[CIFS] cifs: fix oops on mount when CONFIG_CIFS_DFS_UPCALL is enabled

simple "mount -t cifs //xxx /mnt" oopsed on strlen of options
http://kerneloops.org/guilty.php?guilty=cifs_get_sb&version=2.6.25-release&start=16711 \
68&end=1703935&class=oops

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 10 insertions, 11 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 5df93fd6303..86b4d5f405a 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -97,9 +97,6 @@ cifs_read_super(struct super_block *sb, void *data,
 {
         struct inode *inode;
         struct cifs_sb_info *cifs_sb;
-#ifdef CONFIG_CIFS_DFS_UPCALL
-        int len;
-#endif
         int rc = 0;
 
         /* BB should we make this contingent on mount parm? */
@@ -117,15 +114,17 @@ cifs_read_super(struct super_block *sb, void *data,
          * complex operation (mount), and in case of fail
          * just exit instead of doing mount and attempting
          * undo it if this copy fails?*/
-        len = strlen(data);
-        cifs_sb->mountdata = kzalloc(len + 1, GFP_KERNEL);
-        if (cifs_sb->mountdata == NULL) {
-                kfree(sb->s_fs_info);
-                sb->s_fs_info = NULL;
-                return -ENOMEM;
+        if (data) {
+                int len = strlen(data);
+                cifs_sb->mountdata = kzalloc(len + 1, GFP_KERNEL);
+                if (cifs_sb->mountdata == NULL) {
+                        kfree(sb->s_fs_info);
+                        sb->s_fs_info = NULL;
+                        return -ENOMEM;
+                }
+                strncpy(cifs_sb->mountdata, data, len + 1);
+                cifs_sb->mountdata[len] = '\0';
         }
-        strncpy(cifs_sb->mountdata, data, len + 1);
-        cifs_sb->mountdata[len] = '\0';
 #endif
 
         rc = cifs_mount(sb, cifs_sb, data, devname);