linux-kernel - [PATCH AUTOSEL 5.4 5/5] ovl: fix uninitialized pointer read in ovl_lookup_real

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Message-Id: <20210817003607.83340-5-sashal@kernel.org>
Date:   Mon, 16 Aug 2021 20:36:07 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Miklos Szeredi <mszeredi@...hat.com>,
        Colin Ian King <colin.king@...onical.com>,
        Sasha Levin <sashal@...nel.org>, linux-unionfs@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 5/5] ovl: fix uninitialized pointer read in ovl_lookup_real_one()

From: Miklos Szeredi <mszeredi@...hat.com>

[ Upstream commit 580c610429b3994e8db24418927747cf28443cde ]

One error path can result in release_dentry_name_snapshot() being called
before "name" was initialized by take_dentry_name_snapshot().

Fix by moving the release_dentry_name_snapshot() to immediately after the
only use.

Reported-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/overlayfs/export.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 11dd8177770d..19574ef17470 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -395,6 +395,7 @@ static struct dentry *ovl_lookup_real_one(struct dentry *connected,
 	 */
 	take_dentry_name_snapshot(&name, real);
 	this = lookup_one_len(name.name.name, connected, name.name.len);
+	release_dentry_name_snapshot(&name);
 	err = PTR_ERR(this);
 	if (IS_ERR(this)) {
 		goto fail;
@@ -409,7 +410,6 @@ static struct dentry *ovl_lookup_real_one(struct dentry *connected,
 	}
 
 out:
-	release_dentry_name_snapshot(&name);
 	dput(parent);
 	inode_unlock(dir);
 	return this;
-- 
2.30.2