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From:   Szymon Heidrich <szymon.heidrich@gmail.com>
To:     davem@davemloft.net, edumazet@google.com
Cc:     kuba@kernel.org, pabeni@redhat.com, szymon.heidrich@gmail.com,
        linux-usb@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] net: usb: sr9700: Handle negative len
Date:   Sat, 14 Jan 2023 19:23:26 +0100
Message-Id: <20230114182326.30479-1-szymon.heidrich@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Packet len computed as difference of length word extracted from
skb data and four may result in a negative value. In such case
processing of the buffer should be interrupted rather than
setting sr_skb->len to an unexpectedly large value (due to cast
from signed to unsigned integer) and passing sr_skb to
usbnet_skb_return.

Fixes: e9da0b56fe27 ("sr9700: sanity check for packet length")
Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
---
 drivers/net/usb/sr9700.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
index 5a53e63d3..3164451e1 100644
--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -413,7 +413,7 @@ static int sr9700_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 		/* ignore the CRC length */
 		len = (skb->data[1] | (skb->data[2] << 8)) - 4;
 
-		if (len > ETH_FRAME_LEN || len > skb->len)
+		if (len > ETH_FRAME_LEN || len > skb->len || len < 0)
 			return 0;
 
 		/* the last packet of current skb */
-- 
2.39.0