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From:   Phillip Potter <phil@philpotter.co.uk>
To:     kvalo@codeaurora.org
Cc:     davem@davemloft.net, kuba@kernel.org,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, ath9k-devel@qca.qualcomm.com,
        fw@strlen.de
Subject: [PATCH v2] ath9k: ath9k_htc_rx_msg: return when sk_buff is too small
Date:   Sun,  2 May 2021 22:26:11 +0100
Message-Id: <20210502212611.1818-1-phil@philpotter.co.uk>
MIME-Version: 1.0
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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 if not,
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>
---

V2:
* Free skb properly when this problem is detected, as pointed out by
  Florian Westphal.

---
 drivers/net/wireless/ath/ath9k/htc_hst.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/htc_hst.c b/drivers/net/wireless/ath/ath9k/htc_hst.c
index 510e61e97dbc..1fe89b068ac4 100644
--- a/drivers/net/wireless/ath/ath9k/htc_hst.c
+++ b/drivers/net/wireless/ath/ath9k/htc_hst.c
@@ -406,6 +406,11 @@ void ath9k_htc_rx_msg(struct htc_target *htc_handle,
 	if (!htc_handle || !skb)
 		return;
 
+	if (!pskb_may_pull(skb, sizeof(struct htc_frame_hdr))) {
+		kfree_skb(skb);
+		return;
+	}
+
 	htc_hdr = (struct htc_frame_hdr *) skb->data;
 	epid = htc_hdr->endpoint_id;
 
-- 
2.30.2