- 
2.25.1