cifs: do not use uninitialized data in the owner/group sid

BugLink: https://bugs.launchpad.net/bugs/2036450

When idsfromsid is used we create a special SID for owner/group.
This structure must be initialized or else the first 5 bytes
of the Authority field of the SID will contain uninitialized data
and thus not be a valid SID.

Signed-off-by: Ronnie Sahlberg <[email protected]>
Signed-off-by: Steve French <[email protected]>
(cherry picked from commit 26d3dad)
Signed-off-by: Tim Gardner <[email protected]>

Author: Ronnie Sahlberg

fs/cifs/cifsacl.c

@@ -1297,7 +1297,7 @@ static int build_sec_desc(struct cifs_ntsd *pntsd, struct cifs_ntsd *pnntsd,
 
 		if (uid_valid(uid)) { /* chown */
 			uid_t id;
-			nowner_sid_ptr = kmalloc(sizeof(struct cifs_sid),
+			nowner_sid_ptr = kzalloc(sizeof(struct cifs_sid),
 								GFP_KERNEL);
 			if (!nowner_sid_ptr) {
 				rc = -ENOMEM;
@@ -1326,7 +1326,7 @@ static int build_sec_desc(struct cifs_ntsd *pntsd, struct cifs_ntsd *pnntsd,
 		}
 		if (gid_valid(gid)) { /* chgrp */
 			gid_t id;
-			ngroup_sid_ptr = kmalloc(sizeof(struct cifs_sid),
+			ngroup_sid_ptr = kzalloc(sizeof(struct cifs_sid),
 								GFP_KERNEL);
 			if (!ngroup_sid_ptr) {
 				rc = -ENOMEM;