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

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

Phillip Potter [off-list ref] wrote:

This leaks the skb.

On Sun, May 02, 2021 at 10:28:27PM +0200, Florian Westphal wrote:

Phillip Potter [off-list ref] wrote:

quoted

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