Date:   Thu, 14 Oct 2021 10:38:22 +0800
From:   Hao Sun <sunhao.th@...il.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>, syzkaller-bugs@...glegroups.com
Subject: Re: WARNING in __init_work

Hillf Danton <hdanton@...a.com> 于2021年9月7日周二 下午3:44写道：
>
> On Tue, 7 Sep 2021 09:22:03 +0800 Hao Sun wrote:
> > When using Healer to fuzz the latest Linux kernel, the following crash
> > was triggered.
> >
> > HEAD commit: 27151f177827 Merge tag 'perf-tools-for-v5.15-2021-09-04'
> > git tree: upstream
> > console output:
> > https://drive.google.com/file/d/1M5oyA_IcWSDB2XpnoX8SDmKJA3JhKltz/view?usp=sharing
> > kernel config: https://drive.google.com/file/d/1ZMVJ2vNe0EiIEeWNVyrGb7hBdOG5Uj3e/view?usp=sharing
> > C reproducer: https://drive.google.com/file/d/1AtDNXl8XEBfglKXsKsAH2NuXBcrp8Zp9/view?usp=sharing
> > Syzlang reproducer:
> > https://drive.google.com/file/d/1R_XD_cyMNS0Q_SGSqomRy_LIClOrd-gI/view?usp=sharing
> >
> > If you fix this issue, please add the following tag to the commit:
> > Reported-by: Hao Sun <sunhao.th@...il.com>
>
> Thanks for reporting it.
>
> >
> > ODEBUG: object ffffc9000073cda0 is NOT on stack ffffc90005f34000, but annotated.
> > ------------[ cut here ]------------
> > WARNING: CPU: 2 PID: 27648 at lib/debugobjects.c:548
> > debug_object_is_on_stack lib/debugobjects.c:545 [inline]
> > WARNING: CPU: 2 PID: 27648 at lib/debugobjects.c:548
> > __debug_object_init+0x224/0x520 lib/debugobjects.c:607
> > Modules linked in:
> > CPU: 2 PID: 27648 Comm: syz-executor Not tainted 5.14.0+ #13
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> > RIP: 0010:debug_object_is_on_stack lib/debugobjects.c:545 [inline]
> > RIP: 0010:__debug_object_init+0x224/0x520 lib/debugobjects.c:607
> > Code: 84 ca fe ff ff 83 c0 01 4c 89 f6 48 c7 c7 f8 b0 3c 85 89 05 7e
> > c2 56 06 65 48 8b 04 25 40 70 01 00 48 8b 50 20 e8 05 9b f5 01 <0f> 0b
> > e9 9e fe ff ff 89 05 87 4d e3 03 e9 c4 fe ff ff 48 c7 c7 e0
> > RSP: 0018:ffffc9000073ccf0 EFLAGS: 00010282
> > RAX: 0000000000000050 RBX: ffff88810cf2f398 RCX: 0000000000000100
> > RDX: 0000000000000000 RSI: ffffffff812cf85c RDI: 00000000ffffffff
> > RBP: ffffffff88868538 R08: 0000000000000000 R09: 0000000000000001
> > R10: ffffc9000073cc80 R11: 0000000000000005 R12: 0000000000000203
> > R13: 0000000000054450 R14: ffffc9000073cda0 R15: ffff88807dd264f0
> > FS:  0000000002ad0940(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000005061ec CR3: 0000000100da5000 CR4: 0000000000750ee0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > PKRU: 55555554
> > Call Trace:
> >  <IRQ>
> >  __init_work+0x3f/0x50 kernel/workqueue.c:519
> >  synchronize_rcu_expedited+0x26a/0x460 kernel/rcu/tree_exp.h:847
>
> Given wait_event() in synchronize_rcu_expedited(), it is no good to come
> in a rcu context.
>
> >  bdi_remove_from_list mm/backing-dev.c:938 [inline]
> >  bdi_unregister+0x97/0x270 mm/backing-dev.c:946
> >  release_bdi+0x4a/0x70 mm/backing-dev.c:968
> >  kref_put include/linux/kref.h:65 [inline]
> >  bdi_put+0x47/0x70 mm/backing-dev.c:976
> >  bdev_free_inode+0x59/0xc0 fs/block_dev.c:819
> >  i_callback+0x24/0x50 fs/inode.c:224
> >  rcu_do_batch kernel/rcu/tree.c:2508 [inline]
> >  rcu_core+0x2d6/0x9f0 kernel/rcu/tree.c:2743
> >  __do_softirq+0xe9/0x561 kernel/softirq.c:558
> >  invoke_softirq kernel/softirq.c:432 [inline]
> >  __irq_exit_rcu kernel/softirq.c:636 [inline]
> >  irq_exit_rcu+0xe2/0x100 kernel/softirq.c:648
> >  sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1097
> >  </IRQ>
> >  asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
> > RIP: 0010:__sanitizer_cov_trace_pc+0x37/0x60 kernel/kcov.c:197
> > Code: 65 48 8b 14 25 40 70 01 00 81 e1 00 01 00 00 a9 00 01 ff 00 74
> > 0e 85 c9 74 35 8b 82 34 15 00 00 85 c0 74 2b 8b 82 10 15 00 00 <83> f8
> > 02 75 20 48 8b 8a 18 15 00 00 8b 92 14 15 00 00 48 8b 01 48
