From 3f30b158eba5c604b6e0870027eef5d19fc9271d Mon Sep 17 00:00:00 2001 From: Dean Jenkins Date: Fri, 2 Oct 2015 14:29:07 +0100 Subject: [PATCH] asix: On RX avoid creating bad Ethernet frames When RX Ethernet frames span multiple URB socket buffers, the data stream may suffer a discontinuity which will cause the current Ethernet frame in the netdev socket buffer to be incomplete. This frame needs to be discarded instead of appending unrelated data from the current URB socket buffer to the Ethernet frame in the netdev socket buffer. This avoids creating a corrupted Ethernet frame in the netdev socket buffer. A discontinuity can occur when the previous URB socket buffer held an incomplete Ethernet frame due to truncation or a URB socket buffer containing the end of the Ethernet frame was missing. Therefore, add a sanity test for when an Ethernet frame spans multiple URB socket buffers to check that the remaining bytes of the currently received Ethernet frame point to a good Data header 32-bit word of the next Ethernet frame. Upon error, reset the remaining bytes variable to zero and discard the current netdev socket buffer. Assume that the Data header is located at the start of the current socket buffer and attempt to process the next Ethernet frame from there. This avoids unnecessarily discarding a good URB socket buffer that contains a new Ethernet frame. Signed-off-by: Dean Jenkins Signed-off-by: Mark Craske Signed-off-by: David S. Miller --- drivers/net/usb/asix_common.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c index 6a8eddfea229..1e4768debcc9 100644 --- a/drivers/net/usb/asix_common.c +++ b/drivers/net/usb/asix_common.c @@ -56,6 +56,34 @@ int asix_rx_fixup_internal(struct usbnet *dev, struct sk_buff *skb, int offset = 0; u16 size; + /* When an Ethernet frame spans multiple URB socket buffers, + * do a sanity test for the Data header synchronisation. + * Attempt to detect the situation of the previous socket buffer having + * been truncated or a socket buffer was missing. These situations + * cause a discontinuity in the data stream and therefore need to avoid + * appending bad data to the end of the current netdev socket buffer. + * Also avoid unnecessarily discarding a good current netdev socket + * buffer. + */ + if (rx->remaining && (rx->remaining + sizeof(u32) <= skb->len)) { + offset = ((rx->remaining + 1) & 0xfffe) + sizeof(u32); + rx->header = get_unaligned_le32(skb->data + offset); + offset = 0; + + size = (u16)(rx->header & 0x7ff); + if (size != ((~rx->header >> 16) & 0x7ff)) { + netdev_err(dev->net, "asix_rx_fixup() Data Header synchronisation was lost, remaining %d\n", + rx->remaining); + kfree_skb(rx->ax_skb); + rx->ax_skb = NULL; + /* Discard the incomplete netdev Ethernet frame and + * assume the Data header is at the start of the current + * URB socket buffer. + */ + rx->remaining = 0; + } + } + while (offset + sizeof(u16) <= skb->len) { u16 copy_length; unsigned char *data; -- 2.30.2