netdev - [PATCH] flow_offload: Annotate struct flow_action_entry with __counted

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Message-Id: <20231003231833.work.027-kees@kernel.org>
Date: Tue,  3 Oct 2023 16:18:33 -0700
From: Kees Cook <keescook@...omium.org>
To: "David S. Miller" <davem@...emloft.net>
Cc: Kees Cook <keescook@...omium.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Tom Rix <trix@...hat.com>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] flow_offload: Annotate struct flow_action_entry with __counted_by

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" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 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