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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Qiujun Huang <hqjagain@gmail.com>
Cc:     ath9k-devel@qca.qualcomm.com, davem@davemloft.net,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, anenbupt@gmail.com
Subject: Re: [PATCH] ath9k: fix stack-out-of-bounds Write in ath9k_hif_usb_rx_cb
References: <1585625296-31013-1-git-send-email-hqjagain@gmail.com>
Date:   Tue, 31 Mar 2020 14:03:22 +0300
In-Reply-To: <1585625296-31013-1-git-send-email-hqjagain@gmail.com> (Qiujun
        Huang's message of "Tue, 31 Mar 2020 11:28:16 +0800")
Message-ID: <87bloc23d1.fsf@kamboji.qca.qualcomm.com>
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Qiujun Huang <hqjagain@gmail.com> writes:

> Add barrier to accessing the stack array skb_pool.
>
> Reported-by: syzbot+d403396d4df67ad0bd5f@syzkaller.appspotmail.com
> Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
> ---
>  drivers/net/wireless/ath/ath9k/hif_usb.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
> index dd0c323..c4a2b72 100644
> --- a/drivers/net/wireless/ath/ath9k/hif_usb.c
> +++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
> @@ -612,6 +612,11 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
>  			hif_dev->remain_skb = nskb;
>  			spin_unlock(&hif_dev->rx_lock);
>  		} else {
> +			if (pool_index == MAX_PKT_NUM_IN_TRANSFER) {
> +				dev_err(&hif_dev->udev->dev,
> +					"ath9k_htc: over RX MAX_PKT_NUM\n");
> +				goto err;
> +			}

What about 'pool_index >= MAX_PKT_NUM_IN_TRANSFER' just to be on the
safe side? Ah, but then error handling won't work:

err:
	for (i = 0; i < pool_index; i++) {
		RX_STAT_ADD(skb_completed_bytes, skb_pool[i]->len);
		ath9k_htc_rx_msg(hif_dev->htc_handle, skb_pool[i],
				 skb_pool[i]->len, USB_WLAN_RX_PIPE);
		RX_STAT_INC(skb_completed);
	}

Maybe that should use 'min(pool_index, MAX_PKT_NUM_IN_TRANSFER - 1)' or
something? Or maybe it's just overengineerin, dunno.

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches