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

Sasha Levin
2022-04-12T01:11:33Z

From: Marcin Kozlowski <marcinguy@gmail.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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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