Subject: Re: [PATCH] ath9k: ath9k_htc_rx_msg: return when sk_buff is too small

From: Phillip Potter <[email-masked]>
Date: Sun, 2 May 2021 21:47:34 +0100

On Sun, May 02, 2021 at 10:28:27PM +0200, Florian Westphal wrote:
> Phillip Potter <[email-masked]> wrote:
> > At the start of ath9k_htc_rx_msg, we check to see if the skb pointer is
> > valid, but what we don't do is check if it is large enough to contain a
> > valid struct htc_frame_hdr. We should check for this and return, as the
> > buffer is invalid in this case. Fixes a KMSAN-found uninit-value bug
> > reported by syzbot at:
> > https://syzkaller.appspot.com/bug?id=7dccb7d9ad4251df1c49f370607a49e1f09644ee
> > 
> > Reported-by: [email-masked]
> > Signed-off-by: Phillip Potter <[email-masked]>
> > ---
> >  drivers/net/wireless/ath/ath9k/htc_hst.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/wireless/ath/ath9k/htc_hst.c b/drivers/net/wireless/ath/ath9k/htc_hst.c
> > index 510e61e97dbc..9dbfff7a388e 100644
> > --- a/drivers/net/wireless/ath/ath9k/htc_hst.c
> > +++ b/drivers/net/wireless/ath/ath9k/htc_hst.c
> > @@ -403,7 +403,7 @@ void ath9k_htc_rx_msg(struct htc_target *htc_handle,
> >  	struct htc_endpoint *endpoint;
> >  	__be16 *msg_id;
> >  
> > -	if (!htc_handle || !skb)
> > +	if (!htc_handle || !skb || !pskb_may_pull(skb, sizeof(struct htc_frame_hdr)))
> >  		return;
> 
> This leaks the skb.

Dear Florian,

Thank you, and apologies, I shall resend. Not sure how I missed that.

Regards,
Phil