Re: [PATCH v2] ath9k: ath9k_htc_rx_msg: return when sk_buff is too small
From: Kalle Valo <hidden>
Date: 2021-05-30 09:01:32
Also in:
linux-wireless, lkml
Phillip Potter [off-list ref] writes:
quoted hunk
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; + }
This does not look complete to me, I think the function is missing
proper length checks. For example, with ENDPOINT0 it reads two byte
msg_id after the htc header and it's not verified that skb really has
that. I did not check if ep_callbacks.rx handlers have proper length
handling, I recommend verifying that also while fixing this.
Also I want to point out that the skb is freed differently based on
endpoint, I did not check why and don't know if it causes:
if (epid < 0 || epid >= ENDPOINT_MAX) {
if (pipe_id != USB_REG_IN_PIPE)
dev_kfree_skb_any(skb);
else
kfree_skb(skb);
return;
}
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