Re: [bugreport 5.9-rc8] general protection fault, probably for non-canonical address 0x46b1b0f0d8856e4a: 0000 [#1] SMP NOPTI

[Ming Lei <ming.lei@redhat.com>]

On Fri, Mar 05, 2021 at 10:32:04AM +0100, Paolo Valente wrote:
> I'm thinking of a way to debug this too.  The symptom may hint at a
> use-after-free.  Could you enable KASAN in your tests?  (On the flip
> side, I know this might change timings, thereby making the fault
> disappear).

I have asked our QE to reproduce the issue with debug kernel, which may take a
while. And I can't trigger it in my box.

BTW, for the 2nd 'kernel NULL pointer dereference', the RIP points to:

(gdb) l *(__bfq_deactivate_entity+0x5b)
0xffffffff814c31cb is in __bfq_deactivate_entity (block/bfq-wf2q.c:1181).
1176		 * bfq_group_set_parent has already been invoked for the group
1177		 * represented by entity. Therefore, the field
1178		 * entity->sched_data has been set, and we can safely use it.
1179		 */
1180		st = bfq_entity_service_tree(entity);
1181		is_in_service = entity == sd->in_service_entity;
1182
1183		bfq_calc_finish(entity, entity->service);
1184
1185		if (is_in_service)

Seems entity->sched_data points to NULL.


