[PATCH 5.4 304/344] cifs: fix NULL dereference in match_prepath

Greg Kroah-Hartman
2020-02-21T08:14:27Z

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 02451d085ddd0..5d3c867bdc808 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3652,8 +3652,10 @@ 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