From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH] net: Work around crash in ipv6 fib-walk-continue Date: Fri, 4 May 2018 11:47:43 -0600 Message-ID: <513868fb-b548-0312-a276-482fed070d0f@gmail.com> References: <1524160886-20401-1-git-send-email-greearb@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit To: greearb@candelatech.com, netdev@vger.kernel.org Return-path: Received: from mail-pf0-f196.google.com ([209.85.192.196]:46667 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751390AbeEDRrq (ORCPT ); Fri, 4 May 2018 13:47:46 -0400 Received: by mail-pf0-f196.google.com with SMTP id p12so17967988pff.13 for ; Fri, 04 May 2018 10:47:46 -0700 (PDT) In-Reply-To: <1524160886-20401-1-git-send-email-greearb@candelatech.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 4/19/18 12:01 PM, greearb@candelatech.com wrote: > From: Ben Greear > > This keeps us from crashing in certain test cases where we > bring up many (1000, for instance) mac-vlans with IPv6 > enabled in the kernel. This bug has been around for a > very long time. > > Until a real fix is found (and for stable), maybe it > is better to return an incomplete fib walk instead > of crashing. > > BUG: unable to handle kernel NULL pointer dereference at 8 > IP: fib6_walk_continue+0x5b/0x140 [ipv6] > PGD 80000007dfc0c067 P4D 80000007dfc0c067 PUD 7e66ff067 PMD 0 > Oops: 0000 [#1] PREEMPT SMP PTI > Modules linked in: nf_conntrack_netlink nf_conntrack nfnetlink nf_defrag_ipv4 libcrc32c vrf] > CPU: 3 PID: 15117 Comm: ip Tainted: G O 4.16.0+ #5 > Hardware name: Iron_Systems,Inc CS-CAD-2U-A02/X10SRL-F, BIOS 2.0b 05/02/2017 > RIP: 0010:fib6_walk_continue+0x5b/0x140 [ipv6] > RSP: 0018:ffffc90008c3bc10 EFLAGS: 00010287 > RAX: ffff88085ac45050 RBX: ffff8807e03008a0 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: ffffc90008c3bc48 RDI: ffffffff8232b240 > RBP: ffff880819167600 R08: 0000000000000008 R09: ffff8807dff10071 > R10: ffffc90008c3bbd0 R11: 0000000000000000 R12: ffff8807e03008a0 > R13: 0000000000000002 R14: ffff8807e05744c8 R15: ffff8807e08ef000 > FS: 00007f2f04342700(0000) GS:ffff88087fcc0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000008 CR3: 00000007e0556002 CR4: 00000000003606e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > inet6_dump_fib+0x14b/0x2c0 [ipv6] > netlink_dump+0x216/0x2a0 > netlink_recvmsg+0x254/0x400 > ? copy_msghdr_from_user+0xb5/0x110 > ___sys_recvmsg+0xe9/0x230 > ? find_held_lock+0x3b/0xb0 > ? __handle_mm_fault+0x617/0x1180 > ? __audit_syscall_entry+0xb3/0x110 > ? __sys_recvmsg+0x39/0x70 > __sys_recvmsg+0x39/0x70 > do_syscall_64+0x63/0x120 > entry_SYSCALL_64_after_hwframe+0x3d/0xa2 > RIP: 0033:0x7f2f03a72030 > RSP: 002b:00007fffab3de508 EFLAGS: 00000246 ORIG_RAX: 000000000000002f > RAX: ffffffffffffffda RBX: 00007fffab3e641c RCX: 00007f2f03a72030 > RDX: 0000000000000000 RSI: 00007fffab3de570 RDI: 0000000000000004 > RBP: 0000000000000000 R08: 0000000000007e6c R09: 00007fffab3e63a8 > R10: 00007fffab3de5b0 R11: 0000000000000246 R12: 00007fffab3e6608 > R13: 000000000066b460 R14: 0000000000007e6c R15: 0000000000000000 > Code: 85 d2 74 17 f6 40 2a 04 74 11 8b 53 2c 85 d2 0f 84 d7 00 00 00 83 ea 01 89 53 2c c7 4 > RIP: fib6_walk_continue+0x5b/0x140 [ipv6] RSP: ffffc90008c3bc10 > CR2: 0000000000000008 > ---[ end trace bd03458864eb266c ]--- > > Signed-off-by: Ben Greear > --- > Does your use case that triggers this involve replacing routes? I just noticed the route delete code in fib6_add_rt2node does not have the 'Adjust walkers' code that is in fib6_del_route. Further, the adjust walkers code in fib6_del_route looks suspicious in its timing with route deletes. If you have a reliable reproducer we can try a few things with fib6_del_route and the walker code.