From ecf7cf8efb59789e2b21d2f9ab926142579092b2 Mon Sep 17 00:00:00 2001
From: Szymon Heidrich <szymon.heidrich@gmail.com>
Date: Sat, 14 Jan 2023 19:23:26 +0100
Subject: [PATCH] net: usb: sr9700: Handle negative len
Git-commit: ecf7cf8efb59789e2b21d2f9ab926142579092b2
Patch-mainline: v6.2-rc5
References: git-fixes

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>
Link: https://lore.kernel.org/r/20230114182326.30479-1-szymon.heidrich@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Oliver Neukum <oneukum@suse.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 5a53e63d33a6..3164451e1010 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 */
-- 
2.35.3