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. Also move the assignment of temp_len above so that we need not call strlen(value) twice.

Signed-off-by Suresh Jayaraman <sjayaraman-IBi9RG/[email protected]>

---
 fs/cifs/connect.c |   37 ++++++++++++++++++++-----------------
 1 files changed, 20 insertions(+), 17 deletions(-)

fs/cifs/connect.c +13 -16

index 78db68a..fdbbb56 100644
@@ -1646,34 +1646,37 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			value = strchr(data, '=');
 			value++;
 
+			temp_len = strlen(value);
+
 			/* Set tmp_end to end of the string */
-			tmp_end = (char *) value + strlen(value);
+			tmp_end = (char *) value + temp_len;
 
 			/* Check if following character is the deliminator
 			 * 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) {

Quoted 81 lines · Suresh Jayaraman

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. Also move the assignment of temp_len above so that we need not call strlen(value) twice.

Signed-off-by Suresh Jayaraman <sjayaraman-IBi9RG/[email protected]>

---
 fs/cifs/connect.c |   37 ++++++++++++++++++++-----------------
 1 files changed, 20 insertions(+), 17 deletions(-)

fs/cifs/connect.c +20 -16

index 78db68a..fdbbb56 100644
@@ -1646,34 +1646,37 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			value = strchr(data, '=');
 			value++;
 
+			temp_len = strlen(value);
+
 			/* Set tmp_end to end of the string */
-			tmp_end = (char *) value + strlen(value);
+			tmp_end = (char *) value + temp_len;
 
 			/* Check if following character is the deliminator
 			 * 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;
+			}
 

fs/cifs/connect.c cifs_parse_mount_options(const char *mountdata, const char *devname, · line 1676

Quoted 2 lines

fs/cifs/connect.c +0 -1

 			/* Now build new password string */
-			temp_len = strlen(value);

The bug fix is correct but you cannot optimise the second strlen() call in this manner since at this point if we had encountered a double delimiter the end of the value string is shifted down further until we

Wouldn't this also have to go cc: stable since it involves password check logic in last release too?