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Date: Thu, 17 May 2018 12:32:23 -0700
From: William Tu <u9012063@...il.com>
To: Petr Machata <petrm@...lanox.com>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>,
David Miller <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Dmitry Kozlov <xeb@...l.ru>
Subject: Re: [PATCH net 1/7] net: ip6_gre: Request headroom in __gre6_xmit()
On Thu, May 17, 2018 at 7:36 AM, Petr Machata <petrm@...lanox.com> wrote:
> __gre6_xmit() pushes GRE headers before handing over to ip6_tnl_xmit()
> for generic IP-in-IP processing. However it doesn't make sure that there
> is enough headroom to push the header to. That can lead to the panic
> cited below. (Reproducer below that).
>
> Fix by requesting either needed_headroom if already primed, or just the
> bare minimum needed for the header otherwise.
>
> [ 158.576725] kernel BUG at net/core/skbuff.c:104!
> [ 158.581510] invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
> [ 158.587174] Modules linked in: act_mirred cls_matchall ip6_gre ip6_tunnel tunnel6 gre sch_ingress vrf veth x86_pkg_temp_thermal mlx_platform nfsd e1000e leds_mlxcpld
> [ 158.602268] CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 4.17.0-rc4-net_master-custom-139 #10
> [ 158.610938] Hardware name: Mellanox Technologies Ltd. "MSN2410-CB2F"/"SA000874", BIOS 4.6.5 03/08/2016
> [ 158.620426] RIP: 0010:skb_panic+0xc3/0x100
> [ 158.624586] RSP: 0018:ffff8801d3f27110 EFLAGS: 00010286
> [ 158.629882] RAX: 0000000000000082 RBX: ffff8801c02cc040 RCX: 0000000000000000
> [ 158.637127] RDX: 0000000000000082 RSI: dffffc0000000000 RDI: ffffed003a7e4e18
> [ 158.644366] RBP: ffff8801bfec8020 R08: ffffed003aabce19 R09: ffffed003aabce19
> [ 158.651574] R10: 000000000000000b R11: ffffed003aabce18 R12: ffff8801c364de66
> [ 158.658786] R13: 000000000000002c R14: 00000000000000c0 R15: ffff8801c364de68
> [ 158.666007] FS: 0000000000000000(0000) GS:ffff8801d5400000(0000) knlGS:0000000000000000
> [ 158.674212] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 158.680036] CR2: 00007f4b3702dcd0 CR3: 0000000003228002 CR4: 00000000001606e0
> [ 158.687228] Call Trace:
> [ 158.689752] ? __gre6_xmit+0x246/0xd80 [ip6_gre]
> [ 158.694475] ? __gre6_xmit+0x246/0xd80 [ip6_gre]
> [ 158.699141] skb_push+0x78/0x90
> [ 158.702344] __gre6_xmit+0x246/0xd80 [ip6_gre]
> [ 158.706872] ip6gre_tunnel_xmit+0x3bc/0x610 [ip6_gre]
> [ 158.711992] ? __gre6_xmit+0xd80/0xd80 [ip6_gre]
> [ 158.716668] ? debug_check_no_locks_freed+0x210/0x210
> [ 158.721761] ? print_irqtrace_events+0x120/0x120
> [ 158.726461] ? sched_clock_cpu+0x18/0x210
> [ 158.730572] ? sched_clock_cpu+0x18/0x210
> [ 158.734692] ? cyc2ns_read_end+0x10/0x10
> [ 158.738705] ? skb_network_protocol+0x76/0x200
> [ 158.743216] ? netif_skb_features+0x1b2/0x550
> [ 158.747648] dev_hard_start_xmit+0x137/0x770
> [ 158.752010] sch_direct_xmit+0x2ef/0x5d0
> [ 158.755992] ? pfifo_fast_dequeue+0x3fa/0x670
> [ 158.760460] ? pfifo_fast_change_tx_queue_len+0x810/0x810
> [ 158.765975] ? __lock_is_held+0xa0/0x160
> [ 158.770002] __qdisc_run+0x39e/0xfc0
> [ 158.773673] ? _raw_spin_unlock+0x29/0x40
> [ 158.777781] ? pfifo_fast_enqueue+0x24b/0x3e0
> [ 158.782191] ? sch_direct_xmit+0x5d0/0x5d0
> [ 158.786372] ? pfifo_fast_dequeue+0x670/0x670
> [ 158.790818] ? __dev_queue_xmit+0x172/0x1770
> [ 158.795195] ? preempt_count_sub+0xf/0xd0
> [ 158.799313] __dev_queue_xmit+0x410/0x1770
> [ 158.803512] ? ___slab_alloc+0x605/0x930
> [ 158.807525] ? ___slab_alloc+0x605/0x930
