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[5.5,351/399] cifs: fix NULL dereference in match_prepath

Message ID 20200221072435.165073948@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg KH Feb. 21, 2020, 7:41 a.m. UTC 
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(-)
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Patch

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 05ea0e2b7e0e8..0aa3623ae0e16 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3709,8 +3709,10 @@  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;