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Hello,
On Tue, 7 May 2019, hujunwei wrote:
> From: Junwei Hu <hujunwei4@xxxxxxxxxx>
>
> When Tcp send RST packet in ipvs, crash occurs with the following
> stack trace:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> PID: 0 COMMAND: "swapper/2"
> TASK: ffff9ec83889bf40 (1 of 4) [THREAD_INFO: ffff9ec8388b0000]
> CPU: 2 STATE: TASK_RUNNING (PANIC)
> [exception RIP: __ip_vs_get_out_rt_v6+1250]
> RIP: ffffffffc0d566f2 RSP: ffff9ec83ed03c68 RFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff9ec835e85000 RCX: 000000000005e1f9
> RDX: 000000000005e1f8 RSI: 0000000000000200 RDI: ffff9ec83e801b00
> RBP: ffff9ec83ed03cd8 R8: 000000000001bb40 R9: ffffffffc0d5673f
> R10: ffff9ec83ed1bb40 R11: ffffe2d384d4fdc0 R12: ffff9ec7b7ad5900
> R13: 0000000000000000 R14: 0000000000000007 R15: ffff9ec8353f7580
> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
> [ffff9ec83ed03ce0] ip_vs_fnat_xmit_v6 at ffffffffc0d5b42c [ip_vs]
> [ffff9ec83ed03d70] tcp_send_rst_ipv6 at ffffffffc0d6542a [ip_vs]
> [ffff9ec83ed03df8] tcp_conn_expire_handler at ffffffffc0d65823 [ip_vs]
> [ffff9ec83ed03e20] ip_vs_conn_expire at ffffffffc0d42373 [ip_vs]
> [ffff9ec83ed03e70] call_timer_fn at ffffffffae0a6b58
> [ffff9ec83ed03ea8] run_timer_softirq at ffffffffae0a904d
> [ffff9ec83ed03f20] __do_softirq at ffffffffae09fa85
> [ffff9ec83ed03f90] call_softirq at ffffffffae739dac
> [ffff9ec83ed03fa8] do_softirq at ffffffffae02e62b
> [ffff9ec83ed03fc0] irq_exit at ffffffffae09fe25
> [ffff9ec83ed03fd8] smp_apic_timer_interrupt at ffffffffae73b158
> [ffff9ec83ed03ff0] apic_timer_interrupt at ffffffffae737872
>
> TCP connection timeout and send a RST packet, the skb is alloc
> by alloc_skb, the pointer skb->dev and skb_dst(skb) is NULL,
> however, ipv6 route unreach at that time, so go into err_unreach.
> In err_unreach, crash occurs when skb->dev and skb_dst(skb) is NULL.
I guess, this is a modified IPVS module and the problem
can not occur in mainline kernel. ip_vs_in() and ip_vs_out() already
have check for skb_dst(). May be you generate skb without attached
route, so skb_dst is NULL. Also, note that decrement_ttl() has similar
code.
> The code is added by the following patch:
> commit 326bf17ea5d4 ("ipvs: fix ipv6 route unreach panic")
> because the ip6_link_failure function requires the skb->dev
> in icmp6_send with that version.
>
> This patch only fix the problem in specific scene, and icmp6_send in
> current version is robust against null skb->dev by adding the
> following patch.
> commit 8d9336704521
> ("ipv6: make icmp6_send() robust against null skb->dev")
>
> So I delete the code, make __ip_vs_get_out_rt_v6() robust, when
> skb->dev and skb_dst(skb) is NULL.
>
> Fixes: 326bf17ea5d4 ("ipvs: fix ipv6 route unreach panic")
> Signed-off-by: Junwei Hu <hujunwei4@xxxxxxxxxx>
> Reported-by: Wenhao Zhang <zhangwenhao8@xxxxxxxxxx>
> ---
> net/netfilter/ipvs/ip_vs_xmit.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
> index 175349fcf91f..e2bb6c223396 100644
> --- a/net/netfilter/ipvs/ip_vs_xmit.c
> +++ b/net/netfilter/ipvs/ip_vs_xmit.c
> @@ -561,13 +561,6 @@ __ip_vs_get_out_rt_v6(struct netns_ipvs *ipvs, int
> skb_af, struct sk_buff *skb,
> return -1;
>
> err_unreach:
> - /* The ip6_link_failure function requires the dev field to be set
> - * in order to get the net (further for the sake of fwmark
> - * reflection).
> - */
> - if (!skb->dev)
> - skb->dev = skb_dst(skb)->dev;
> -
> dst_link_failure(skb);
> return -1;
> }
> --
> 2.21.GIT
Regards
--
Julian Anastasov <ja@xxxxxx>
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