uml segfault during I/O

From: Ritesh Raj Sarraf <rrs@researchut.com>
To: linux-um@lists.infradead.org
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Subject: uml segfault during I/O
Date: Thu, 17 Oct 2019 17:07:35 +0530	[thread overview]
Message-ID: <a1307b17bd3f51d84d9195760492d1ef284b6382.camel@researchut.com> (raw)

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This happens on the 5.2 Linux kernel with Debian patches on top.
The configs details are:

Linux Host: 5.2 (Debian)
Linux UML: 5.2 (Debian)

This tends to happen very easily when doing good amount of I/O, in this
case, doing an `apt upgrade`

[  OK  ] Started Update UTMP about System Runlevel Changes.
NET: Registered protocol family 10
Segment Routing with IPv6
random: crng init done

Modules linked in: ipv6 crc_ccitt
Pid: 870, comm: kworker/0:1H Not tainted 5.2.17
RIP: 0033:[<00000000607e9c03>]
RSP: 000000009d40fde0  EFLAGS: 00010297
RAX: 0000000000000000 RBX: 0000000000004801 RCX: 000000009d40fe30
RDX: 0000000000000001 RSI: 000000009dbc35c0 RDI: 0000000000000000
RBP: 000000009d40fe30 R08: 0000000c00000204 R09: 8080808080808080
R10: fefefefefefefeff R11: 0000000000000246 R12: 0000000000000000
R13: 000000009dbc35c0 R14: 000000009dbc3608 R15: 000000009dbb9800
Kernel panic - not syncing: Segfault with no mm
CPU: 0 PID: 870 Comm: kworker/0:1H Not tainted 5.2.17 #2
Workqueue: kblockd blk_mq_requeue_work
Stack:
 00000000 100000000000001 607d4425 00000001
 9dbc35c0 00000000 00000000 00000000
 9dbb9800 607d44e9 9d40fe30 9d40fe30
Call Trace:
 [<607d4425>] ? blk_mq_sched_insert_request+0x0/0xff
 [<607d44e9>] ? blk_mq_sched_insert_request+0xc4/0xff
 [<607d4425>] ? blk_mq_sched_insert_request+0x0/0xff
 [<607d07c6>] ? blk_mq_requeue_work+0xd0/0x133
 [<60434285>] ? process_one_work+0x1e4/0x34c
 [<60431fd0>] ? move_linked_works+0x0/0x4f
 [<609791f0>] ? __schedule+0x0/0x41d
 [<6043569f>] ? wq_worker_running+0xd/0x2f
 [<60431fd0>] ? move_linked_works+0x0/0x4f
 [<60435362>] ? worker_thread+0x324/0x45e
 [<6043215f>] ? set_pf_worker+0x0/0x5e
 [<604167c7>] ? get_signals+0x0/0xa
 [<60439485>] ? __kthread_parkme+0x4a/0x94
 [<60421a53>] ? do_exit+0x0/0x948
 [<6043503e>] ? worker_thread+0x0/0x45e
 [<604399aa>] ? kthread+0x198/0x1a0
 [<603fea08>] ? new_thread_handler+0x82/0xb8

/home/rrs/bin/uml-debian: line 8: 16743 Aborted                 (core dumped) linux ubd0=~/rrs-home/Libvirt-Images/uml.img eth0=daemon mem=1024M rw
 16:58 ♒ ॐ   ☹ 😟=> 134  

And the linux process remains stray on the host machine.

rrs      18159  0.0  0.0 1057692 11496 ?       Ss   16:57   0:00 linux ubd0=/home/rrs/rrs-home/Libvirt-Images/uml.img eth0=daemon mem=1024M rw
rrs      18187  0.0  0.0 1057704 11496 ?       Ss   16:57   0:00 linux ubd0=/home/rrs/rrs-home/Libvirt-Images/uml.img eth0=daemon mem=1024M rw

-- 
Ritesh Raj Sarraf
RESEARCHUT - http://www.researchut.com
"Necessity is the mother of invention."

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