linux-hardening - Re: [PATCH] virtio_console: Annotate struct port_buffer with __counted

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Date: Mon, 25 Sep 2023 13:24:19 +0200
From: Amit Shah <amit@...radead.org>
To: Kees Cook <keescook@...omium.org>, Amit Shah <amit@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman
	 <gregkh@...uxfoundation.org>, virtualization@...ts.linux-foundation.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] virtio_console: Annotate struct port_buffer with
 __counted_by

On Fri, 2023-09-22 at 10:51 -0700, 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 port_buffer.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Amit Shah <amit@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: virtualization@...ts.linux-foundation.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/char/virtio_console.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 680d1ef2a217..431e9e5bf9c1 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -106,7 +106,7 @@ struct port_buffer {
>  	unsigned int sgpages;
>  
>  	/* sg is used if spages > 0. sg must be the last in is struct */
> -	struct scatterlist sg[];
> +	struct scatterlist sg[] __counted_by(sgpages);
>  };

Reviewed-by: Amit Shah <amit@...nel.org>

Greg, please pick this up.

Thanks,

		Amit