From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: Re: v4.14-rc2/arm64 kernel BUG at net/core/skbuff.c:2626 Date: Mon, 2 Oct 2017 18:34:02 +0100 Message-ID: <20171002173401.GA3456@leverpostej> References: <20171002104947.GE20737@leverpostej> <20171002142156.GB21696@leverpostej> <1506955708.8061.5.camel@edumazet-glaptop3.roam.corp.google.com> <20171002172131.GA3360@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Dumazet , LKML , netdev , linux-arm-kernel@lists.infradead.org, syzkaller , "David S. Miller" , Willem de Bruijn To: Eric Dumazet Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Oct 02, 2017 at 10:27:15AM -0700, Eric Dumazet wrote: > On Mon, Oct 2, 2017 at 10:21 AM, Mark Rutland wrote: > > On Mon, Oct 02, 2017 at 07:48:28AM -0700, Eric Dumazet wrote: > >> Please try the following fool proof patch. > >> > >> This is what I had in my local tree back in August but could not > >> conclude on the syzkaller bug I was working on. > >> > >> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c > >> index 681e33998e03b609fdca83a83e0fc62a3fee8c39..e51d777797a927058760a1ab7af00579f7488cb5 100644 > >> --- a/net/ipv4/icmp.c > >> +++ b/net/ipv4/icmp.c > >> @@ -732,7 +732,8 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) > >> room = 576; > >> room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; > >> room -= sizeof(struct icmphdr); > >> - > >> + if (room < 0) > >> + goto ende; > >> icmp_param.data_len = skb_in->len - icmp_param.offset; > >> if (icmp_param.data_len > room) > >> icmp_param.data_len = room; > >> > > > > Unfortuantely, with this applied I still see the issue. > > > > Syzkaller came up with a minimized reproducer [1], which can trigger the > > issue near instantly under syz-execprog. If there's anything that would > > help to narrow this down, I'm more than happy to give it a go. > > > > Thanks, > > Mark. > > > > [1] https://www.kernel.org/pub/linux/kernel/people/mark/bugs/20171002-skb_clone-misaligned-atomic/syzkaller.repro > > Note that I was not trying to address the misaligned stuff. Aargh, I put the reproducer in the wrong folder thanks to tab-completing my kup command. :/ The reproducer linked above is for the kernel BUG at net/core/skbuff.c:2626. I've uploaded a copy into the relevant bug directory [1], but that'll take a little while to sync out. I'll drop it from the misalignment bug folder once that's visible to all. Sorry about that! Thanks, Mark. [1] https://www.kernel.org/pub/linux/kernel/people/mark/bugs/20171002-skbuff-bug/