> > RSP: 0018:ffffc90005f37b78 EFLAGS: 00000246
> > RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000000000
> > RDX: ffff888109448000 RSI: ffffffff8212a28c RDI: ffffc90005f37d30
> > RBP: 0000000000000006 R08: 0000000000000d40 R09: ffff8880165fc5e0
> > R10: ffffc90005f37cd0 R11: 0000000000000003 R12: 0000000000000375
> > R13: ffff888107597b40 R14: ffffc90005f37d30 R15: ffff8880174b0ea0
> >  tomoyo_domain_quota_is_ok+0xac/0x150 security/tomoyo/util.c:1092
> >  tomoyo_supervisor+0x228/0x7f0 security/tomoyo/common.c:2089
> >  tomoyo_audit_path_log security/tomoyo/file.c:168 [inline]
> >  tomoyo_path_permission+0xa0/0xf0 security/tomoyo/file.c:587
> >  tomoyo_path_perm+0x22f/0x2d0 security/tomoyo/file.c:838
> >  tomoyo_path_symlink+0x43/0x70 security/tomoyo/tomoyo.c:199
> >  security_path_symlink+0x48/0x80 security/security.c:1164
> >  do_symlinkat+0x75/0x120 fs/namei.c:4274
> >  __do_sys_symlink fs/namei.c:4301 [inline]
> >  __se_sys_symlink fs/namei.c:4299 [inline]
> >  __x64_sys_symlink+0x3a/0x40 fs/namei.c:4299
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x34/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x46a597
> > Code: 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66
> > 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 58 00 00 00 0f 05 <48> 3d
> > 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007ffd09085778 EFLAGS: 00000206 ORIG_RAX: 0000000000000058
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000046a597
> > RDX: 0000000000000000 RSI: 00000000004e40f9 RDI: 00007ffd09085810
> > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000014
> > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
> > R13: 0000000000000000 R14: 00007ffd09085810 R15: 00007ffd090857cc
> > ----------------
> > Code disassembly (best guess):
> >    0: 65 48 8b 14 25 40 70 mov    %gs:0x17040,%rdx
> >    7: 01 00
> >    9: 81 e1 00 01 00 00    and    $0x100,%ecx
> >    f: a9 00 01 ff 00        test   $0xff0100,%eax
> >   14: 74 0e                je     0x24
> >   16: 85 c9                test   %ecx,%ecx
> >   18: 74 35                je     0x4f
> >   1a: 8b 82 34 15 00 00    mov    0x1534(%rdx),%eax
> >   20: 85 c0                test   %eax,%eax
> >   22: 74 2b                je     0x4f
> >   24: 8b 82 10 15 00 00    mov    0x1510(%rdx),%eax
> > * 2a: 83 f8 02              cmp    $0x2,%eax <-- trapping instruction
> >   2d: 75 20                jne    0x4f
> >   2f: 48 8b 8a 18 15 00 00 mov    0x1518(%rdx),%rcx
> >   36: 8b 92 14 15 00 00    mov    0x1514(%rdx),%edx
> >   3c: 48 8b 01              mov    (%rcx),%rax
> >   3f: 48                    rex.W%
> >
>
> Move releasing of bdi to workqueue work to make it safe to sync rcu.
>
> Only for thoughts now.
>
> +++ x/mm/backing-dev.c
> @@ -959,10 +959,11 @@ void bdi_unregister(struct backing_dev_i
>         }
>  }
>
> -static void release_bdi(struct kref *ref)
> +static void bdi_release_workfn(struct work_struct *work)
>  {
> -       struct backing_dev_info *bdi =
> -                       container_of(ref, struct backing_dev_info, refcnt);
> +       struct backing_dev_info *bdi;
> +
> +       bdi = container_of(work, struct backing_dev_info, release_work);
>
>         if (test_bit(WB_registered, &bdi->wb.state))
>                 bdi_unregister(bdi);
> @@ -971,6 +972,16 @@ static void release_bdi(struct kref *ref
>         kfree(bdi);
>  }
>
> +static void release_bdi(struct kref *ref)
> +{
> +       struct backing_dev_info *bdi;
> +
> +       bdi = container_of(ref, struct backing_dev_info, refcnt);
> +
> +       INIT_WORK(&bdi->release_work, bdi_release_workfn);
> +       queue_work(system_unbound_wq, &bdi->release_work);
> +}
> +
>  void bdi_put(struct backing_dev_info *bdi)
>  {
>         kref_put(&bdi->refcnt, release_bdi);

