dlm: validate length in dlm_search_rsb_tree

[ Upstream commit 080e556 ]

The len parameter in dlm_dump_rsb_name() is not validated and comes
from network messages. When it exceeds DLM_RESNAME_MAXLEN, it can
cause out-of-bounds write in dlm_search_rsb_tree().

Add length validation to prevent potential buffer overflow.

Signed-off-by: Ezrak1e <ezrakiez@gmail.com>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Ezrak1e

fs/dlm/lock.c

@@ -626,7 +626,8 @@ int dlm_search_rsb_tree(struct rhashtable *rhash, const void *name, int len,
 			struct dlm_rsb **r_ret)
 {
 	char key[DLM_RESNAME_MAXLEN] = {};
-
+	if (len > DLM_RESNAME_MAXLEN)
+		return -EINVAL;
 	memcpy(key, name, len);
 	*r_ret = rhashtable_lookup_fast(rhash, &key, dlm_rhash_rsb_params);
 	if (*r_ret)