> [ 158.811540] ? memcpy+0x34/0x50
> [ 158.814768] ? netdev_pick_tx+0x1c0/0x1c0
> [ 158.818895] ? __skb_clone+0x2fd/0x3d0
> [ 158.822712] ? __copy_skb_header+0x270/0x270
> [ 158.827079] ? rcu_read_lock_sched_held+0x93/0xa0
> [ 158.831903] ? kmem_cache_alloc+0x344/0x4d0
> [ 158.836199] ? skb_clone+0x123/0x230
> [ 158.839869] ? skb_split+0x820/0x820
> [ 158.843521] ? tcf_mirred+0x554/0x930 [act_mirred]
> [ 158.848407] tcf_mirred+0x554/0x930 [act_mirred]
> [ 158.853104] ? tcf_mirred_act_wants_ingress.part.2+0x10/0x10 [act_mirred]
> [ 158.860005] ? __lock_acquire+0x706/0x26e0
> [ 158.864162] ? mark_lock+0x13d/0xb40
> [ 158.867832] tcf_action_exec+0xcf/0x2a0
> [ 158.871736] tcf_classify+0xfa/0x340
> [ 158.875402] __netif_receive_skb_core+0x8e1/0x1c60
> [ 158.880334] ? nf_ingress+0x500/0x500
> [ 158.884059] ? process_backlog+0x347/0x4b0
> [ 158.888241] ? lock_acquire+0xd8/0x320
> [ 158.892050] ? process_backlog+0x1b6/0x4b0
> [ 158.896228] ? process_backlog+0xc2/0x4b0
> [ 158.900291] process_backlog+0xc2/0x4b0
> [ 158.904210] net_rx_action+0x5cc/0x980
> [ 158.908047] ? napi_complete_done+0x2c0/0x2c0
> [ 158.912525] ? rcu_read_unlock+0x80/0x80
> [ 158.916534] ? __lock_is_held+0x34/0x160
> [ 158.920541] __do_softirq+0x1d4/0x9d2
> [ 158.924308] ? trace_event_raw_event_irq_handler_exit+0x140/0x140
> [ 158.930515] run_ksoftirqd+0x1d/0x40
> [ 158.934152] smpboot_thread_fn+0x32b/0x690
> [ 158.938299] ? sort_range+0x20/0x20
> [ 158.941842] ? preempt_count_sub+0xf/0xd0
> [ 158.945940] ? schedule+0x5b/0x140
> [ 158.949412] kthread+0x206/0x300
> [ 158.952689] ? sort_range+0x20/0x20
> [ 158.956249] ? kthread_stop+0x570/0x570
> [ 158.960164] ret_from_fork+0x3a/0x50
> [ 158.963823] Code: 14 3e ff 8b 4b 78 55 4d 89 f9 41 56 41 55 48 c7 c7 a0 cf db 82 41 54 44 8b 44 24 2c 48 8b 54 24 30 48 8b 74 24 20 e8 16 94 13 ff <0f> 0b 48 c7 c7 60 8e 1f 85 48 83 c4 20 e8 55 ef a6 ff 89 74 24
> [ 158.983235] RIP: skb_panic+0xc3/0x100 RSP: ffff8801d3f27110
> [ 158.988935] ---[ end trace 5af56ee845aa6cc8 ]---
> [ 158.993641] Kernel panic - not syncing: Fatal exception in interrupt
> [ 159.000176] Kernel Offset: disabled
> [ 159.003767] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>
> Reproducer:
>
> ip link add h1 type veth peer name swp1
> ip link add h3 type veth peer name swp3
>
> ip link set dev h1 up
> ip address add 192.0.2.1/28 dev h1
>
> ip link add dev vh3 type vrf table 20
> ip link set dev h3 master vh3
> ip link set dev vh3 up
> ip link set dev h3 up
>
> ip link set dev swp3 up
> ip address add dev swp3 2001:db8:2::1/64
>
> ip link set dev swp1 up
> tc qdisc add dev swp1 clsact
>
> ip link add name gt6 type ip6gretap \
> local 2001:db8:2::1 remote 2001:db8:2::2
> ip link set dev gt6 up
>
> sleep 1
>
> tc filter add dev swp1 ingress pref 1000 matchall skip_hw \
> action mirred egress mirror dev gt6
> ping -I h1 192.0.2.2
>
> Signed-off-by: Petr Machata <petrm@...lanox.com>
> ---
Thanks for the fix.
Acked-by: William Tu <u9012063@...il.com>
> net/ipv6/ip6_gre.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
> index 69727bc..5d93c7c 100644
> --- a/net/ipv6/ip6_gre.c
> +++ b/net/ipv6/ip6_gre.c
> @@ -698,6 +698,9 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
> else
> fl6->daddr = tunnel->parms.raddr;
>
> + if (skb_cow_head(skb, dev->needed_headroom ?: tunnel->hlen))
> + return -ENOMEM;
> +
> /* Push GRE header. */
> protocol = (dev->type == ARPHRD_ETHER) ? htons(ETH_P_TEB) : proto;
>
> --
> 2.4.11
>
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