Hi,

This issue can still be triggered repeatedly on the latest Linux kernel.

HEAD commit: 64570fbc14f8 Linux 5.15-rc5
git tree: upstream
kernel config: https://drive.google.com/file/d/1em3xgUIMNN_-LUUdySzwN-UDPc3qiiKD/view?usp=sharing

ODEBUG: object ffffc90000007bc0 is NOT on stack ffffffff8b600000, but annotated.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at lib/debugobjects.c:548
debug_object_is_on_stack lib/debugobjects.c:542 [inline]
WARNING: CPU: 0 PID: 0 at lib/debugobjects.c:548
__debug_object_init.cold+0x21d/0x29a lib/debugobjects.c:607
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.0-rc5 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:debug_object_is_on_stack lib/debugobjects.c:548 [inline]
RIP: 0010:__debug_object_init.cold+0x21d/0x29a lib/debugobjects.c:607
Code: 00 48 8d 7b 20 48 89 fa 48 c1 ea 03 80 3c 02 00 74 05 e8 2a 7d
be f8 48 8b 53 20 4c 89 e6 48 c7 c7 80 3b e4 89 e8 22 42 f2 ff <0f> 0b
e9 cf bc e6 fa 4c 89 e0 48 c1 e8 03 80 3c 18 00 74 08 4c 89
RSP: 0018:ffffc900000079f0 EFLAGS: 00010282
RAX: 0000000000000050 RBX: ffffffff8b6bc640 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8b6bc640 RDI: fffff52000000f30
RBP: ffffffff8b6bc640 R08: 0000000000000050 R09: 0000000000000000
R10: 0000000000000005 R11: ffffed100c7c57f8 R12: ffffc90000007bc0
R13: 1ffff92000000f4c R14: ffffffff90472c30 R15: ffffffff90472c38
FS:  0000000000000000(0000) GS:ffff888063e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555556100c48 CR3: 00000000279c8000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 __init_work+0x2d/0x50 kernel/workqueue.c:519
 synchronize_rcu_expedited+0x3af/0x650 kernel/rcu/tree_exp.h:847
 bdi_remove_from_list mm/backing-dev.c:938 [inline]
 bdi_unregister+0x17f/0x5c0 mm/backing-dev.c:946
 release_bdi+0xa1/0xc0 mm/backing-dev.c:968
 kref_put include/linux/kref.h:65 [inline]
 bdi_put+0x72/0xa0 mm/backing-dev.c:976
 bdev_free_inode+0x11e/0x220 block/bdev.c:408
 i_callback+0x3f/0x70 fs/inode.c:226
 rcu_do_batch kernel/rcu/tree.c:2508 [inline]
 rcu_core+0x76d/0x16c0 kernel/rcu/tree.c:2743
 __do_softirq+0x1d7/0x93b kernel/softirq.c:558
 invoke_softirq kernel/softirq.c:432 [inline]
 __irq_exit_rcu kernel/softirq.c:636 [inline]
 irq_exit_rcu+0xf2/0x130 kernel/softirq.c:648
 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1097
 </IRQ>
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:717
Code: 1b 51 88 f8 e9 6f fe ff ff e8 11 51 88 f8 e9 3d fe ff ff e8 17
31 fd ff cc cc cc cc cc cc cc eb 07 0f 00 2d 47 99 50 00 fb f4 <c3> 0f
1f 40 00 41 54 be 08 00 00 00 53 65 48 8b 1c 25 40 f0 01 00
RSP: 0018:ffffffff8b607e28 EFLAGS: 00000206
RAX: 000000000006117b RBX: 0000000000000000 RCX: ffffffff8932d572
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed100c7c6542
R10: ffff888063e32a0b R11: ffffed100c7c6541 R12: 0000000000000000
R13: 0000000000000000 R14: ffffffff8d6d8590 R15: 0000000000000000
 default_idle_call+0xc4/0x420 kernel/sched/idle.c:112
 cpuidle_idle_call kernel/sched/idle.c:194 [inline]
 do_idle+0x3f9/0x570 kernel/sched/idle.c:306
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403
 start_kernel+0x47a/0x49b init/main.c:1141
 secondary_startup_64_no_verify+0xb0/0xbb
----------------
Code disassembly (best guess):
   0: 1b 51 88              sbb    -0x78(%rcx),%edx
   3: f8                    clc
   4: e9 6f fe ff ff        jmpq   0xfffffe78
   9: e8 11 51 88 f8        callq  0xf888511f
   e: e9 3d fe ff ff        jmpq   0xfffffe50
  13: e8 17 31 fd ff        callq  0xfffd312f
  18: cc                    int3
  19: cc                    int3
  1a: cc                    int3
  1b: cc                    int3
  1c: cc                    int3
  1d: cc                    int3
  1e: cc                    int3
  1f: eb 07                jmp    0x28
  21: 0f 00 2d 47 99 50 00 verw   0x509947(%rip)        # 0x50996f
  28: fb                    sti
  29: f4                    hlt
* 2a: c3                    retq <-- trapping instruction
  2b: 0f 1f 40 00          nopl   0x0(%rax)
  2f: 41 54                push   %r12
  31: be 08 00 00 00        mov    $0x8,%esi
  36: 53                    push   %rbx
  37: 65 48 8b 1c 25 40 f0 mov    %gs:0x1f040,%rbx
  3e: 01 00%

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