linux-hardening - Re: [PATCH v2] tty: rfcomm: prefer struct

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Date: Mon, 13 May 2024 07:07:31 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Erick Archer <erick.archer@...look.com>,
 Marcel Holtmann <marcel@...tmann.org>,
 Johan Hedberg <johan.hedberg@...il.com>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Kees Cook <keescook@...omium.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
 llvm@...ts.linux.dev
Subject: Re: [PATCH v2] tty: rfcomm: prefer struct_size over open coded
 arithmetic

On 12. 05. 24, 13:17, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1][2].
> 
> As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
> this structure ends in a flexible array:
...
> --- a/include/net/bluetooth/rfcomm.h
> +++ b/include/net/bluetooth/rfcomm.h
...
> @@ -528,12 +527,12 @@ static int rfcomm_get_dev_list(void __user *arg)
>   	list_for_each_entry(dev, &rfcomm_dev_list, list) {
>   		if (!tty_port_get(&dev->port))
>   			continue;
> -		(di + n)->id      = dev->id;
> -		(di + n)->flags   = dev->flags;
> -		(di + n)->state   = dev->dlc->state;
> -		(di + n)->channel = dev->channel;
> -		bacpy(&(di + n)->src, &dev->src);
> -		bacpy(&(di + n)->dst, &dev->dst);
> +		di[n].id      = dev->id;
> +		di[n].flags   = dev->flags;
> +		di[n].state   = dev->dlc->state;
> +		di[n].channel = dev->channel;
> +		bacpy(&di[n].src, &dev->src);
> +		bacpy(&di[n].dst, &dev->dst);

This does not relate much to "prefer struct_size over open coded 
arithmetic". It should have been in a separate patch.

Other than that, LGTM.

thanks,
-- 
js
suse labs