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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Ronnie Sahlberg <lsahlber@redhat.com>,
	Steve French <stfrench@microsoft.com>,
	Sasha Levin <sashal@kernel.org>,
	linux-cifs@vger.kernel.org, samba-technical@lists.samba.org
Subject: [PATCH AUTOSEL 4.14 165/186] cifs: fix NULL dereference in match_prepath
Date: Fri, 14 Feb 2020 11:16:54 -0500
Message-ID: <20200214161715.18113-165-sashal@kernel.org> (raw)
In-Reply-To: <20200214161715.18113-1-sashal@kernel.org>

From: Ronnie Sahlberg <lsahlber@redhat.com>

[ Upstream commit fe1292686333d1dadaf84091f585ee903b9ddb84 ]

RHBZ: 1760879

Fix an oops in match_prepath() by making sure that the prepath string is not
NULL before we pass it into strcmp().

This is similar to other checks we make for example in cifs_root_iget()

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/connect.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index f0b1279a7de66..6e5ecf70996a0 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3047,8 +3047,10 @@ match_prepath(struct super_block *sb, struct cifs_mnt_data *mnt_data)
 {
 	struct cifs_sb_info *old = CIFS_SB(sb);
 	struct cifs_sb_info *new = mnt_data->cifs_sb;
-	bool old_set = old->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH;
-	bool new_set = new->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH;
+	bool old_set = (old->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) &&
+		old->prepath;
+	bool new_set = (new->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) &&
+		new->prepath;
 
 	if (old_set && new_set && !strcmp(new->prepath, old->prepath))
 		return 1;
-- 
2.20.1


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