Ubuntu
linux-hwe-5.13 package

BUG:soft lockup - CPU#0 stuck for 36s! rcu_core_si kernel/rcu/tree.c:2807

Bug #1983436 reported by saltf1sh on 2022-08-03

264

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	linux-hwe-5.13 (Ubuntu)	New	Undecided	Unassigned
	linux-hwe-5.15 (Ubuntu)	New	Undecided	Unassigned

Bug Description

We would like to report the following bug which has been found by our modified version of syzkaller.
rcu_core_si in kernel/rcu/tree.c:2807 in the Linux kernel through 5.13 allows attackers to cause a denial of service (soft lockup) via a large number of different function calls.
description: BUG: soft lockup in rcu_core_si
affected file: kernel/rcu/tree.c
kernel version: 5.13
kernel config, syzkaller reproducer and raw console output are all in the attachments.
======================================================
Crash log:
======================================================
watchdog: BUG: soft lockup - CPU#0 stuck for 36s! [syz-executor.6:14479]
Modules linked in:
CPU: 0 PID: 14479 Comm: syz-executor.6 Not tainted 5.13.19+ #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:cred_label security/apparmor/include/cred.h:27 [inline]
RIP: 0010:apparmor_cred_free+0x5f/0x1a0 security/apparmor/lsm.c:69
Code: 01 00 00 48 63 1d a1 fd 4d 02 49 03 5c 24 78 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 80 3c 02 00 0f 85 08 01 00 00 <4c> 8b 2b 4d 85 ed 74 68 e8 74 53 4b ff be 04 00 00 00 4c 89 ef bb
RSP: 0018:ffff888056609dc8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff888005c8fc80 RCX: ffffffff967eb4fd
RDX: 1ffff11000b91f90 RSI: 0000000000000100 RDI: ffff888005821000
RBP: ffff888056609de8 R08: 0000000000000001 R09: ffffed1000b04201
R10: ffff888005821003 R11: ffffed1000b04200 R12: ffff888005821000
R13: ffff888005821000 R14: ffff888005821078 R15: ffff888007ba8000
FS: 00007f5f81a40700(0000) GS:ffff888056600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe8252bb80 CR3: 0000000003cf6006 CR4: 0000000000770ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<IRQ>
security_cred_free+0x83/0x130 security/security.c:1881
put_cred_rcu+0x71/0x360 kernel/cred.c:115
rcu_do_batch kernel/rcu/tree.c:2559 [inline]
rcu_core+0x536/0x12f0 kernel/rcu/tree.c:2794
rcu_core_si+0xe/0x10 kernel/rcu/tree.c:2807
__do_softirq+0x187/0x576 kernel/softirq.c:559
invoke_softirq kernel/softirq.c:433 [inline]
__irq_exit_rcu kernel/softirq.c:637 [inline]
irq_exit_rcu+0x120/0x150 kernel/softirq.c:649
sysvec_apic_timer_interrupt+0x79/0x90 arch/x86/kernel/apic/apic.c:1100
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:0xffffffffc01e0801
Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 0f 1f 44 00 00 <55> 48 89 e5 53 41 55 31 c0 45 31 ed 48 89 fb b8 ff ff ff 7f 41 5d
RSP: 0018:ffff888006ec7d58 EFLAGS: 00000246
RAX: ffffffffc01e07fc RBX: 000000007fff0000 RCX: ffffffff95ccef6a
RDX: ffff888007ba8000 RSI: ffffc90000763048 RDI: ffff888006ec7e10
RBP: ffff888006ec7eb8 R08: 0000000000000001 R09: ffffed1005374c87
R10: ffff888029ba6437 R11: ffffed1005374c86 R12: ffff888006ec7e10
R13: ffff888029ba6400 R14: ffffc90000763000 R15: dffffc0000000000
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted 5.13.19+ #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
RIP: 0010:watchdog+0x1e1/0xa60 kernel/hung_task.c:294
Code: 45 a8 e8 e2 74 fd ff 49 8d 87 40 03 00 00 48 b9 00 00 00 00 00 fc ff df 48 89 45 c0 48 c1 e8 03 80 3c 08 00 0f 85 dd 07 00 00 <49> 8b 9f 40 03 00 00 48 be 00 00 00 00 00 fc ff df 4c 8d 63 10 4c
RSP: 0000:ffff888001d77ea0 EFLAGS: 00010246
RAX: 1ffff11000dea98b RBX: ffff88800669b630 RCX: dffffc0000000000
RDX: ffff888001d6a080 RSI: 0000000000000000 RDI: ffff888005e4c918
RBP: ffff888001d77f00 R08: 0000000000000001 R09: fffffbfff34354d9
R10: ffffffff9a1aa6c7 R11: fffffbfff34354d8 R12: ffff88800669c010
R13: 00000000003fff85 R14: 0000000100021a4b R15: ffff888006f54918
FS: 0000000000000000(0000) GS:ffff888056700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcc3c83ce8 CR3: 0000000004310004 CR4: 0000000000770ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
kthread+0x352/0x430 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
</TASK>
----------------
Code disassembly (best guess):
   0: 01 00 add %eax,(%rax)
   2: 00 48 63 add %cl,0x63(%rax)
   5: 1d a1 fd 4d 02 sbb $0x24dfda1,%eax
   a: 49 03 5c 24 78 add 0x78(%r12),%rbx
   f: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
  16: fc ff df
  19: 48 89 da mov %rbx,%rdx
  1c: 48 c1 ea 03 shr $0x3,%rdx
  20: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
  24: 0f 85 08 01 00 00 jne 0x132
* 2a: 4c 8b 2b mov (%rbx),%r13 <-- trapping instruction
  2d: 4d 85 ed test %r13,%r13
  30: 74 68 je 0x9a
  32: e8 74 53 4b ff callq 0xff4b53ab
  37: be 04 00 00 00 mov $0x4,%esi
  3c: 4c 89 ef mov %r13,%rdi
  3f: bb .byte 0xbb
--

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Revision history for this message

saltf1sh (saltf1sh) wrote on 2022-08-03:

syzkaller reproducer Edit (518 bytes, text/plain)

Revision history for this message

saltf1sh (saltf1sh) wrote on 2022-08-03:

kernel config Edit (262.0 KiB, text/plain)

Revision history for this message

saltf1sh (saltf1sh) wrote on 2022-08-03:

raw console output Edit (9.0 KiB, text/html)

affects:

linux (Ubuntu) → linux-hwe-5.13 (Ubuntu)

saltf1sh (saltf1sh) on 2022-08-04

information type:

Private Security → Public Security

Revision history for this message

Simon Déziel (sdeziel) wrote on 2022-08-24:

@saltf1sh, thanks for reporting this, however, the 5.13 kernel is no longer supported (since July 2022). Are you able to reproduce the problem on a kernel version that's still supported (like 5.4 or 5.15)?

Revision history for this message

saltf1sh (saltf1sh) wrote on 2022-08-25:

Download full text (9.3 KiB)

@sdeziel,thanks for your prompt. Today I have reproduced the bug in kernel version 5.4 and kernel version 5.15 respectively. The experiment proves that the bug still exists.
I use this command:
"./syz-execprog -executor=./syz-executor -repeat=0 -procs=8 -cover=0 -threaded=0 -collide=0 ./SyzReproRcu".
Crash can still be triggered in the kernel.
You can download CReproducerRcu.c. Locally through "gcc CReproducerRcu.c -o CReproducerRcu" gets the file CReproducerRcu. Run "./CReproducerRcu" locally and wait for about one minute. You can see the message "rcu: INFO: rcu_sched self-detected stall on CPU". I'm not sure if this is a bug.
You can use vm_5dot4.log and vm_5dot15.log to view each step of my operation in QEMU. According to stack trace, the problem may be rcu_sched_clock_irq? I'm not sure which file in the kernel corresponds to the bug.
======================================================
The following are links related to kernel 5.4:
Description: rcu: INFO: rcu_sched self-detected stall on CPU
Kernel version: 5.4
Kernel config: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.4/.config
C reproducer: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.4/CReproducerRcu.c
Crash log: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.4/CrashLog.txt
Syz repro: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.4/SyzReproRcu
Vm.log: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.4/vm_5dot4.log

