[PATCH 2/2] smb: client: prevent out-of-bounds dfs_info3_param access in copy_ref_data()

[Fredric Cover <fredric.cover.lkernel@gmail.com>]

Currently, copy_ref_data() assumes that numrefs > 0, and unconditinally
accesses refs[0]. If copy_ref_data() somehow is passed an empty list,
this would cause major out-of-bounds write and read problems.

Enforce numrefs > 0.

Signed-off-by: Fredric Cover <fredric.cover.lkernel@gmail.com>
---
 fs/smb/client/dfs_cache.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/smb/client/dfs_cache.c b/fs/smb/client/dfs_cache.c
index b0388c460499..b51c8355d73d 100644
--- a/fs/smb/client/dfs_cache.c
+++ b/fs/smb/client/dfs_cache.c
@@ -389,6 +389,9 @@ static int copy_ref_data(const struct dfs_info3_param *refs, int numrefs,
 	struct cache_dfs_tgt *target;
 	int i;
 
+	if (WARN_ON_ONCE(numrefs <= 0))
+		return -EINVAL;
+
 	for (i = 0; i < numrefs; i++) {
 		struct cache_dfs_tgt *t;
 
-- 
2.53.0