From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] net: fec: fix regression on i.MX28 introduced by rx_copybreak support Date: Tue, 07 Oct 2014 13:15:07 -0400 (EDT) Message-ID: <20141007.131507.635415594538460008.davem@davemloft.net> References: <1412687977-11742-1-git-send-email-LW@KARO-electronics.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org, rmk+kernel@arm.linux.org.uk, Frank.Li@freescale.com, fabio.estevam@freescale.com, linux-kernel@vger.kernel.org To: LW@KARO-electronics.de Return-path: In-Reply-To: <1412687977-11742-1-git-send-email-LW@KARO-electronics.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org =46rom: Lothar Wa=DFmann Date: Tue, 7 Oct 2014 15:19:37 +0200 > commit 1b7bde6d659d ("net: fec: implement rx_copybreak to improve rx = performance") > introduced a regression for i.MX28. The swap_buffer() function doing > the endian conversion of the received data on i.MX28 may access memor= y > beyond the actual packet size in the DMA buffer. fec_enet_copybreak() > does not copy those bytes, so that the last bytes of a packet may be > filled with invalid data after swapping. > This will likely lead to checksum errors on received packets. > E.g. when trying to mount an NFS rootfs: > UDP: bad checksum. From 192.168.1.225:111 to 192.168.100.73:44662 ule= n 36 >=20 > Do the byte swapping and copying to the new skb in one go if > necessary. >=20 > Signed-off-by: Lothar Wa=DFmann Why don't you just round up the length fec_enet_copybreak() uses when need_swap is true? Then you will end up mimicking the original behavio= r and not require this new helper function. And in any case I agree with Sergei that if you do retain your approach= , the new 'swap' argument to fec_enet_copybreak() should be a 'bool'. I'm really surprised there isn't a control register bit to adjust the endianness of the data DMA'd to/from the network.