Subject: [PATCH] flow_offload: Annotate struct flow_action_entry with __counted_by

From: Kees Cook <[email-masked]>
Date: Tue, 3 Oct 2023 16:18:33 -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 flow_action_entry.

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/flow_offload.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
index 9efa9a59e81f..314087a5e181 100644
--- a/include/net/flow_offload.h
+++ b/include/net/flow_offload.h
@@ -333,7 +333,7 @@ struct flow_action_entry {
 
 struct flow_action {
 	unsigned int			num_entries;
-	struct flow_action_entry	entries[];
+	struct flow_action_entry	entries[] __counted_by(num_entries);
 };
 
 static inline bool flow_action_has_entries(const struct flow_action *action)
-- 
2.34.1