linux-kernel - Re: [PATCH 6/6] wifi: ath10k: remove duplicate memset() in 10.4 TDLS peer update

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Message-ID: <202312131136.5C46279@keescook>
Date:   Wed, 13 Dec 2023 11:37:10 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jeff Johnson <quic_jjohnson@...cinc.com>
Cc:     Kalle Valo <kvalo@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] wifi: ath10k: remove duplicate memset() in 10.4 TDLS
 peer update

On Wed, Dec 13, 2023 at 11:36:08AM -0800, Jeff Johnson wrote:
> On 12/13/2023 11:16 AM, Kees Cook wrote:
> > On Wed, Dec 13, 2023 at 09:06:44AM -0800, Jeff Johnson wrote:
> >> In [1] it was identified that in ath10k_wmi_10_4_gen_tdls_peer_update()
> >> the memset(skb->data, 0, sizeof(*cmd)) is unnecessary since function
> >> ath10k_wmi_alloc_skb() already zeroes skb->data, so remove it.
> > 
> > Is .gen_tdls_peer_update only ever called after a fresh allocation? It
> > wasn't obvious to me as I tried to follow the call paths. Is there harm
> > in leaving this?
> 
> The only harm is a slight increase in code size and cpu cycles.
> 
> However note the skb allocation is done within
> ath10k_wmi_10_4_gen_tdls_peer_update() itself, just before the code
> being removed:
> 	skb = ath10k_wmi_alloc_skb(ar, len);
> 	if (!skb)
> 		return ERR_PTR(-ENOMEM);
> 
> And in ath10k_wmi_alloc_skb() we have:
> 	memset(skb->data, 0, round_len);
> 
> So the memset() being removed is always redundant.

LOL. I see now. I missed that was was looking outside the function! :P

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

-- 
Kees Cook