linux-kernel - Re: [PATCH][next] media: usb: siano: Fix undefined behavior bug in struct smsusb_urb

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Date:   Fri, 29 Sep 2023 10:28:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] media: usb: siano: Fix undefined behavior bug in
 struct smsusb_urb_t

On Fri, Sep 29, 2023 at 05:42:11PM +0200, Gustavo A. R. Silva wrote:
> `struct urb` is a flexible structure, which means that it contains a
> flexible-array member at the bottom. This could potentially lead to an
> overwrite of the object `wq` at run-time with the contents of `urb`.
> 
> Fix this by placing object `urb` at the end of `struct smsusb_urb_t`.
> 
> Fixes: dd47fbd40e6e ("[media] smsusb: don't sleep while atomic")
> Cc: stable@...r.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

As Jann pointed out, it's unlikely there is a function bug here, but I
still think it's right to make sure this is robust and clears the way
for -Wflex-array-member-not-at-end.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook