Date:   Tue, 11 Oct 2022 10:57:05 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     seh@...ix.com, Herbert Xu <herbert@...dor.apana.org.au>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: kernel BUG at net/core/skbuff.c:4219


On 10/11/22 09:56, Jeremi Piotrowski wrote:
> Hi,
>
> One of our Flatcar users has been hitting the kernel BUG in the subject line
> for the past year (https://github.com/flatcar/Flatcar/issues/378). This was
> first reported when on 5.10.25, but has been happening across kernel updates,
> most recently with 5.15.63. The nodes where this happens are AWS EC2 instances,
> using ENA and calico networking in eBPF mode with VXLAN encapsulation. When
> GRO/GSO is enabled, the host hits this bug and prints the following stacktrace:


I suspect eBPF code lowers gso_size ?

gso stack is not able to arbitrarily segment a GRO packet after gso_size 
being changed.


>
> [Mon Oct 10 18:22:24 2022] ------------[ cut here ]------------
> [Mon Oct 10 18:22:24 2022] kernel BUG at net/core/skbuff.c:4219!
> [Mon Oct 10 18:22:24 2022] invalid opcode: 0000 [#1] SMP PTI
> [Mon Oct 10 18:22:24 2022] CPU: 6 PID: 0 Comm: swapper/6 Not tainted 5.15.63-flatcar #1
> [Mon Oct 10 18:22:24 2022] Hardware name: Amazon EC2 z1d.12xlarge/, BIOS 1.0 10/16/2017
> [Mon Oct 10 18:22:24 2022] RIP: 0010:skb_segment+0xc70/0xe80
> [Mon Oct 10 18:22:24 2022] Code: 44 24 50 48 89 44 24 30 48 8b 44 24 10 48 89 44 24 50 e9 16 f7 ff ff 0f 0b 89 44 24 2c c7 44 24 4c 00 00 00 00 e9 44 fe ff ff <0f> 0b 0f 0b 0f 0b 41 8b 7d 74 85 ff 0f 85 91 01 00 00 49 8b 95 c0
> [Mon Oct 10 18:22:24 2022] RSP: 0018:ffffa2d38c780838 EFLAGS: 00010246
> [Mon Oct 10 18:22:24 2022] RAX: ffff8954dd8312c0 RBX: ffff89293fbde300 RCX: ffff8957bd3d2fa0
> [Mon Oct 10 18:22:24 2022] RDX: 0000000000000000 RSI: ffff89293fbde2c0 RDI: ffffffffffffffff
> [Mon Oct 10 18:22:24 2022] RBP: ffffa2d38c780908 R08: 0000000000009db6 R09: 0000000000000000
> [Mon Oct 10 18:22:24 2022] R10: 000000000000a356 R11: 000000000000a31a R12: 000000000000000b
> [Mon Oct 10 18:22:24 2022] R13: ffff892940566100 R14: 000000000000a31a R15: ffff891ad0e5c600
> [Mon Oct 10 18:22:24 2022] FS:  0000000000000000(0000) GS:ffff8948b9b80000(0000) knlGS:0000000000000000
> [Mon Oct 10 18:22:24 2022] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [Mon Oct 10 18:22:24 2022] CR2: 000000c011faf000 CR3: 0000000d66a0a001 CR4: 00000000007706e0
> [Mon Oct 10 18:22:24 2022] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [Mon Oct 10 18:22:24 2022] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [Mon Oct 10 18:22:24 2022] PKRU: 55555554
> [Mon Oct 10 18:22:24 2022] Call Trace:
> [Mon Oct 10 18:22:24 2022]  <IRQ>
> [Mon Oct 10 18:22:24 2022] ? csum_block_add_ext (include/net/checksum.h:117)
