[PATCH] landlock: Annotate struct landlock_rule with __counted_by

[Kees Cook]

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 checking 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 landlock_rule.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: "Mickaël Salaün" <mic at digikod.net>
Cc: Paul Moore <paul at paul-moore.com>
Cc: James Morris <jmorris at namei.org>
Cc: "Serge E. Hallyn" <serge at hallyn.com>
Cc: linux-security-module at vger.kernel.org
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 security/landlock/ruleset.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index d43231b783e4..55b1df8f66a8 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -67,7 +67,7 @@ struct landlock_rule {
 	 * @layers: Stack of layers, from the latest to the newest, implemented
 	 * as a flexible array member (FAM).
 	 */
-	struct landlock_layer layers[];
+	struct landlock_layer layers[] __counted_by(num_layers);
 };
 
 /**
-- 
2.34.1