netdev - Re: [PATCH net] net/tunnel: wait until all sk_user_data reader finish before releasing the sock

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Date:   Thu, 8 Dec 2022 13:38:55 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        William Tu <u9012063@...il.com>, Andy Zhou <azhou@...ira.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Jianlin Shi <jishi@...hat.com>,
        Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [PATCH net] net/tunnel: wait until all sk_user_data reader
 finish before releasing the sock

Thu, Dec 08, 2022 at 01:04:52PM CET, liuhangbin@...il.com wrote:
>There is a race condition in vxlan that when deleting a vxlan device
>during receiving packets, there is a possibility that the sock is
>released after getting vxlan_sock vs from sk_user_data. Then in
>later vxlan_ecn_decapsulate(), vxlan_get_sk_family() we will got
>NULL pointer dereference. e.g.
>
>   #0 [ffffa25ec6978a38] machine_kexec at ffffffff8c669757
>   #1 [ffffa25ec6978a90] __crash_kexec at ffffffff8c7c0a4d
>   #2 [ffffa25ec6978b58] crash_kexec at ffffffff8c7c1c48
>   #3 [ffffa25ec6978b60] oops_end at ffffffff8c627f2b
>   #4 [ffffa25ec6978b80] page_fault_oops at ffffffff8c678fcb
>   #5 [ffffa25ec6978bd8] exc_page_fault at ffffffff8d109542
>   #6 [ffffa25ec6978c00] asm_exc_page_fault at ffffffff8d200b62
>      [exception RIP: vxlan_ecn_decapsulate+0x3b]
>      RIP: ffffffffc1014e7b  RSP: ffffa25ec6978cb0  RFLAGS: 00010246
>      RAX: 0000000000000008  RBX: ffff8aa000888000  RCX: 0000000000000000
>      RDX: 000000000000000e  RSI: ffff8a9fc7ab803e  RDI: ffff8a9fd1168700
>      RBP: ffff8a9fc7ab803e   R8: 0000000000700000   R9: 00000000000010ae
>      R10: ffff8a9fcb748980  R11: 0000000000000000  R12: ffff8a9fd1168700
>      R13: ffff8aa000888000  R14: 00000000002a0000  R15: 00000000000010ae
>      ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>   #7 [ffffa25ec6978ce8] vxlan_rcv at ffffffffc10189cd [vxlan]
>   #8 [ffffa25ec6978d90] udp_queue_rcv_one_skb at ffffffff8cfb6507
>   #9 [ffffa25ec6978dc0] udp_unicast_rcv_skb at ffffffff8cfb6e45
>  #10 [ffffa25ec6978dc8] __udp4_lib_rcv at ffffffff8cfb8807
>  #11 [ffffa25ec6978e20] ip_protocol_deliver_rcu at ffffffff8cf76951
>  #12 [ffffa25ec6978e48] ip_local_deliver at ffffffff8cf76bde
>  #13 [ffffa25ec6978ea0] __netif_receive_skb_one_core at ffffffff8cecde9b
>  #14 [ffffa25ec6978ec8] process_backlog at ffffffff8cece139
>  #15 [ffffa25ec6978f00] __napi_poll at ffffffff8ceced1a
>  #16 [ffffa25ec6978f28] net_rx_action at ffffffff8cecf1f3
>  #17 [ffffa25ec6978fa0] __softirqentry_text_start at ffffffff8d4000ca
>  #18 [ffffa25ec6978ff0] do_softirq at ffffffff8c6fbdc3
>
>Reproducer: https://github.com/Mellanox/ovs-tests/blob/master/test-ovs-vxlan-remove-tunnel-during-traffic.sh
>
>Fix this by waiting for all sk_user_data reader to finish before
>releasing the sock.
>
>Reported-by: Jianlin Shi <jishi@...hat.com>
>Suggested-by: Jakub Sitnicki <jakub@...udflare.com>
>Fixes: 6a93cc905274 ("udp-tunnel: Add a few more UDP tunnel APIs")
>Signed-off-by: Hangbin Liu <liuhangbin@...il.com>

Reviewed-by: Jiri Pirko <jiri@...dia.com>