From: David Ahern <dsahern@gmail.com>
To: greearb@candelatech.com, netdev@vger.kernel.org
Subject: Re: [PATCH] net: Work around crash in ipv6 fib-walk-continue
Date: Fri, 4 May 2018 11:47:43 -0600 [thread overview]
Message-ID: <513868fb-b548-0312-a276-482fed070d0f@gmail.com> (raw)
In-Reply-To: <1524160886-20401-1-git-send-email-greearb@candelatech.com>
On 4/19/18 12:01 PM, greearb@candelatech.com wrote:
> From: Ben Greear <greearb@candelatech.com>
>
> 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 <greearb@candelatech.com>
> ---
>
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.
next prev parent reply other threads:[~2018-05-04 17:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-19 18:01 [PATCH] net: Work around crash in ipv6 fib-walk-continue greearb
2018-05-04 17:47 ` David Ahern [this message]
2018-05-04 17:57 ` Ben Greear
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