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

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

[Phillip Potter]

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: syzbot+e4534e8c1c382508312c@syzkaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
---
 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;
 
 	htc_hdr = (struct htc_frame_hdr *) skb->data;
-- 
2.30.2

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

[Florian Westphal]

Phillip Potter <phil@philpotter.co.uk> 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: syzbot+e4534e8c1c382508312c@syzkaller.appspotmail.com
> Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
> ---
>  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.

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

[Phillip Potter]

On Sun, May 02, 2021 at 10:28:27PM +0200, Florian Westphal wrote:
> Phillip Potter <phil@philpotter.co.uk> 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: syzbot+e4534e8c1c382508312c@syzkaller.appspotmail.com
> > Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
> > ---
> >  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