linux-kernel - [PATCH] watch_queue: Annotate struct watch_filter with __counted

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Message-Id: <20230922175407.work.754-kees@kernel.org>
Date:   Fri, 22 Sep 2023 10:54:08 -0700
From:   Kees Cook <keescook@...omium.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Siddh Raman Pant <code@...dh.me>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Qian Cai <cai@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: [PATCH] watch_queue: Annotate struct watch_filter 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 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 watch_filter.

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

Cc: David Howells <dhowells@...hat.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Christian Brauner <brauner@...nel.org>
Cc: Jonathan Corbet <corbet@....net>
Cc: Siddh Raman Pant <code@...dh.me>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Qian Cai <cai@...hat.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/watch_queue.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
index 45cd42f55d49..429c7b6afead 100644
--- a/include/linux/watch_queue.h
+++ b/include/linux/watch_queue.h
@@ -32,7 +32,7 @@ struct watch_filter {
 		DECLARE_BITMAP(type_filter, WATCH_TYPE__NR);
 	};
 	u32			nr_filters;	/* Number of filters */
-	struct watch_type_filter filters[];
+	struct watch_type_filter filters[] __counted_by(nr_filters);
 };
 
 struct watch_queue {
-- 
2.34.1