smb: propagate error code of extract_sharename()

In addition to the EINVAL, there may be an ENOMEM.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 70431bfd ("cifs: Support fscache indexing rewrite")
Signed-off-by: Katya Orlova <e.orlova@ispras.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/fscache.c

@@ -48,7 +48,7 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon)
 	sharename = extract_sharename(tcon->tree_name);
 	if (IS_ERR(sharename)) {
 		cifs_dbg(FYI, "%s: couldn't extract sharename\n", __func__);
-		return -EINVAL;
+		return PTR_ERR(sharename);
 	}
 
 	slen = strlen(sharename);