linux-hardening - Re: [PATCH] afs: Annotate struct afs_permits with __counted

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Message-ID: <57b92e94-b9a6-c56f-0812-aa54d15e0c7d@embeddedor.com>
Date:   Fri, 15 Sep 2023 14:51:01 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>,
        David Howells <dhowells@...hat.com>
Cc:     Marc Dionne <marc.dionne@...istor.com>,
        linux-afs@...ts.infradead.org,
        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: Re: [PATCH] afs: Annotate struct afs_permits with __counted_by



On 9/15/23 14:14, 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 afs_permits.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: David Howells <dhowells@...hat.com>
> Cc: Marc Dionne <marc.dionne@...istor.com>
> Cc: linux-afs@...ts.infradead.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
-- 
Gustavo

> ---
>   fs/afs/internal.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/afs/internal.h b/fs/afs/internal.h
> index 07433a5349ca..469a717467a4 100644
> --- a/fs/afs/internal.h
> +++ b/fs/afs/internal.h
> @@ -705,7 +705,7 @@ struct afs_permits {
>   	refcount_t		usage;
>   	unsigned short		nr_permits;	/* Number of records */
>   	bool			invalidated;	/* Invalidated due to key change */
> -	struct afs_permit	permits[];	/* List of permits sorted by key pointer */
> +	struct afs_permit	permits[] __counted_by(nr_permits);	/* List of permits sorted by key pointer */
>   };
>   
>   /*