Crash log:
[   65.129421] audit: type=1400 audit(1661428172.369:15): avc:  denied  { execmem } for  pid=360 comm="CReproducerRcu" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=process permissive=1
[   79.840127] hrtimer: interrupt took 14052 ns
[  104.359596] rcu: INFO: rcu_sched self-detected stall on CPU
[  104.368030] rcu: 	0-....: (20995 ticks this GP) idle=eee/1/0x4000000000000004 softirq=3077/3077 fqs=4694 
[  104.373374] 	(t=21000 jiffies g=4473 q=220481)
[  104.375926] NMI backtrace for cpu 0
[  104.378133] CPU: 0 PID: 12886 Comm: CReproducerRcu Not tainted 5.4.192 #1
[  104.381887] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[  104.387042] Call Trace:
[  104.388557]  <IRQ>
[  104.390225]  dump_stack+0x95/0xc8
[  104.392112]  nmi_cpu_backtrace.cold+0x55/0x94
[  104.394758]  ? lapic_can_unplug_cpu+0x70/0x70
[  104.397442]  nmi_trigger_cpumask_backtrace+0x15a/0x1b0
[  104.400354]  rcu_dump_cpu_stacks+0x15d/0x1a7
[  104.402749]  rcu_sched_clock_irq.cold+0x4c8/0x90b
[  104.405510]  ? hrtimer_run_queues+0x1d/0x310
[  104.407876]  update_process_times+0x24/0x60
[  104.410279]  tick_sched_handle+0x10f/0x150
[  104.412622]  tick_sched_timer+0x41/0x120
[  104.414804]  __hrtimer_run_queues+0x308/0x7c0
[  104.417218]  ? tick_sched_do_timer+0x160/0x160
[  104.419750]  ? enqueue_hrtimer+0x230/0x230
[  104.422074]  ? kvm_clock_get_cycles+0xd/0x10
[  104.424437]  ? ktime_get_update_offsets_now+0x17d/0x250
[  104.427363]  hrtimer_interrupt+0x2c9/0x6c0
[  104.429693]  smp_apic_timer_interrupt+0xd4/0x380
[  104.432226]  apic_timer_interrupt+0xf/0x20
[  104.434517] RIP: 0010:clocksource_watchdog+0xa/0x8b0
[  104.437264] Code: 48 c7 c7 48 ed 37 bd e8 34 11 2e 00 e9 74 ff ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 41 57 41 56 41 55 41 54 55 53 <48> 83 ec 50 e8 9d 30 0b 00 48 c7 c7 40 7d ca bd e8 91 e5 22 02 8b
[  104.447427] RSP: 0018:ffff88806d209d88 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
[  104.451622] RAX: ffffffffb9e945c0 RBX: ffff88806d209e80 RCX: ffffffffb9e7fe19
[  104.455952] RDX: 0000000000000100 RSI: ffffffffb9e945c0 RDI: ffffffffbdca7d80
[  104.460191] RBP: 0000000000000100 R08: 0000000000000001 R09: ffffed100da45aae
[  104.464058] R10: ffffed100da45aad R11: ffff88806d22d56f R12: ffffffffbdca7d80
[  104.467990] R13: 00000000fffcaa29 R14: 00000000fffcaa29 R15: ffff88806d22d540
[  104.471933]  ? apic_timer_interrupt+0xa/0x20
[  104.474346]  ? __clocksource_unstable+0x170/0x170
[  104.476956]  ? call_timer_fn+0x39/0x2b0
[  104.479082]  ? __clocksource_unstable+0x170/0x170
[  104.481732]  call_timer_fn+0x45/0x2b0
[  104.483781]  ? __clocksource_unstable+0x170/0x170
[  104.486381]  ? __clocksource_unstable+0x170/0x170
[  104.488998]  run_timer_softirq+0x53b/0x1230
[  104.491289]  ? call_timer_fn+0x2b0/0x2b0
[  104.493461]  ? apic_timer_interrupt+0xa/0x20
[  104.495802]  __do_softirq+0x17c/0x627
[  104.497954]  irq_exit+0x114/0x140
[  104.499798]  smp_apic_timer_interrupt+0xde/0x380
[  104.502340]  apic_timer_interrupt+0xf/0x20
[  104.504607]  </IRQ>
======================================================
The following are links related to kernel 5.15:
Description: rcu: INFO: rcu_sched self-detected stall on CPU
Kernel version: hwe-5.15
Kernel config: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.15/.config
C reproducer: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.15/CReproducerRcu.c
Crash log: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.15/CrashLog.txt
Syz repro: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.15/SyzReproRcu
Vm.log: https://github.com/LancyRiver/SoftLockup/blob/master/rcu_core_si/v5.15/vm_5dot15.log

