Subject: [PATCH] ipv4/fib: Replace zero-length array with DECLARE_FLEX_ARRAY() helper

From: Kees Cook <[email-masked]>
Date: Thu, 17 Nov 2022 20:21:52 -0800

Zero-length arrays are deprecated[1] and are being replaced with
flexible array members in support of the ongoing efforts to tighten the
FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.

Replace zero-length array with flexible-array member in struct key_vector.

This results in no differences in binary output.

[1] https://github.com/KSPP/linux/issues/78

Cc: Jakub Kicinski <[email-masked]>
Cc: "David S. Miller" <[email-masked]>
Cc: Hideaki YOSHIFUJI <[email-masked]>
Cc: David Ahern <[email-masked]>
Cc: Eric Dumazet <[email-masked]>
Cc: Paolo Abeni <[email-masked]>
Cc: "Gustavo A. R. Silva" <[email-masked]>
Cc: [email-masked]
Signed-off-by: Kees Cook <[email-masked]>
---
 net/ipv4/fib_trie.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 452ff177e4da..c88bf856c443 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -126,7 +126,7 @@ struct key_vector {
 		/* This list pointer if valid if (pos | bits) == 0 (LEAF) */
 		struct hlist_head leaf;
 		/* This array is valid if (pos | bits) > 0 (TNODE) */
-		struct key_vector __rcu *tnode[0];
+		DECLARE_FLEX_ARRAY(struct key_vector __rcu *, tnode);
 	};
 };
 
-- 
2.34.1