bfq_deactivate_entity: NULL pointer dereference

[Sergey Borodavkin]

Hello. We meet a kernel panic with next trace:

bfq_insert+0x5c/0x70 [bfq]
__bfq_deactivate_entity+0xe7/0x1b0 [bfq]
bfq_deactivate_entity+0x5d/0xd0 [bfq]
bfq_del_bfqq_busy+0xac/0x150 [bfq]
__bfq_bfqq_expire+0x64/0xd0 [bfq]
bfq_bfqq_expire+0x331/0x930 [bfq]
? try_to_wake_up+0x235/0x5f0
? bfq_dispatch_request+0xf70/0xf70 [bfq]
bfq_idle_slice_timer+0x6d/0xc0 [bfq]
__hrtimer_run_queues+0x10f/0x280
hrtimer_interrupt+0xe7/0x230
smp_apic_timer_interrupt+0x6f/0x130
apic_timer_interrupt+0xf/0x20

After little research i found out that bug was reported by Fedora and openSUSE community earlier.
https://bugzilla.redhat.com/show_bug.cgi?id=2022819
https://bugzilla.opensuse.org/show_bug.cgi?id=1192714

And patch for this bug already exist
https://<email address hidden>/

Since there are no similar reports in the Ubuntu community, I decided to make this report.
Full dmesg log in attachments.
Also have a crash dump file, can attach that file if it necessary.

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Environment:
  Distributor ID: Ubuntu
  Description: Ubuntu 18.04.6 LTS
  Release: 18.04
  Codename: bionic
  kernel: 5.4.0-110-generic #124~18.04.1-Ubuntu

[Sergey Borodavkin (bocmanpy)]

Hi.
Problem still appear on 5.4.0-125 kernel version.

[alexey (postdespodency)]

Hello!
Problem still appear on 5.4.0-150 kernel version!