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Date: Tue, 21 Dec 2021 12:18:50 +0000
From: Ignat Korchagin <ignat@...udflare.com>
To: netdev@...r.kernel.org, edumazet@...gle.com,
"David S. Miller" <davem@...emloft.net>, dsahern@...nel.org,
kuba@...nel.org
Cc: kernel-team <kernel-team@...udflare.com>
Subject: tcp: kernel BUG at net/core/skbuff.c:3574!
Hi netdev,
While trying to reproduce a different rare bug we're seeing in
production I've triggered below on 5.15.9 kernel and confirmed on the
latest netdev master tree:
[ 53.970529][ C1] kernel BUG at net/core/skbuff.c:3574!
[ 53.981755][ C1] invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
[ 53.982634][ C1] CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted
5.16.0-rc5+ #25
[ 53.982634][ C1] Hardware name: QEMU Standard PC (Q35 + ICH9,
2009), BIOS 0.0.0 02/06/2015
[ 53.982634][ C1] RIP: 0010:skb_shift+0x13ef/0x23b0
[ 53.982634][ C1] Code: ea 03 0f b6 04 02 48 89 fa 83 e2 07 38 d0
7f 08 84 c0 0f 85 41 0c 00 00 41 80 7f 02 00 4d 8d b5 d0 00 00 00 0f
85 74 f5 ff ff <0f> 0b 4d 8d 77 20 be 04 00 00 00 4c 89 44 24 78 4c 89
f7 4c 89 8c
[ 53.982634][ C1] RSP: 0018:ffff8881008f7008 EFLAGS: 00010246
[ 53.982634][ C1] RAX: 0000000000000000 RBX: ffff8881180b4c80
RCX: 0000000000000000
[ 53.982634][ C1] RDX: 0000000000000002 RSI: ffff8881180b4d3c
RDI: ffff88810bc9cac2
[ 53.982634][ C1] RBP: ffff8881008f70b8 R08: ffff8881180b4cf4
R09: ffff8881180b4cf0
[ 53.982634][ C1] R10: ffffed1022999e5c R11: 0000000000000002
R12: 0000000000000590
[ 53.982634][ C1] R13: ffff88810f940c80 R14: ffff88810f940d50
R15: ffff88810bc9cac0
[ 53.982634][ C1] FS: 0000000000000000(0000)
GS:ffff888235880000(0000) knlGS:0000000000000000
[ 53.982634][ C1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 53.982634][ C1] CR2: 00007ff5f9b86680 CR3: 0000000108ce8004
CR4: 0000000000170ee0
[ 53.982634][ C1] Call Trace:
[ 53.982634][ C1] <TASK>
[ 53.982634][ C1] tcp_sacktag_walk+0xaba/0x18e0
[ 53.982634][ C1] ? kasan_set_free_info+0x20/0x30
[ 53.982634][ C1] ? __kasan_slab_free+0x10b/0x140
[ 53.982634][ C1] ? slab_free_freelist_hook+0xb9/0x1d0
[ 53.982634][ C1] ? kmem_cache_free+0x12f/0x350
[ 53.982634][ C1] tcp_sacktag_write_queue+0xe7b/0x3460
[ 53.982634][ C1] ? kasan_quarantine_put+0x87/0x1e0
[ 53.982634][ C1] ? tcp_sacktag_walk+0x18e0/0x18e0
[ 53.982634][ C1] ? slab_free_freelist_hook+0xb9/0x1d0
[ 53.982634][ C1] ? sk_reset_timer+0x15/0x70
[ 53.982634][ C1] ? kasan_quarantine_put+0x87/0x1e0
[ 53.982634][ C1] tcp_ack+0x2666/0x54b0
[ 53.982634][ C1] ? trace_hardirqs_on+0x1c/0x130
[ 53.982634][ C1] ? asm_sysvec_apic_timer_interrupt+0x12/0x20
[ 53.982634][ C1] ? tcp_fastretrans_alert+0x3260/0x3260
[ 53.982634][ C1] ? tcp_validate_incoming+0x128/0x1c40
[ 53.982634][ C1] ? tcp_reset+0x340/0x340
[ 53.982634][ C1] ? rcu_read_lock_sched_held+0xc/0x70
[ 53.982634][ C1] ? ktime_get+0x13c/0x160
