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Subject: Re: 5.3-rc3-ish VM crash: RIP: 0010:tcp_trim_head+0x20/0xe0
To:     Eric Dumazet <eric.dumazet@gmail.com>,
        netdev <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <27aebb57-0ca9-fba3-092f-39131ad2b648@eikelenboom.it>
 <4d803565-b716-42ab-1db8-3dcade91e939@gmail.com>
 <674de4ab-c37f-7787-f95a-3ae0f52bc196@eikelenboom.it>
 <59dd3497-6d08-1e0e-7a4f-b121b850a24f@gmail.com>
From:   Sander Eikelenboom <linux@eikelenboom.it>
Message-ID: <4f953b39-7600-cdc3-1f30-203dbdfd7fa7@eikelenboom.it>
Date:   Sat, 24 Aug 2019 12:22:24 +0200
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On 17/08/2019 18:35, Eric Dumazet wrote:
> 
> 
> On 8/17/19 10:24 AM, Sander Eikelenboom wrote:
>> On 12/08/2019 19:56, Eric Dumazet wrote:
>>>
>>>
>>> On 8/12/19 2:50 PM, Sander Eikelenboom wrote:
>>>> L.S.,
>>>>
>>>> While testing a somewhere-after-5.3-rc3 kernel (which included the latest net merge (33920f1ec5bf47c5c0a1d2113989bdd9dfb3fae9),
>>>> one of my Xen VM's (which gets quite some network load) crashed.
>>>> See below for the stacktrace.
>>>>
>>>> Unfortunately I haven't got a clear trigger, so bisection doesn't seem to be an option at the moment. 
>>>> I haven't encountered this on 5.2, so it seems to be an regression against 5.2.
>>>>
>>>> Any ideas ?
>>>>
>>>> --
>>>> Sander
>>>>
>>>>
>>>> [16930.653595] general protection fault: 0000 [#1] SMP NOPTI
>>>> [16930.653624] CPU: 0 PID: 3275 Comm: rsync Not tainted 5.3.0-rc3-20190809-doflr+ #1
>>>> [16930.653657] RIP: 0010:tcp_trim_head+0x20/0xe0
>>>> [16930.653677] Code: 2e 0f 1f 84 00 00 00 00 00 90 41 54 41 89 d4 55 48 89 fd 53 48 89 f3 f6 46 7e 01 74 2f 8b 86 bc 00 00 00 48 03 86 c0 00 00 00 <8b> 40 20 66 83 f8 01 74 19 31 d2 31 f6 b9 20 0a 00 00 48 89 df e8
>>>> [16930.653741] RSP: 0000:ffffc90000003ad8 EFLAGS: 00010286
>>>> [16930.653762] RAX: fffe888005bf62c0 RBX: ffff8880115fb800 RCX: 000000008010000b
>>>
>>> crash in " mov    0x20(%rax),%eax"   and RAX=fffe888005bf62c0 (not a valid kernel address)
>>>
>>> Look like one bit corruption maybe.
>>>
>>> Nothing comes to mind really between 5.2 and 53 that could explain this.
>>>
>>>> [16930.653791] RDX: 00000000000005a0 RSI: ffff8880115fb800 RDI: ffff888016b00880
>>>> [16930.653819] RBP: ffff888016b00880 R08: 0000000000000001 R09: 0000000000000000
>>>> [16930.653848] R10: ffff88800ae00800 R11: 00000000bfe632e6 R12: 00000000000005a0
>>>> [16930.653875] R13: 0000000000000001 R14: 00000000bfe62d46 R15: 0000000000000004
>>>> [16930.653913] FS:  00007fe71fe2cb80(0000) GS:ffff88801f200000(0000) knlGS:0000000000000000
>>>> [16930.653943] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [16930.653965] CR2: 000055de0f3e7000 CR3: 0000000011f32000 CR4: 00000000000006f0
>>>> [16930.653993] Call Trace:
>>>> [16930.654005]  <IRQ>
>>>> [16930.654018]  tcp_ack+0xbb0/0x1230
>>>> [16930.654033]  tcp_rcv_established+0x2e8/0x630
>>>> [16930.654053]  tcp_v4_do_rcv+0x129/0x1d0
>>>> [16930.654070]  tcp_v4_rcv+0xac9/0xcb0
>>>> [16930.654088]  ip_protocol_deliver_rcu+0x27/0x1b0
>>>> [16930.654109]  ip_local_deliver_finish+0x3f/0x50
>>>> [16930.654128]  ip_local_deliver+0x4d/0xe0
>>>> [16930.654145]  ? ip_protocol_deliver_rcu+0x1b0/0x1b0
>>>> [16930.654163]  ip_rcv+0x4c/0xd0
>>>> [16930.654179]  __netif_receive_skb_one_core+0x79/0x90
>>>> [16930.654200]  netif_receive_skb_internal+0x2a/0xa0
>>>> [16930.654219]  napi_gro_receive+0xe7/0x140
>>>> [16930.654237]  xennet_poll+0x9be/0xae0
>>>> [16930.654254]  net_rx_action+0x136/0x340
>>>> [16930.654271]  __do_softirq+0xdd/0x2cf
>>>> [16930.654287]  irq_exit+0x7a/0xa0
>>>> [16930.654304]  xen_evtchn_do_upcall+0x27/0x40
>>>> [16930.654320]  xen_hvm_callback_vector+0xf/0x20
>>>> [16930.654339]  </IRQ>
>>>> [16930.654349] RIP: 0033:0x55de0d87db99
>>>> [16930.654364] Code: 00 00 48 89 7c 24 f8 45 39 fe 45 0f 42 fe 44 89 7c 24 f4 eb 09 0f 1f 40 00 83 e9 01 74 3e 89 f2 48 63 f8 4c 01 d2 44 38 1c 3a <75> 25 44 38 6c 3a ff 75 1e 41 0f b6 3c 24 40 38 3a 75 14 41 0f b6
>>>> [16930.654432] RSP: 002b:00007ffd5531eec8 EFLAGS: 00000a87 ORIG_RAX: ffffffffffffff0c
>>>> [16930.655004] RAX: 0000000000000002 RBX: 000055de0f3e8e50 RCX: 000000000000007f
>>>> [16930.655034] RDX: 000055de0f3dc2d2 RSI: 0000000000003492 RDI: 0000000000000002
>>>> [16930.655062] RBP: 0000000000007fff R08: 00000000000080ea R09: 00000000000001f0
>>>> [16930.655089] R10: 000055de0f3d8e40 R11: 0000000000000094 R12: 000055de0f3e0f2a
>>>> [16930.655116] R13: 0000000000000010 R14: 0000000000007f16 R15: 0000000000000080
>>>> [16930.655144] Modules linked in:
>>>> [16930.655200] ---[ end trace 533367c95501b645 ]---
>>>> [16930.655223] RIP: 0010:tcp_trim_head+0x20/0xe0
>>>> [16930.655243] Code: 2e 0f 1f 84 00 00 00 00 00 90 41 54 41 89 d4 55 48 89 fd 53 48 89 f3 f6 46 7e 01 74 2f 8b 86 bc 00 00 00 48 03 86 c0 00 00 00 <8b> 40 20 66 83 f8 01 74 19 31 d2 31 f6 b9 20 0a 00 00 48 89 df e8
>>>> [16930.655312] RSP: 0000:ffffc90000003ad8 EFLAGS: 00010286
>>>> [16930.655331] RAX: fffe888005bf62c0 RBX: ffff8880115fb800 RCX: 000000008010000b
>>>> [16930.655360] RDX: 00000000000005a0 RSI: ffff8880115fb800 RDI: ffff888016b00880
>>>> [16930.655387] RBP: ffff888016b00880 R08: 0000000000000001 R09: 0000000000000000
>>>> [16930.655414] R10: ffff88800ae00800 R11: 00000000bfe632e6 R12: 00000000000005a0
>>>> [16930.655441] R13: 0000000000000001 R14: 00000000bfe62d46 R15: 0000000000000004
>>>> [16930.655475] FS:  00007fe71fe2cb80(0000) GS:ffff88801f200000(0000) knlGS:0000000000000000
>>>> [16930.655502] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [16930.655525] CR2: 000055de0f3e7000 CR3: 0000000011f32000 CR4: 00000000000006f0
>>>> [16930.655553] Kernel panic - not syncing: Fatal exception in interrupt
>>>> [16930.655789] Kernel Offset: disabled
>>>>
>>
>> Hi Eric,
>>
>> Got another VM crash, with a slightly different stacktrace this time around.
>> Still networking though.
>>
>> --
>> Sander
>>
>> [112522.697498] general protection fault: 0000 [#1] SMP NOPTI
>> [112522.697555] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.3.0-rc4-20190812-doflr+ #1
>> [112522.697592] RIP: 0010:skb_shift+0x63/0x430
>> [112522.697608] Code: bc 00 00 00 48 03 8f c0 00 00 00 f6 41 03 08 74 07 48 83 79 28 00 75 d0 8b 8e bc 00 00 00 48 03 8e c0 00 00 00 48 85 f6 74 0a <f6> 41 03 08 0f 85 09 03 00 00 49 89 fd 8b bf bc 00 00 00 41 89 
> 
> 
> 
> crash in "testb  $0x8,0x3(%rcx)"  with RCX==fffe8880117da6c0
> 
> Same strange looking address on x86_64
> 
> I have no idea.
> 
>> [112522.697673] RSP: 0018:ffffc900000039b0 EFLAGS: 00010286
>> [112522.697693] RAX: 00000000000005a0 RBX: ffff8880117fb800 RCX: fffe8880117da6c0
>> [112522.697721] RDX: 00000000000005a0 RSI: ffff8880117fb800 RDI: ffff88800ae58000
>> [112522.697748] RBP: ffffc900000039e8 R08: 000000000004cfe0 R09: 00000000000005a0
>> [112522.697775] R10: 00000000000005a0 R11: ffff8880117fb800 R12: 0000000000000000
>> [112522.697803] R13: 00000000c95a98c2 R14: 0000000000000000 R15: ffff88800ae58000
>> [112522.697839] FS:  0000000000000000(0000) GS:ffff88801f200000(0000) knlGS:0000000000000000
>> [112522.697869] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [112522.697895] CR2: 00007f9210d8e078 CR3: 000000000b660000 CR4: 00000000000006f0
>> [112522.697925] Call Trace:
>> [112522.697938]  <IRQ>
>> [112522.697951]  tcp_sacktag_walk+0x2af/0x480
>> [112522.697967]  tcp_sacktag_write_queue+0x34d/0x820
>> [112522.697986]  ? ip_forward_options.cold.0+0x1c/0x1c
>> [112522.698007]  tcp_ack+0xb8c/0x1230
>> [112522.698023]  ? tcp_event_new_data_sent+0x4a/0x90
>> [112522.698043]  tcp_rcv_established+0x14c/0x630
>> [112522.698064]  tcp_v4_do_rcv+0x129/0x1d0
>> [112522.698081]  tcp_v4_rcv+0xac9/0xcb0
>> [112522.698099]  ip_protocol_deliver_rcu+0x27/0x1b0
>> [112522.698119]  ip_local_deliver_finish+0x3f/0x50
>> [112522.698139]  ip_local_deliver+0x4d/0xe0
>> [112522.698155]  ? ip_protocol_deliver_rcu+0x1b0/0x1b0
>> [112522.698177]  ip_rcv+0x4c/0xd0
>> [112522.698194]  __netif_receive_skb_one_core+0x79/0x90
>> [112522.698215]  netif_receive_skb_internal+0x2a/0xa0
>> [112522.698237]  napi_gro_receive+0xe7/0x140
>> [112522.698255]  xennet_poll+0x9be/0xae0
>> [112522.698271]  net_rx_action+0x136/0x340
>> [112522.698288]  __do_softirq+0xdd/0x2cf
>> [112522.698304]  irq_exit+0x7a/0xa0
>> [112522.698321]  xen_evtchn_do_upcall+0x27/0x40
>> [112522.698340]  xen_hvm_callback_vector+0xf/0x20
>> [112522.698359]  </IRQ>
>> [112522.698373] RIP: 0010:native_safe_halt+0xe/0x10
>> [112522.698392] Code: 48 8b 04 25 c0 6b 01 00 f0 80 48 02 20 48 8b 00 a8 08 75 c4 eb 80 90 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 54 fb 41 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 44 fb 41 00 f4 c3 90 90 41 55 41 54
>> [112522.699522] RSP: 0018:ffffffff82a03e90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff0c
>> [112522.699552] RAX: 0001a54800000000 RBX: 0000000000000000 RCX: 0000000000000001
>> [112522.699580] RDX: 0000000002b9f9b6 RSI: 0000000000000087 RDI: 0000000000000000
>> [112522.699608] RBP: 0000000000000000 R08: 000000001eb5c3cb R09: ffffffff82a08460
>> [112522.699634] R10: 000000000002e46e R11: 0000000000000000 R12: 0000000000000000
>> [112522.699662] R13: 0000000000000000 R14: ffffffff8326e0a0 R15: 0000000000000000
>> [112522.699692]  default_idle+0x17/0x140
>> [112522.699709]  do_idle+0x1ee/0x210
>> [112522.699726]  cpu_startup_entry+0x14/0x20
>> [112522.699743]  start_kernel+0x4e9/0x50b
>> [112522.699760]  secondary_startup_64+0xa4/0xb0
>> [112522.699780] Modules linked in:
>> [112522.699829] ---[ end trace 3b8db3603485e952 ]---
>> [112522.699850] RIP: 0010:skb_shift+0x63/0x430
>> [112522.699866] Code: bc 00 00 00 48 03 8f c0 00 00 00 f6 41 03 08 74 07 48 83 79 28 00 75 d0 8b 8e bc 00 00 00 48 03 8e c0 00 00 00 48 85 f6 74 0a <f6> 41 03 08 0f 85 09 03 00 00 49 89 fd 8b bf bc 00 00 00 41 89 d4
>> [112522.699938] RSP: 0018:ffffc900000039b0 EFLAGS: 00010286
>> [112522.699959] RAX: 00000000000005a0 RBX: ffff8880117fb800 RCX: fffe8880117da6c0
>> [112522.699986] RDX: 00000000000005a0 RSI: ffff8880117fb800 RDI: ffff88800ae58000
>> [112522.700013] RBP: ffffc900000039e8 R08: 000000000004cfe0 R09: 00000000000005a0
>> [112522.700041] R10: 00000000000005a0 R11: ffff8880117fb800 R12: 0000000000000000
>> [112522.700067] R13: 00000000c95a98c2 R14: 0000000000000000 R15: ffff88800ae58000
>> [112522.700111] FS:  0000000000000000(0000) GS:ffff88801f200000(0000) knlGS:0000000000000000
>> [112522.700140] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [112522.700165] CR2: 00007f9210d8e078 CR3: 000000000b660000 CR4: 00000000000006f0
>> [112522.700201] Kernel panic - not syncing: Fatal exception in interrupt
>> [112522.702992] Kernel Offset: disabled
>>
>>

And another one (on an RC5 kernel now), but I probably know the answer :( ...
Is there any extra debugging options I can turn on that could shed some more light on this ?
(it doesn't seem to be an incident and happens at about 3 to 4 days of uptime, so bisecting is not a realistic option).

--
Sander


[327011.399239] general protection fault: 0000 [#1] SMP NOPTI
[327011.399271] CPU: 0 PID: 19440 Comm: rsync Not tainted 5.3.0-rc5-20190820-doflr+ #1
[327011.399309] RIP: 0010:skb_shift+0x63/0x430
[327011.399326] Code: bc 00 00 00 48 03 8f c0 00 00 00 f6 41 03 08 74 07 48 83 79 28 00 75 d0 8b 8e bc 00 00 00 48 03 8e c0 00 00 00 48 85 f6 74 0a <f6> 41 03 08 0f 85 09 03 00 00 49 89 fd 8b bf bc 00 00 00 41 89 d4
[327011.399407] RSP: 0000:ffffc900000039b0 EFLAGS: 00010286
[327011.399427] RAX: 00000000000005a0 RBX: ffff8880115fb800 RCX: fffe8880115152c0
[327011.399456] RDX: 00000000000005a0 RSI: ffff8880115fb800 RDI: ffff88801b0f2200
[327011.399485] RBP: ffffc900000039e8 R08: 0000000000070260 R09: 00000000000005a0
[327011.399515] R10: 00000000000005a0 R11: ffff8880115fb800 R12: 0000000000000000
[327011.399544] R13: 000000000ca599b0 R14: 0000000000000000 R15: ffff88801b0f2200
[327011.399581] FS:  00007f20c1b8bb80(0000) GS:ffff88801f200000(0000) knlGS:0000000000000000
[327011.399610] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[327011.399633] CR2: 00007ffac4c245cc CR3: 0000000005544000 CR4: 00000000000006f0
[327011.399663] Call Trace:
[327011.399675]  <IRQ>
[327011.399688]  tcp_sacktag_walk+0x2af/0x480
[327011.399705]  ? __alloc_skb+0x52/0x1d0
[327011.399721]  tcp_sacktag_write_queue+0x34d/0x820
[327011.399743]  ? xennet_tx_setup_grant+0xbd/0x140
[327011.399762]  tcp_ack+0xb8c/0x1230
[327011.399778]  ? gnttab_foreach_grant_in_range+0x83/0xf0
[327011.399799]  ? xennet_tx_setup_grant+0x140/0x140
[327011.399819]  ? xennet_make_txreqs+0x81/0xb0
[327011.399838]  tcp_rcv_established+0x14c/0x630
[327011.399860]  tcp_v4_do_rcv+0x129/0x1d0
[327011.399876]  tcp_v4_rcv+0xac9/0xcb0
[327011.399892]  ip_protocol_deliver_rcu+0x27/0x1b0
[327011.399912]  ip_local_deliver_finish+0x3f/0x50
[327011.399932]  ip_local_deliver+0x4d/0xe0
[327011.399957]  ? ip_protocol_deliver_rcu+0x1b0/0x1b0
[327011.399977]  ip_rcv+0x4c/0xd0
[327011.400312]  __netif_receive_skb_one_core+0x79/0x90
[327011.400347]  netif_receive_skb_internal+0x2a/0xa0
[327011.400367]  napi_gro_receive+0xe7/0x140
[327011.400384]  xennet_poll+0x9be/0xae0
[327011.400401]  net_rx_action+0x136/0x340
[327011.400419]  __do_softirq+0xdd/0x2cf
[327011.400437]  irq_exit+0x7a/0xa0
[327011.400454]  xen_evtchn_do_upcall+0x27/0x40
[327011.400474]  xen_hvm_callback_vector+0xf/0x20
[327011.400501]  </IRQ>
[327011.400514] RIP: 0033:0x5620499a31aa
[327011.400532] Code: 43 4c 0f b6 34 0e 8b 8b 80 00 00 00 d3 e7 89 f9 48 8b 7b 60 31 f1 23 4b 7c 48 8b 73 68 83 fd 07 89 4b 70 48 8d 0c 4e 0f b7 31 <66> 42 89 34 47 66 89 11 0f 84 88 01 00 00 8b 8b 90 00 00 00 8b 83
[327011.400606] RSP: 002b:00007ffe82874060 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff0c
[327011.400638] RAX: 0000000000001f7c RBX: 000056204a861190 RCX: 000056204a8cd986
[327011.400671] RDX: 000000000000e084 RSI: 0000000000000000 RDI: 000056204a8bae50
[327011.400703] RBP: 0000000000000000 R08: 0000000000006084 R09: 0000000000003fdf
[327011.400735] R10: 0000000000000000 R11: 0000000000000001 R12: 00005620499b9500
[327011.400769] R13: 000000000000206a R14: 00000000ffffffff R15: 000056204a861190
[327011.400802] Modules linked in:
[327011.400884] ---[ end trace 660afb6bf8586996 ]---
[327011.400910] RIP: 0010:skb_shift+0x63/0x430
[327011.400929] Code: bc 00 00 00 48 03 8f c0 00 00 00 f6 41 03 08 74 07 48 83 79 28 00 75 d0 8b 8e bc 00 00 00 48 03 8e c0 00 00 00 48 85 f6 74 0a <f6> 41 03 08 0f 85 09 03 00 00 49 89 fd 8b bf bc 00 00 00 41 89 d4
[327011.401012] RSP: 0000:ffffc900000039b0 EFLAGS: 00010286
[327011.401042] RAX: 00000000000005a0 RBX: ffff8880115fb800 RCX: fffe8880115152c0
[327011.401081] RDX: 00000000000005a0 RSI: ffff8880115fb800 RDI: ffff88801b0f2200
[327011.401116] RBP: ffffc900000039e8 R08: 0000000000070260 R09: 00000000000005a0
[327011.401157] R10: 00000000000005a0 R11: ffff8880115fb800 R12: 0000000000000000
[327011.401198] R13: 000000000ca599b0 R14: 0000000000000000 R15: ffff88801b0f2200
[327011.401244] FS:  00007f20c1b8bb80(0000) GS:ffff88801f200000(0000) knlGS:0000000000000000
[327011.401293] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[327011.404822] CR2: 00007ffac4c245cc CR3: 0000000005544000 CR4: 00000000000006f0
[327011.404866] Kernel panic - not syncing: Fatal exception in interrupt
[327011.405103] Kernel Offset: disabled