From c5060cec6ba27ad3f0e7facfdf05d2f18e3e3010 Mon Sep 17 00:00:00 2001 From: "holger@eitzenberger.org" Date: Fri, 3 May 2013 00:02:20 +0000 Subject: [PATCH] asix: fix BUG in receive path when lowering MTU There is bug in the receive path of the asix driver at the time a packet is received larger than MTU size and DF bit set: BUG: unable to handle kernel paging request at 0000004000000001 IP: [] skb_release_head_state+0x2d/0xd2 ... Call Trace: [] ? skb_release_all+0x9/0x1e [] ? __kfree_skb+0x9/0x6f [] ? asix_rx_fixup_internal+0xff/0x1ae [asix] [] ? usbnet_bh+0x4f/0x226 [usbnet] ... It is easily reproducable by setting an MTU of 512 e. g. and sending something like ping -s 1472 -c 1 -M do $SELF from another box. And this is because the rx->ax_skb is freed on error, but rx->ax_skb is not reset, and the size is not reset to zero in this case. And since the skb is added again to the usbnet->done skb queue it is accessing already freed memory, resulting in the BUG when freeing a 2nd time. I therefore think the value 0x0000004000000001 show in the trace is more or less random data. Signed-off-by: Holger Eitzenberger Signed-off-by: David S. Miller --- drivers/net/usb/asix_common.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c index f7f623a5390e..577c72d5f369 100644 --- a/drivers/net/usb/asix_common.c +++ b/drivers/net/usb/asix_common.c @@ -100,6 +100,9 @@ int asix_rx_fixup_internal(struct usbnet *dev, struct sk_buff *skb, netdev_err(dev->net, "asix_rx_fixup() Bad RX Length %d\n", rx->size); kfree_skb(rx->ax_skb); + rx->ax_skb = NULL; + rx->size = 0U; + return 0; } -- 2.20.1