From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: AW: PROBLEM: Kernel Oops in UDP stack Date: Thu, 2 Aug 2018 06:13:02 -0700 Message-ID: <405319c1-2fa0-e1b5-7173-b19d9769d98a@gmail.com> References: <18092446dfa7435aaa8deaab65afbf23@ZCOM03.mut-group.com> <96753ca4-88fe-aa26-b439-6e22eaf8b524@gmail.com> <9f9d731107594b368504cbbaf698bc3d@ZCOM03.mut-group.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "'netdev@vger.kernel.org'" , "'linux-kernel@vger.kernel.org'" , Matthias Wystrik To: David Laight , 'Marcel Hellwig' , 'Eric Dumazet' , "'davem@davemloft.net'" , "'kuznet@ms2.inr.ac.ru'" , "'yoshfuji@linux-ipv6.org'" , "'andrew@lunn.ch'" Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 08/02/2018 02:17 AM, David Laight wrote: > From: Marcel Hellwig >> Sent: 01 August 2018 11:36 >>>> [] (udp_recvmsg+0x284/0x33c) from [] (inet_recvmsg+0x38/0x4c): >> net/ipv4/udp.c:1234 >>> >>> sin->sin_addr.s_addr = ip_hdr(skb)->saddr; >>> >>> Unaligned access trap (virtual address c14fe63a), so either sin or ip_hdr(skb) are not on a 32bit >> alignment >>> >>> Can you produce the disassembly of the trapping instruction ? >> >> https://gist.github.com/hellow554/6b11c6c0827d5db80a7e66f71f5636ff#file-net_uipv4_udp-lst-L1892-L1895 >> >> sin->sin_addr.s_addr = ip_hdr(skb)->saddr; >> c0228ad8: e5943080 ldr r3, [r4, #128] ; 0x80 >> c0228adc: e593300c ldr r3, [r3, #12] >> c0228ae0: e5823004 str r3, [r2, #4] > > There are actually 2 faults, difficult to quickly sort out the merged tracebacks. > You are also running a rather old kernel: Linux version 3.4.113. > > It may well be that whichever ethernet driver generated the misaligned frame > has since been fixed. A misalign frame driver problem would have faulted earlier in IP stack, much before we perform the copy to user space in udp_recvmsg()