Crash log:
[  115.490784] audit: type=1400 audit(1661428486.901:15): avc:  denied  { execmem } for  pid=281 comm="CReproducerRcu" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=process permissive=1
[  132.604057] hrtimer: interrupt took 13982 ns
[  136.826220] rcu: INFO: rcu_sched self-detected stall on CPU
[  136.828843] rcu: 	0-....: (1 GPs behind) idle=ef3/1/0x4000000000000000 softirq=2418/2419 fqs=5209 
[  136.832988] 	(t=21004 jiffies g=3289 q=201640)
[  136.835107] NMI backtrace for cpu 0
[  136.836798] CPU: 0 PID: 291 Comm: CReproducerRcu Not tainted 5.15.39 #1
[  136.839721] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[  136.843880] Call Trace:
[  136.845158]  <IRQ>
[  136.846144]  dump_stack_lvl+0x4d/0x66
[  136.848247]  nmi_cpu_backtrace.cold+0xd0/0xd5
[  136.850270]  ? _raw_write_lock_irqsave+0xd0/0xd0
[  136.852437]  ? lapic_can_unplug_cpu+0x70/0x70
[  136.854520]  nmi_trigger_cpumask_backtrace+0x15a/0x1b0
[  136.856961]  rcu_dump_cpu_stacks+0x1b8/0x202
[  136.858971]  rcu_sched_clock_irq.cold+0x1d2/0x417
[  136.860977]  ? hrtimer_run_queues+0x1d/0x310
[  136.863037]  update_process_times+0x11b/0x180
[  136.865024]  ? tick_sched_handle.isra.0+0x150/0x150
[  136.867320]  tick_sched_handle.isra.0+0x105/0x150
[  136.869365]  tick_sched_timer+0xca/0xf0
[  136.871140]  __hrtimer_run_queues+0x2e2/0x6a0
[  136.873114]  ? enqueue_hrtimer+0x1c0/0x1c0
[  136.874967]  ? kvm_clock_get_cycles+0xd/0x10
[  136.876857]  ? ktime_get_update_offsets_now+0x17f/0x240
[  136.879252]  hrtimer_interrupt+0x2c9/0x6c0
[  136.881099]  __sysvec_apic_timer_interrupt+0xc8/0x260
[  136.883367]  sysvec_apic_timer_interrupt+0x65/0x90
[  136.885456]  </IRQ>
[  136.886389]  <TASK>
[  136.887369]  asm_sysvec_apic_timer_interrupt+0x12/0x20
[  136.889669] RIP: 0010:task_function_call+0xf8/0x140
[  136.891991] Code: 44 8b 64 24 38 e8 e8 bd f3 ff 41 83 fc f5 74 b0 e8 dd bd f3 ff 48 b8 00 00 00 00 00 fc ff df 49 01 c5 41 c7 45 00 00 00 00 00 <41> c7 45 08 00 00 00 00 48 8b 44 24 78 65 48 33 04 25 28 00 00 00
[  136.900280] RSP: 0018:ffff888006cd7c30 EFLAGS: 00000282
[  136.902629] RAX: dffffc0000000000 RBX: ffff888005bbba00 RCX: ffffffffac847503
[  136.905834] RDX: ffff888005bbba00 RSI: 0000000000000000 RDI: ffff88800372b008
[  136.908889] RBP: ffffed1000b77749 R08: ffffffffb0c86018 R09: ffffffffb0c8600f
[  136.932729] R10: ffffffffb0c86017 R11: ffffffffb0c8601b R12: 0000000000000000
[  136.936527] R13: ffffed1000d9af86 R14: ffff888005bbba48 R15: dffffc0000000000
[  136.940063]  ? task_function_call+0xe3/0x140
[  136.942475]  ? perf_event_addr_filters_exec+0x300/0x300
[  136.944767]  ? ctx_resched+0x220/0x220
[  136.946522]  ? exclusive_event_installable+0x1a1/0x220
[  136.948839]  perf_install_in_context+0x25f/0x540
[  136.951008]  ? perf_group_attach+0x380/0x380
[  136.952979]  ? mutex_lock+0x89/0xd0
[  136.954676]  ? __mutex_lock_slowpath+0x10/0x10
[  136.956706]  ? exclusive_event_installable+0x1a1/0x220
[  136.959052]  __do_sys_perf_event_open+0x15ba/0x2340
[  136.961345]  ? perf_remove_from_context+0x1a0/0x1a0
[  136.963591]  ? kasan_unpoison+0x23/0x50
[  136.965394]  ? fpregs_assert_state_consistent+0x74/0xb0
[  136.967753]  ? exit_to_user_mode_prepare+0x2f/0x150
[  136.969969]  do_syscall_64+0x3b/0x90
[  136.971778]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[  136.974181] RIP: 0033:0x7f2fcb723469
[  136.977080] Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ff 49 2b 00 f7 d8 64 89 01 48
[  136.985256] RSP: 002b:00007ffeb8cd4c88 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
[  136.988673] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2fcb723469
[  136.991908] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000080
[  136.995134] RBP: 00007ffeb8cd4ca0 R08: 0000000000000000 R09: 00007ffeb8cd4ca0
[  136.998343] R10: 00000000ffffffff R11: 0000000000000246 R12: 000056542ba00ce0
[  137.001573] R13: 00007ffeb8cd4dc0 R14: 0000000000000000 R15: 0000000000000000
[  137.004773]  </TASK>
======================================================

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Ubuntulinux-hwe-5.13 package

BUG:soft lockup - CPU#0 stuck for 36s! rcu_core_si kernel/rcu/tree.c:2807

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linux-hwe-5.13 package