cifs: fix parsing of password mount option

The double delimiter check that allows a comma in the password parsing code is
unconditional. We set "tmp_end" to the end of the string and we continue to
check for double delimiter. In the case where the password doesn't contain a
comma we end up setting tmp_end to NULL and eventually setting "options" to
"end". This results in the premature termination of the options string and hence
the values of UNCip and UNC are being set to NULL. This results in mount failure
with "Connecting to DFS root not implemented yet" error.

This error is usually not noticable as we have password as the last option in
the superblock mountdata. But when we call expand_dfs_referral() from
cifs_mount() and try to compose mount options for the submount, the resulting
mountdata will be of the form

   ",ver=1,user=foo,pass=bar,ip=x.x.x.x,unc=\\server\share"

and hence results in the above error. This bug has been seen with older NAS
servers running Samba 3.0.24.

Fix this by moving the double delimiter check inside the conditional loop.

Changes since -v1

   - removed the wrong strlen() micro optimization.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.com>
Acked-by: Sachin Prabhu <sprabhu@redhat.com>
Cc: stable@vger.kernel.org [3.1+]
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 17 insertions, 15 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 78db68a5cf44..5b3840725d01 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1653,24 +1653,26 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
                          * If yes, we have encountered a double deliminator
                          * reset the NULL character to the deliminator
                          */
-                        if (tmp_end < end && tmp_end[1] == delim)
+                        if (tmp_end < end && tmp_end[1] == delim) {
                                 tmp_end[0] = delim;
 
-                        /* Keep iterating until we get to a single deliminator
-                         * OR the end
-                         */
-                        while ((tmp_end = strchr(tmp_end, delim)) != NULL &&
-                               (tmp_end[1] == delim)) {
-                                tmp_end = (char *) &tmp_end[2];
-                        }
+                                /* Keep iterating until we get to a single
+                                 * deliminator OR the end
+                                 */
+                                while ((tmp_end = strchr(tmp_end, delim))
+                                        != NULL && (tmp_end[1] == delim)) {
+                                                tmp_end = (char *) &tmp_end[2];
+                                }
 
-                        /* Reset var options to point to next element */
-                        if (tmp_end) {
-                                tmp_end[0] = '\0';
-                                options = (char *) &tmp_end[1];
-                        } else
-                                /* Reached the end of the mount option string */
-                                options = end;
+                                /* Reset var options to point to next element */
+                                if (tmp_end) {
+                                        tmp_end[0] = '\0';
+                                        options = (char *) &tmp_end[1];
+                                } else
+                                        /* Reached the end of the mount option
+                                         * string */
+                                        options = end;
+                        }
 
                         /* Now build new password string */
                         temp_len = strlen(value);