> 
> Thanks,
> Paolo
> 
> > Il giorno 5 mar 2021, alle ore 10:27, Ming Lei <tom.leiming@gmail.com> ha scritto:
> > 
> > Hello Hillf,
> > 
> > Thanks for the debug patch.
> > 
> > On Fri, Mar 5, 2021 at 5:00 PM Hillf Danton <hdanton@sina.com> wrote:
> >> 
> >> On Thu, 4 Mar 2021 16:42:30 +0800  Ming Lei wrote:
> >>> On Sat, Oct 10, 2020 at 1:40 PM Mikhail Gavrilov
> >>> <mikhail.v.gavrilov@gmail.com> wrote:
> >>>> 
> >>>> Paolo, Jens I am sorry for the noise.
> >>>> But today I hit the kernel panic and git blame said that you have
> >>>> created the file in which happened panic (this I saw from trace)
> >>>> 
> >>>> $ /usr/src/kernels/`uname -r`/scripts/faddr2line
> >>>> /lib/debug/lib/modules/`uname -r`/vmlinux
> >>>> __bfq_deactivate_entity+0x15a
> >>>> __bfq_deactivate_entity+0x15a/0x240:
> >>>> bfq_gt at block/bfq-wf2q.c:20
> >>>> (inlined by) bfq_insert at block/bfq-wf2q.c:381
> >>>> (inlined by) bfq_idle_insert at block/bfq-wf2q.c:621
> >>>> (inlined by) __bfq_deactivate_entity at block/bfq-wf2q.c:1203
> >>>> 
> >>>> https://github.com/torvalds/linux/blame/master/block/bfq-wf2q.c#L1203
> >>>> 
> >>>> $ head /sys/block/*/queue/scheduler
> >>>> ==> /sys/block/nvme0n1/queue/scheduler <==
> >>>> [none] mq-deadline kyber bfq
> >>>> 
> >>>> ==> /sys/block/sda/queue/scheduler <==
> >>>> mq-deadline kyber [bfq] none
> >>>> 
> >>>> ==> /sys/block/zram0/queue/scheduler <==
> >>>> none
> >>>> 
> >>>> Trace:
> >>>> general protection fault, probably for non-canonical address
> >>>> 0x46b1b0f0d8856e4a: 0000 [#1] SMP NOPTI
> >>>> CPU: 27 PID: 1018 Comm: kworker/27:1H Tainted: G        W
> >>>> --------- ---  5.9.0-0.rc8.28.fc34.x86_64 #1
> >>>> Hardware name: System manufacturer System Product Name/ROG STRIX
> >>>> X570-I GAMING, BIOS 2606 08/13/2020
> >>>> Workqueue: kblockd blk_mq_run_work_fn
> >>>> RIP: 0010:__bfq_deactivate_entity+0x15a/0x240
> >>>> Code: 48 2b 41 28 48 85 c0 7e 05 49 89 5c 24 18 49 8b 44 24 08 4d 8d
> >>>> 74 24 08 48 85 c0 0f 84 d6 00 00 00 48 8b 7b 28 eb 03 48 89 c8 <48> 8b
> >>>> 48 28 48 8d 70 10 48 8d 50 08 48 29 f9 48 85 c9 48 0f 4f d6
> >>>> RSP: 0018:ffffadf6c0c6fc00 EFLAGS: 00010002
> >>>> RAX: 46b1b0f0d8856e4a RBX: ffff8dc2773b5c88 RCX: 46b1b0f0d8856e4a
> >>>> RDX: ffff8dc7d02ed0a0 RSI: ffff8dc7d02ed0a8 RDI: 0000584e64e96beb
> >>>> RBP: ffff8dc2773b5c00 R08: ffff8dc9054cb938 R09: 0000000000000000
> >>>> R10: 0000000000000018 R11: 0000000000000018 R12: ffff8dc904927150
> >>>> R13: 0000000000000001 R14: ffff8dc904927158 R15: ffff8dc2773b5c88
> >>>> FS:  0000000000000000(0000) GS:ffff8dc90e0c0000(0000) knlGS:0000000000000000
> >>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>> CR2: 0000003e8ebe4000 CR3: 00000007c2546000 CR4: 0000000000350ee0
> >>>> Call Trace:
> >>>> bfq_deactivate_entity+0x4f/0xc0
> >>> 
> >>> Hello,
> >>> 
> >>> The same stack trace was observed in RH internal test too, and kernel
> >>> is 5.11.0-0.rc6,
> >>> but there isn't reproducer yet.
> >>> 
> >>> 
> >>> --
> >>> Ming Lei
> >> 
> >> Add some debug info.
> >> 
> >> --- x/block/bfq-wf2q.c
> >> +++ y/block/bfq-wf2q.c
> >> @@ -647,8 +647,10 @@ static void bfq_forget_entity(struct bfq
> >> 
> >>        entity->on_st_or_in_serv = false;
> >>        st->wsum -= entity->weight;
> >> -       if (bfqq && !is_in_service)
> >> +       if (bfqq && !is_in_service) {
> >> +               WARN_ON(entity->tree != NULL);
> >>                bfq_put_queue(bfqq);
> >> +       }
> >> }
> >> 
> >> /**
> >> @@ -1631,6 +1633,7 @@ bool __bfq_bfqd_reset_in_service(struct
> >>                 * bfqq gets freed here.
> >>                 */
> >>                int ref = in_serv_bfqq->ref;
> >> +               WARN_ON(in_serv_entity->tree != NULL);
> >>                bfq_put_queue(in_serv_bfqq);
> >>                if (ref == 1)
> >>                        return true;
> > 
> > This kernel oops isn't easy to be reproduced, and  we have got another crash