[ 53.982634][ C1] ? trace_hardirqs_on+0x1c/0x130
[ 53.982634][ C1] ? ktime_get+0x9c/0x160
[ 53.982634][ C1] tcp_rcv_established+0x4d9/0x20f0
[ 53.982634][ C1] ? lock_release+0x700/0x700
[ 53.982634][ C1] ? tcp_data_queue+0x5160/0x5160
[ 53.982634][ C1] ? do_raw_spin_lock+0x12b/0x270
[ 53.982634][ C1] ? rwlock_bug.part.0+0x90/0x90
[ 53.982634][ C1] tcp_v4_do_rcv+0x551/0x810
[ 53.982634][ C1] tcp_v4_rcv+0x22ed/0x2ed0
[ 53.982634][ C1] ? lock_acquire+0x42a/0x4e0
[ 53.982634][ C1] ? tcp_v4_early_demux+0x8d0/0x8d0
[ 53.982634][ C1] ? lock_release+0x700/0x700
[ 53.982634][ C1] ? inet_del_offload+0x50/0x50
[ 53.982634][ C1] ? ip_local_deliver_finish+0x1e9/0x2f0
[ 53.982634][ C1] ? lock_downgrade+0x6d0/0x6d0
[ 53.982634][ C1] ip_protocol_deliver_rcu+0x96/0xaf0
[ 53.982634][ C1] ip_local_deliver_finish+0x1e0/0x2f0
[ 53.982634][ C1] ip_sublist_rcv_finish+0x211/0x440
[ 53.982634][ C1] ip_list_rcv_finish.constprop.0+0x424/0x660
[ 53.982634][ C1] ? ip_sublist_rcv_finish+0x440/0x440
[ 53.982634][ C1] ? ip_rcv_core+0x5f6/0xc10
[ 53.982634][ C1] ip_list_rcv+0x2c8/0x410
[ 53.982634][ C1] ? ip_rcv+0x480/0x480
[ 53.982634][ C1] ? ip_rcv+0x480/0x480
[ 53.982634][ C1] __netif_receive_skb_list_core+0x65c/0x910
[ 53.982634][ C1] ? process_backlog+0x710/0x710
[ 53.982634][ C1] ? rcu_read_lock_sched_held+0xc/0x70
[ 53.982634][ C1] ? rcu_read_lock_sched_held+0xc/0x70
[ 53.982634][ C1] netif_receive_skb_list_internal+0x5f9/0xcb0
[ 53.982634][ C1] ? __netif_receive_skb_list_core+0x910/0x910
[ 53.982634][ C1] ? dev_gro_receive+0x700/0x2960
[ 53.982634][ C1] ? do_raw_spin_lock+0x12b/0x270
[ 53.982634][ C1] napi_complete_done+0x188/0x6e0
[ 53.982634][ C1] gro_cell_poll+0x10c/0x1d0
[ 53.982634][ C1] ? lock_downgrade+0x6d0/0x6d0
[ 53.982634][ C1] __napi_poll+0xa1/0x530
[ 53.982634][ C1] net_rx_action+0x567/0x1270
[ 53.982634][ C1] ? napi_threaded_poll+0x470/0x470
[ 53.982634][ C1] ? try_to_wake_up+0x101/0x1500
[ 53.982634][ C1] ? migrate_swap_stop+0x7f0/0x7f0
[ 53.982634][ C1] __do_softirq+0x28a/0x9ba
[ 53.982634][ C1] ? do_softirq.part.0+0x110/0x110
[ 53.982634][ C1] ? smpboot_thread_fn+0x6b/0x8c0
[ 53.982634][ C1] run_ksoftirqd+0x32/0x60
[ 53.982634][ C1] smpboot_thread_fn+0x559/0x8c0
[ 53.982634][ C1] ? smpboot_register_percpu_thread+0x350/0x350
[ 53.982634][ C1] kthread+0x3b9/0x490
[ 53.982634][ C1] ? _raw_spin_unlock_irq+0x24/0x50
[ 53.982634][ C1] ? set_kthread_struct+0x100/0x100
[ 53.982634][ C1] ret_from_fork+0x22/0x30
[ 53.982634][ C1] </TASK>
[ 53.982634][ C1] Modules linked in:
[ 54.939907][ C1] ---[ end trace f6c264574763a26f ]---
[ 64.620726][ C1] RIP: 0010:skb_shift+0x13ef/0x23b0
[ 64.630955][ C1] Code: ea 03 0f b6 04 02 48 89 fa 83 e2 07 38 d0
7f 08 84 c0 0f 85 41 0c 00 00 41 80 7f 02 00 4d 8d b5 d0 00 00 00 0f
85 74 f5 ff ff <0f> 0b 4d 8d 77 20 be 04 00 00 00 4c 89 44 24 78 4c 89
f7 4c 89 8c
[ 64.664945][ C1] RSP: 0018:ffff8881008f7008 EFLAGS: 00010246
