[PATCH] cifs: ensure that vol->username is not NULL before running strlen on it

[Jeff Layton]

Dan Carpenter says:

The patch 04febabcf55b: "cifs: sanitize username handling" from Jan
17, 2012, leads to the following static checker warning:

fs/cifs/connect.c:2231 match_session()
error: we previously assumed 'vol->username' could be null (see line 2228)

fs/cifs/connect.c
2219 /* NULL username means anonymous session */
2220 if (ses->user_name == NULL) {
2221 if (!vol->nullauth)
2222 return 0;
2223 break;
2224 }
2225
2226 /* anything else takes username/password */
2227 if (strncmp(ses->user_name,
2228 vol->username ? vol->username : "",
^^^^^^^^^^^^^
We added this check for vol->username here.

2229 CIFS_MAX_USERNAME_LEN))
2230 return 0;
2231 if (strlen(vol->username) != 0 &&
^^^^^^^^^^^^^
But this dereference is not checked.

2232 ses->password != NULL &&
2233 strncmp(ses->password,
2234 vol->password ? vol->password : "",
2235 CIFS_MAX_PASSWORD_LEN))
2236 return 0;

...fix this by ensuring that vol->username is not NULL before running
strlen on it.

Signed-off-by: Jeff Layton <jlayton-vpEMnDpepFuMZCB2o+***@public.gmane.org>
Reported-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+***@public.gmane.org>
---
fs/cifs/connect.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 8b8fe9b373f2..20d75b8ddb26 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2228,7 +2228,7 @@ static int match_session(struct cifs_ses *ses, struct smb_vol *vol)
vol->username ? vol->username : "",
CIFS_MAX_USERNAME_LEN))
return 0;
- if (strlen(vol->username) != 0 &&
+ if ((vol->username && strlen(vol->username) != 0) &&
ses->password != NULL &&
strncmp(ses->password,
vol->password ? vol->password : "",