linux-hardening - Re: [PATCH] ALSA: usx2y: Annotate struct snd_usx2y_urb_seq with __counted

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Date: Sat, 23 Sep 2023 10:30:48 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Kees Cook <keescook@...omium.org>, Jaroslav Kysela <perex@...ex.cz>
Cc: Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.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] ALSA: usx2y: Annotate struct snd_usx2y_urb_seq with
 __counted_by



On 9/22/23 11:50, 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 snd_usx2y_urb_seq.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Jaroslav Kysela <perex@...ex.cz>
> Cc: Takashi Iwai <tiwai@...e.com>
> Cc: alsa-devel@...a-project.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

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

Thanks
-- 
Gustavo

> ---
>   sound/usb/usx2y/usbusx2y.h      | 2 +-
>   sound/usb/usx2y/usbusx2yaudio.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/usb/usx2y/usbusx2y.h b/sound/usb/usx2y/usbusx2y.h
> index 8d82f5cc2fe1..391fd7b4ed5e 100644
> --- a/sound/usb/usx2y/usbusx2y.h
> +++ b/sound/usb/usx2y/usbusx2y.h
> @@ -18,7 +18,7 @@ struct snd_usx2y_async_seq {
>   struct snd_usx2y_urb_seq {
>   	int	submitted;
>   	int	len;
> -	struct urb	*urb[];
> +	struct urb	*urb[] __counted_by(len);
>   };
>   
>   #include "usx2yhwdeppcm.h"
> diff --git a/sound/usb/usx2y/usbusx2yaudio.c b/sound/usb/usx2y/usbusx2yaudio.c
> index 5197599e7aa6..ca7888495a9f 100644
> --- a/sound/usb/usx2y/usbusx2yaudio.c
> +++ b/sound/usb/usx2y/usbusx2yaudio.c
> @@ -681,6 +681,7 @@ static int usx2y_rate_set(struct usx2ydev *usx2y, int rate)
>   			err = -ENOMEM;
>   			goto cleanup;
>   		}
> +		us->len = NOOF_SETRATE_URBS;
>   		usbdata = kmalloc_array(NOOF_SETRATE_URBS, sizeof(int),
>   					GFP_KERNEL);
>   		if (!usbdata) {
> @@ -702,7 +703,6 @@ static int usx2y_rate_set(struct usx2ydev *usx2y, int rate)
>   		if (err < 0)
>   			goto cleanup;
>   		us->submitted =	0;
> -		us->len =	NOOF_SETRATE_URBS;
>   		usx2y->us04 =	us;
>   		wait_event_timeout(usx2y->in04_wait_queue, !us->len, HZ);
>   		usx2y->us04 =	NULL;