> [Mon Oct 10 18:22:24 2022] ? reqsk_fastopen_remove (include/linux/bitops.h:119 include/net/checksum.h:87 include/net/checksum.h:94 include/net/checksum.h:100)
> [Mon Oct 10 18:22:24 2022] tcp_gso_segment (net/ipv4/tcp_offload.c:99)
> [Mon Oct 10 18:22:24 2022] inet_gso_segment (net/ipv4/af_inet.c:1385)
> [Mon Oct 10 18:22:24 2022] skb_mac_gso_segment (net/core/dev.c:3339)
> [Mon Oct 10 18:22:24 2022] __skb_gso_segment (net/core/dev.c:3414 (discriminator 3))
> [Mon Oct 10 18:22:24 2022] ? netif_skb_features (include/net/mpls.h:21 net/core/dev.c:3463 net/core/dev.c:3483 net/core/dev.c:3574)
> [Mon Oct 10 18:22:24 2022] validate_xmit_skb.constprop.0 (net/core/dev.c:3672)
> [Mon Oct 10 18:22:24 2022] validate_xmit_skb_list (net/core/dev.c:3722)
> [Mon Oct 10 18:22:24 2022] sch_direct_xmit (net/sched/sch_generic.c:327)
> [Mon Oct 10 18:22:24 2022] __dev_queue_xmit (net/core/dev.c:3858 net/core/dev.c:4185)
> [Mon Oct 10 18:22:24 2022] ip_finish_output2 (include/net/neighbour.h:500 include/net/neighbour.h:514 net/ipv4/ip_output.c:228)
> [Mon Oct 10 18:22:24 2022] ? ip_route_input_rcu (net/ipv4/route.c:1745 net/ipv4/route.c:2499 net/ipv4/route.c:2458)
> [Mon Oct 10 18:22:24 2022] ? skb_gso_validate_network_len (net/core/skbuff.c:5561 net/core/skbuff.c:5636)
> [Mon Oct 10 18:22:24 2022] ? __ip_finish_output (net/ipv4/ip_output.c:249 net/ipv4/ip_output.c:301 net/ipv4/ip_output.c:288)
> [Mon Oct 10 18:22:24 2022] ip_sublist_rcv_finish (include/net/dst.h:460 net/ipv4/ip_input.c:565)
> [Mon Oct 10 18:22:24 2022] ip_sublist_rcv (net/ipv4/ip_input.c:624)
> [Mon Oct 10 18:22:24 2022] ? ip_sublist_rcv (net/ipv4/ip_input.c:422)
> [Mon Oct 10 18:22:24 2022] ip_list_rcv (net/ipv4/ip_input.c:659)
> [Mon Oct 10 18:22:24 2022] __netif_receive_skb_list_core (net/core/dev.c:5498 net/core/dev.c:5546)
> [Mon Oct 10 18:22:24 2022] netif_receive_skb_list_internal (net/core/dev.c:5600 net/core/dev.c:5689)
> [Mon Oct 10 18:22:24 2022] ? inet_gro_complete (net/ipv4/af_inet.c:1645)
> [Mon Oct 10 18:22:24 2022] napi_gro_complete.constprop.0.isra.0 (include/linux/list.h:35 net/core/dev.c:5844 net/core/dev.c:5839 net/core/dev.c:5856 net/core/dev.c:5892)
> [Mon Oct 10 18:22:24 2022] dev_gro_receive (net/core/dev.c:6119)
> [Mon Oct 10 18:22:24 2022] napi_gro_receive (net/core/dev.c:6223)
> [Mon Oct 10 18:22:24 2022]  0xffffffffc069d699
> [Mon Oct 10 18:22:24 2022] ? scheduler_tick (kernel/sched/core.c:7053 kernel/sched/core.c:5278)
> [Mon Oct 10 18:22:24 2022] __napi_poll (net/core/dev.c:7005)
> [Mon Oct 10 18:22:24 2022] net_rx_action (net/core/dev.c:7074 net/core/dev.c:7159)
> [Mon Oct 10 18:22:24 2022] __do_softirq (arch/x86/include/asm/jump_label.h:27 include/linux/jump_label.h:212 include/trace/events/irq.h:142 kernel/softirq.c:559)
> [Mon Oct 10 18:22:24 2022] irq_exit_rcu (kernel/softirq.c:432 kernel/softirq.c:636 kernel/softirq.c:648)
