netdev - [PATCH AUTOSEL 5.10 21/30] net: usb: aqc111: Fix out-of-bounds accesses in RX fixup

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Date:   Mon, 11 Apr 2022 20:48:55 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Marcin Kozlowski <marcinguy@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, kuba@...nel.org,
        pabeni@...hat.com, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 21/30] net: usb: aqc111: Fix out-of-bounds accesses in RX fixup

From: Marcin Kozlowski <marcinguy@...il.com>

[ Upstream commit afb8e246527536848b9b4025b40e613edf776a9d ]

aqc111_rx_fixup() contains several out-of-bounds accesses that can be
triggered by a malicious (or defective) USB device, in particular:

 - The metadata array (desc_offset..desc_offset+2*pkt_count) can be out of bounds,
   causing OOB reads and (on big-endian systems) OOB endianness flips.
 - A packet can overlap the metadata array, causing a later OOB
   endianness flip to corrupt data used by a cloned SKB that has already
   been handed off into the network stack.
 - A packet SKB can be constructed whose tail is far beyond its end,
   causing out-of-bounds heap data to be considered part of the SKB's
   data.

Found doing variant analysis. Tested it with another driver (ax88179_178a), since
I don't have a aqc111 device to test it, but the code looks very similar.

Signed-off-by: Marcin Kozlowski <marcinguy@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/usb/aqc111.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/aqc111.c b/drivers/net/usb/aqc111.c
index 0717c18015c9..c9c409518174 100644
--- a/drivers/net/usb/aqc111.c
+++ b/drivers/net/usb/aqc111.c
@@ -1102,10 +1102,15 @@ static int aqc111_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 	if (start_of_descs != desc_offset)
 		goto err;
 
-	/* self check desc_offset from header*/
-	if (desc_offset >= skb_len)
+	/* self check desc_offset from header and make sure that the
+	 * bounds of the metadata array are inside the SKB
+	 */
+	if (pkt_count * 2 + desc_offset >= skb_len)
 		goto err;
 
+	/* Packets must not overlap the metadata array */
+	skb_trim(skb, desc_offset);
+
 	if (pkt_count == 0)
 		goto err;
 
-- 
2.35.1