> > report[1] too, still on __bfq_deactivate_entity(), and not easy to
> > trigger.  Can your
> > debug patch cover the report[1]? If not, feel free to add more debug messages,
> > then I will try to reproduce the two.
> > 
> > [1] another kernel oops log on __bfq_deactivate_entity
> > 
> > [  899.790606] systemd-sysv-generator[25205]: SysV service
> > '/etc/rc.d/init.d/anamon' lacks a native systemd unit file.
> > Automatically generating a unit file for compatibility. Please update
> > package to include a native systemd unit file, in order to make it
> > more safe and robust.
> > [  901.937047] BUG: kernel NULL pointer dereference, address: 0000000000000000
> > [  901.944005] #PF: supervisor read access in kernel mode
> > [  901.949143] #PF: error_code(0x0000) - not-present page
> > [  901.954285] PGD 0 P4D 0
> > [  901.956824] Oops: 0000 [#1] SMP NOPTI
> > [  901.960490] CPU: 13 PID: 22966 Comm: kworker/13:0 Tainted: G
> >  I    X --------- ---  5.11.0-1.el9.x86_64 #1
> > [  901.970829] Hardware name: Dell Inc. PowerEdge R740xd/0WXD1Y, BIOS
> > 2.5.4 01/13/2020
> > [  901.978480] Workqueue: cgwb_release cgwb_release_workfn
> > [  901.983705] RIP: 0010:__bfq_deactivate_entity+0x5b/0x240
> > [  901.989016] Code: b8 30 00 00 00 75 18 48 81 ff 88 00 00 00 74 0f
> > 0f b7 47 8a 83 e8 01 48 8d 04 40 48 c1 e0 04 4c 8b 73 68 48 63 73 40
> > 48 89 df <4d> 8b 3e 4d 8d 64 06 10 e8 48 f0 ff ff 49 39 df 0f 84 87 01
> > 00 00
> > [  902.007763] RSP: 0018:ffffb77107f0bd98 EFLAGS: 00010002
> > [  902.012986] RAX: 0000002fffffffd0 RBX: ffff9853ca9c6098 RCX: 0000000000000046
> > [  902.020119] RDX: 0000000000000001 RSI: 00000000474b1168 RDI: ffff9853ca9c6098
> > [  902.027253] RBP: 0000000000000000 R08: 0000000000000000 R09: ffff985470c2fed0
> > [  902.034383] R10: 0000000000000001 R11: ffff9853c9287d98 R12: ffff9853ca8b8000
> > [  902.041515] R13: 00000000000000ff R14: 0000000000000000 R15: ffff985b44308098
> > [  902.048647] FS:  0000000000000000(0000) GS:ffff98631f980000(0000)
> > knlGS:0000000000000000
> > [  902.056732] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [  902.062479] CR2: 0000000000000000 CR3: 00000001c0ac2002 CR4: 00000000007706e0
> > [  902.069611] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > [  902.076744] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > [  902.083876] PKRU: 55555554
> > [  902.086589] Call Trace:
> > [  902.089042]  bfq_pd_offline+0x89/0xd0
> > [  902.092708]  blkg_destroy+0x52/0xf0
> > [  902.096200]  blkcg_destroy_blkgs+0x46/0xc0
> > [  902.100300]  cgwb_release_workfn+0xbe/0x150
> > [  902.104485]  process_one_work+0x1e6/0x380
> > [  902.108497]  worker_thread+0x53/0x3d0
> > [  902.112161]  ? process_one_work+0x380/0x380
> > [  902.116346]  kthread+0x11b/0x140
> > [  902.119581]  ? kthread_associate_blkcg+0xa0/0xa0
> > [  902.124199]  ret_from_fork+0x1f/0x30
> > [  902.127780] Modules linked in: sunrpc scsi_debug iscsi_tcp
> > libiscsi_tcp libiscsi scsi_transport_iscsi nft_reject_inet
> > nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat
> > nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink
> > rfkill intel_rapl_msr intel_rapl_common isst_if_common skx_edac nfit
> > libnvdimm x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm
> > ipmi_ssif irqbypass mgag200 rapl i2c_algo_bit iTCO_wdt drm_kms_helper
> > intel_cstate iTCO_vendor_support syscopyarea sysfillrect sysimgblt
> > acpi_ipmi mei_me fb_sys_fops intel_uncore pcspkr dell_smbios dcdbas
> > dell_wmi_descriptor wmi_bmof mei cec i2c_i801 ipmi_si acpi_power_meter
> > lpc_ich i2c_smbus ipmi_devintf ipmi_msghandler drm fuse xfs libcrc32c
> > sd_mod t10_pi crct10dif_pclmul crc32_pclmul crc32c_intel ahci libahci
> > megaraid_sas tg3 ghash_clmulni_intel libata wmi dm_mirror
> > dm_region_hash dm_log dm_mod [last unloaded: ip_tables]
> > [  902.208546] CR2: 0000000000000000
> > [  902.211881] ---[ end trace 827b8521dc634ca4 ]---
> > 
> > 
> > -- 
> > Ming Lei
> 

-- 
Ming