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Date:   Sat, 23 Sep 2023 19:52:39 +0530
From:   Siddh Raman Pant <code@siddh.me>
To:     "Kees Cook" <keescook@chromium.org>
Cc:     "David Howells" <dhowells@redhat.com>,
        "Randy Dunlap" <rdunlap@infradead.org>,
        "Al Viro" <viro@zeniv.linux.org.uk>,
        "Christian Brauner" <brauner@kernel.org>,
        "Jonathan Corbet" <corbet@lwn.net>,
        "Mauro Carvalho Chehab" <mchehab@kernel.org>,
        "Qian Cai" <cai@redhat.com>,
        "Nathan Chancellor" <nathan@kernel.org>,
        "Nick Desaulniers" <ndesaulniers@google.com>,
        "Tom Rix" <trix@redhat.com>,
        "linux-kernel" <linux-kernel@vger.kernel.org>,
        "llvm" <llvm@lists.linux.dev>,
        "linux-hardening" <linux-hardening@vger.kernel.org>
Message-ID: <18ac26bcc00.365acdab160974.4357076391181710171@siddh.me>
In-Reply-To: <20230922175407.work.754-kees@kernel.org>
References: <20230922175407.work.754-kees@kernel.org>
Subject: Re: [PATCH] watch_queue: Annotate struct watch_filter with
 __counted_by
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On Fri, 22 Sep 2023 23:24:08 +0530, Kees Cook wrote:
> 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@redhat.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Siddh Raman Pant <code@siddh.me>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: Qian Cai <cai@redhat.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Tested with keyutils testsuite.

Tested-by: Siddh Raman Pant <code@siddh.me>

Thanks,
Siddh

> ---
>  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