> [Mon Oct 10 18:22:24 2022] common_interrupt (arch/x86/kernel/irq.c:240 (discriminator 14))
> [Mon Oct 10 18:22:24 2022]  </IRQ>
> [Mon Oct 10 18:22:24 2022]  <TASK>
> [Mon Oct 10 18:22:24 2022]  asm_common_interrupt+0x21/0x40
> [Mon Oct 10 18:22:24 2022] RIP: 0010:cpuidle_enter_state+0xc7/0x350
> [Mon Oct 10 18:22:24 2022] Code: 8b 3d f5 e1 9b 4d e8 08 bb a7 ff 49 89 c5 0f 1f 44 00 00 31 ff e8 09 c9 a7 ff 45 84 ff 0f 85 fe 00 00 00 fb 66 0f 1f 44 00 00 <45> 85 f6 0f 88 0a 01 00 00 49 63 c6 4c 2b 2c 24 48 8d 14 40 48 8d
> [Mon Oct 10 18:22:24 2022] RSP: 0018:ffffa2d38c527ea8 EFLAGS: 00000246
> [Mon Oct 10 18:22:24 2022] RAX: ffff8948b9bac100 RBX: 0000000000000003 RCX: 00000000ffffffff
> [Mon Oct 10 18:22:24 2022] RDX: 0000000000000006 RSI: 0000000000000006 RDI: 0000000000000000
> [Mon Oct 10 18:22:24 2022] RBP: ffff8948b9bb6000 R08: 0000043f38b90644 R09: 0000043f6c0b1df3
> [Mon Oct 10 18:22:24 2022] R10: 0000000000000014 R11: 0000000000000008 R12: ffffffffb3bbd7e0
> [Mon Oct 10 18:22:24 2022] R13: 0000043f38b90644 R14: 0000000000000003 R15: 0000000000000000
> [Mon Oct 10 18:22:24 2022]  ? cpuidle_enter_state+0xb7/0x350
> [Mon Oct 10 18:22:24 2022]  cpuidle_enter+0x29/0x40
> [Mon Oct 10 18:22:24 2022]  do_idle+0x1e9/0x280
> [Mon Oct 10 18:22:24 2022]  cpu_startup_entry+0x19/0x20
> [Mon Oct 10 18:22:24 2022]  secondary_startup_64_no_verify+0xc2/0xcb
> [Mon Oct 10 18:22:24 2022]  </TASK>
> [Mon Oct 10 18:22:24 2022] Modules linked in: xt_CT ip_set_hash_net ip_set vxlan cls_bpf sch_ingress veth xt_comment xt_mark xt_conntrack nft_chain_nat xt_MASQUERADE nf_nat nf_conntrack_netlink nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 xfrm_user xfrm_algo nft_counter xt_addrtype nft_compat nf_tables nfnetlink nls_ascii nls_cp437 vfat fat mousedev intel_rapl_msr intel_rapl_common psmouse evdev i2c_piix4 i2c_core button sch_fq_codel fuse configfs ext4 crc16 mbcache jbd2 dm_verity dm_bufio aesni_intel nvme nvme_core libaes crypto_simd ena cryptd t10_pi crc_t10dif crct10dif_generic crct10dif_common btrfs blake2b_generic zstd_compress lzo_compress raid6_pq libcrc32c crc32c_generic crc32c_intel dm_mirror dm_region_hash dm_log dm_mod qla4xxx iscsi_boot_sysfs iscsi_tcp libiscsi_tcp libiscsi br_netfilter bridge scsi_transport_iscsi stp llc overlay scsi_mod scsi_common
> [Mon Oct 10 18:22:24 2022] ---[ end trace 86a2732b8f4d0b13 ]---
>
> Disabling GSO/GRO *seems* to prevent the BUG_ON() from getting hit but is too
> costly in terms of performance. There are also suggestions that this happens
> more often under heavy network load, and has also been observed when running on
> Vmware.
>
> If anyone has any suggestions or needs more information to come up with a
> theory, we'd love to get to the bottom of this.
>
> Jeremi

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