[PATCH] net: usb: sr9700: validate receive packet extent

[Pengpeng Hou]

sr9700_rx_fixup() copies len bytes from skb->data + SR_RX_OVERHEAD when
a URB contains multiple packets. The old check compared len against
skb->len, but the source pointer has already skipped SR_RX_OVERHEAD
bytes.

Validate len against the remaining bytes after SR_RX_OVERHEAD before the
copy and cursor advance.

Signed-off-by: Pengpeng Hou <pengpeng@xxxxxxxxxxx>
---
diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -355,7 +355,8 @@
 		/* ignore the CRC length */
 		len = (skb->data[1] | (skb->data[2] << 8)) - 4;
 
-		if (len > ETH_FRAME_LEN || len > skb->len || len < 0)
+		if (len > ETH_FRAME_LEN || len < 0 ||
+		    len > skb->len - SR_RX_OVERHEAD)
 			return 0;
 
 		/* the last packet of current skb */