[ 64.675965][ C1] RAX: 0000000000000000 RBX: ffff8881180b4c80
RCX: 0000000000000000
[ 64.689670][ C1] RDX: 0000000000000002 RSI: ffff8881180b4d3c
RDI: ffff88810bc9cac2
[ 64.703383][ C1] RBP: ffff8881008f70b8 R08: ffff8881180b4cf4
R09: ffff8881180b4cf0
[ 64.717729][ C1] R10: ffffed1022999e5c R11: 0000000000000002
R12: 0000000000000590
[ 64.731377][ C1] R13: ffff88810f940c80 R14: ffff88810f940d50
R15: ffff88810bc9cac0
[ 64.744691][ C1] FS: 0000000000000000(0000)
GS:ffff888235880000(0000) knlGS:0000000000000000
[ 64.761003][ C1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 64.773726][ C1] CR2: 00007ff5f9b86680 CR3: 0000000108ce8005
CR4: 0000000000170ee0
[ 64.789673][ C1] Kernel panic - not syncing: Fatal exception in interrupt
[ 64.794751][ C1] Kernel Offset: 0x26000000 from
0xffffffff81000000 (relocation range:
0xffffffff80000000-0xffffffffbfffffff)
[ 64.794751][ C1] ---[ end Kernel panic - not syncing: Fatal
exception in interrupt ]---
We are somehow triggering the BUG_ON directive in skbuff.c. Here is a
bash script which triggers this in QEMU (may need to run it couple of
times in a row):
#!/bin/bash -xe
ip netns delete left 2>/dev/null || true
ip netns delete right 2>/dev/null || true
ip netns add left
ip netns add right
ip link add veth-left netns left type veth peer veth-right netns right
ip -n left link set lo up
ip -n left link set veth-left up
ip -n right link set lo up
ip -n right link set veth-right up
ip -n left addr add 192.168.13.5/24 dev veth-left
ip -n right addr add 192.168.13.7/24 dev veth-right
ip -n left tunnel add gre-left mode gre remote 192.168.13.7 local
192.168.13.5 ttl 255
ip -n left link set gre-left up
ip -n left addr add 10.10.10.5/24 dev gre-left
ip -n right tunnel add gre-right mode gre remote 192.168.13.5 local
192.168.13.7 ttl 255
ip -n right link set gre-right up
ip -n right addr add 10.10.10.7/24 dev gre-right
ip netns exec left ethtool -K veth-left gro on tso off
ip netns exec right ethtool -K veth-right gro on tso off
(ip netns exec right iperf3 -s -D && ip netns exec left iperf3 -c
10.10.10.7 -P 16 -b 100M) &
sleep 5
ip netns delete left
ip netns delete right
# end of script
QEMU command line:
qemu-system-x86_64 -nographic -cpu host \
-enable-kvm \
-machine q35 \
-smp 8 \
-m 8G \
-drive
if=pflash,format=raw,readonly=on,file=/usr/share/OVMF/OVMF_CODE.fd \
-drive
if=pflash,format=raw,file=/usr/share/OVMF/OVMF_VARS.fd \
-drive file=/work/rootfs.img,format=qcow2 \
-nic user,model=virtio-net-pci,hostfwd=tcp::22-:22 \
-kernel vmlinuz \
-append "console=ttyS0 root=/dev/sda rw
systemd.unified_cgroup_hierarchy=0"
Userspace: vanilla Debian Bullseye
I didn't look deeply into it myself yet, but I think I don't even have
enough knowledge about this code yet, so asking here for help.
Thanks,
Ignat
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