Message-ID: <000000000000d5b2330598c87921@google.com>
Date:   Tue, 03 Dec 2019 00:28:08 -0800
From:   syzbot <syzbot+6176df02eb1a01d00646@...kaller.appspotmail.com>
To:     aarcange@...hat.com, akpm@...ux-foundation.org,
        christian@...uner.io, christian@...lner.me, cyphar@...har.com,
        elena.reshetova@...el.com, jgg@...pe.ca, keescook@...omium.org,
        ldv@...linux.org, linux-kernel@...r.kernel.org,
        luto@...capital.net, mingo@...nel.org, peterz@...radead.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        viro@...iv.linux.org.uk, wad@...omium.org
Subject: INFO: rcu detected stall in security_file_free

Hello,

syzbot found the following crash on:

HEAD commit:    596cf45c Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1327942ae00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9bbcda576154a4b4
dashboard link: https://syzkaller.appspot.com/bug?extid=6176df02eb1a01d00646
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6176df02eb1a01d00646@...kaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10499 ticks this GP) idle=f6a/1/0x4000000000000002  
softirq=9928/9928 fqs=38
	(t=10501 jiffies g=6205 q=398)
rcu: rcu_preempt kthread starved for 10424 jiffies! g6205 f0x0  
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29032    10      2 0x80004000
Call Trace:
  context_switch kernel/sched/core.c:3385 [inline]
  __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
  schedule+0x181/0x210 kernel/sched/core.c:4155
  schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
  rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
  rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
  kthread+0x332/0x350 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 0
CPU: 0 PID: 8045 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1fb/0x318 lib/dump_stack.c:118
  nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
  nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62
  arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
  trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
  rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254
  print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
  check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
  rcu_pending kernel/rcu/tree.c:2827 [inline]
  rcu_sched_clock_irq+0xe25/0x1ad0 kernel/rcu/tree.c:2271
  update_process_times+0x12d/0x180 kernel/time/timer.c:1726
  tick_sched_handle kernel/time/tick-sched.c:167 [inline]
  tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
  __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
  __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1576
  hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1638
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
  smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
  </IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:98
Code: 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 53 48 89 fb e8 13 00 00 00  
48 8b 3d 34 e7 cc 07 48 89 de e8 64 02 3b 00 5b 5d c3 cc <48> 8b 04 24 65  
48 8b 0c 25 c0 1d 02 00 65 8b 15 b8 81 8b 7e f7 c2
RSP: 0018:ffffc90001f87a90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11013f36931 RBX: ffffea00029e3f40 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea00029e3f40
RBP: ffffc90001f87ab8 R08: dffffc0000000000 R09: fffffbfff120248a
R10: fffffbfff120248a R11: 0000000000000000 R12: ffff88809f9b4a20
R13: dffffc0000000000 R14: 00000000fffffffc R15: ffff8880a8747628
  free_thread_stack+0x168/0x590 kernel/fork.c:280
  release_task_stack kernel/fork.c:440 [inline]
  put_task_stack+0xa3/0x130 kernel/fork.c:451
  finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
  context_switch kernel/sched/core.c:3388 [inline]
  __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
  preempt_schedule_irq+0xc1/0x140 kernel/sched/core.c:4338
  retint_kernel+0x1b/0x2b
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752  
[inline]
RIP: 0010:kmem_cache_free+0xc8/0xf0 mm/slab.c:3695
Code: 58 07 00 74 42 4c 89 f7 57 9d 0f 1f 44 00 00 e8 0e 98 ca ff eb 19 e8  
a7 95 ca ff 48 83 3d 07 f7 58 07 00 74 24 4c 89 f7 57 9d <0f> 1f 44 00 00  
4c 89 e7 4c 89 fe e8 58 01 00 00 5b 41 5c 41 5e 41
RSP: 0018:ffffc90001f87d10 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: ffff88809753ced4 RBX: ffff8880aa9eb000 RCX: ffff88809753c640
RDX: 0000000000000000 RSI: ffffffff83474bc4 RDI: 0000000000000286
RBP: ffffc90001f87d30 R08: ffff88809753ce98 R09: ffffc90001f87b14
R10: 000000000000000b R11: 0000000000000000 R12: ffffffff83474bc4
R13: ffff888095bf2cc0 R14: 0000000000000286 R15: ffff8880a304d1f8
  security_file_free+0xc4/0xe0 security/security.c:1403
  file_free fs/file_table.c:55 [inline]
  __fput+0x506/0x740 fs/file_table.c:298
  ____fput+0x15/0x20 fs/file_table.c:313
  task_work_run+0x17e/0x1b0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop arch/x86/entry/common.c:164 [inline]
  prepare_exit_to_usermode+0x483/0x5b0 arch/x86/entry/common.c:195
  syscall_return_slowpath+0x113/0x4a0 arch/x86/entry/common.c:278
  do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:304
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45e433
Code: 48 89 ee 48 89 e7 e8 2c 1f fa ff 31 c0 48 89 e2 be 33 89 00 00 89 df  
e8 bb c0 ff ff 85 c0 78 17 48 63 fb b8 03 00 00 00 0f 05 <8b> 44 24 10 48  
83 c4 38 5b 5d c3 66 90 48 c7 c2 d4 ff ff ff 48 63
RSP: 002b:00007ffe95171aa0 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 000000000045e433
RDX: 00007ffe95171aa0 RSI: 0000000000008933 RDI: 0000000000000004
RBP: 00000000004bfb19 R08: 000000000000000a R09: 000000000000000a
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000006 R14: 0000000000000000 R15: 00007ffe95171d30


---
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