Hi Yuiry, Thanks for the patch. Changes look good to me. Thanks, -Raghu
> -----Original Message----- > From: Yuriy M. Kaminskiy <yum...@gmail.com> > Sent: Monday, January 21, 2019 6:18 PM > To: netdev@vger.kernel.org > Cc: Woojung Huh - C21699 <woojung....@microchip.com>; > UNGLinuxDriver <unglinuxdri...@microchip.com> > Subject: [PATCH] lan78xx: fix ip header misalignment > > lan78xx.c:rx_submit() allocates space for frame-to-be-received with > netdev_alloc_skb_ip_align(), which misalign start of buffer by 2 bytes in > expectation that frame will start from 14-byte ethernet header, then ip > header; if start of buffer misaligned by 2 bytes, ip header will be 16-byte > aligned. > > Unfortunately, usb frame that is sent by lan78xx starts with another 10-byte > header (lan78xx_rx(): rx_cmd_a/rx_cmd_b/rx_cmd_c), *then* follows > ethernet header, and *then* ip header (which ends up being misaligned). > > This issue was observed on arm platform (where misaligned 32-bit word > access triggers exception and leaves traces in /proc/cpu/alignment, see > https://github.com/raspberrypi/linux/issues/2599 ; for me, about any > ipv6 traffic that hits machine - `ping -I eth0 ip6-allnodes`, tcp/udp > packets, etc > triggered increase in this counter, with ip6_datagram_recv_common_ctl, > icmpv6_echo_reply, etc as culprit). > > If we just allocate skb data without any misalignment tricks, ip header will > end up and at offset 24 (8-byte aligned). > > Patch attached; runtime-tested with raspbian fork of stable/4.14.y [4.14.92] > on Raspberry pi 3B+ (it is slightly different from mainline, but patch should > not have any conflicts, all affected code is pretty same). > > P.S. I'm not subscribed, please CC me on reply.
