Subject: [PATCH] nexthop: Annotate struct nh_res_table with __counted_by

From: Kees Cook <[email-masked]>
Date: Tue, 3 Oct 2023 16:18:13 -0700

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct nh_res_table.

Cc: David Ahern <[email-masked]>
Cc: "David S. Miller" <[email-masked]>
Cc: Eric Dumazet <[email-masked]>
Cc: Jakub Kicinski <[email-masked]>
Cc: Paolo Abeni <[email-masked]>
Cc: [email-masked]
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <[email-masked]>
---
 include/net/nexthop.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index 5dc4b4bba8a5..09f9a732e640 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -92,7 +92,7 @@ struct nh_res_table {
 	u32			unbalanced_timer;
 
 	u16			num_nh_buckets;
-	struct nh_res_bucket	nh_buckets[];
+	struct nh_res_bucket	nh_buckets[] __counted_by(num_nh_buckets);
 };
 
 struct nh_grp_entry {
-- 
2.34.1