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* KASAN: stack-out-of-bounds Read in timerqueue_add (2)
@ 2019-01-04 16:37 syzbot
  2019-01-04 16:39 ` Dmitry Vyukov
  0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2019-01-04 16:37 UTC (permalink / raw)
  To: linux-kernel, syzkaller-bugs, tglx

Hello,

syzbot found the following crash on:

HEAD commit:    6a1d293238c1 Add linux-next specific files for 20181224
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17c483fd400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=af046212050aa3ac
dashboard link: https://syzkaller.appspot.com/bug?extid=e9d7ff8272314cfce80d
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11b21480c00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1345f5bf400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e9d7ff8272314cfce80d@syzkaller.appspotmail.com

==================================================================
kasan: CONFIG_KASAN_INLINE enabled
BUG: KASAN: stack-out-of-bounds in timerqueue_add+0x2a5/0x320  
lib/timerqueue.c:52
kasan: GPF could be caused by NULL-ptr deref or user memory access
Read of size 8 at addr ffff8880a941f478 by task syz-executor881/7978
general protection fault: 0000 [#1] PREEMPT SMP KASAN

CPU: 1 PID: 3 Comm:  Not tainted 4.20.0-rc7-next-20181224 #1
CPU: 0 PID: 7978 Comm: syz-executor881 Not tainted 4.20.0-rc7-next-20181224  
#1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:191 [inline]
RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:85 [inline]
RIP: 0010:account_group_system_time include/linux/sched/cputime.h:149  
[inline]
RIP: 0010:account_system_index_time+0xe8/0x5f0 kernel/sched/cputime.c:168
Call Trace:
Code: 04 00 00 49 8b 84 24 00 07 00 00 48 ba 00 00 00 00 00 fc ff df 48 8d  
b8 40 01 00 00 48 8d 88 28 01 00 00 48 89 fe 48 c1 ee 03 <0f> b6 14 16 48  
89 fe 83 e6 07 40 38 f2 7f 08 84 d2 0f 85 93 03 00
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
RSP: 0018:ffff8880ae707a80 EFLAGS: 00010006
RAX: 0000000041b58ab3 RBX: 1ffff11015ce0f54 RCX: 0000000041b58bdb
RDX: dffffc0000000000 RSI: 000000000836b17e RDI: 0000000041b58bf3
RBP: ffff8880ae707b48 R08: ffff8880ae71f5f0 R09: fffffbfff1335b3d
R10: fffffbfff1301b45 R11: ffffffff899ad9e3 R12: ffff8880a94c4440
  print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
R13: 000000000077a391 R14: 0000000000000003 R15: ffff8880ae707b20
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
CR2: 00000000006d7090 CR3: 0000000096f60000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
Call Trace:
  timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
  <IRQ>
  enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
  __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
  hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
  irqtime_account_process_tick.isra.0+0x3a2/0x490 kernel/sched/cputime.c:380
  account_process_tick+0x27f/0x350 kernel/sched/cputime.c:483
  update_process_times+0x25/0x80 kernel/time/timer.c:1633
  tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:161
  hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
  do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
  tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1271
  __run_hrtimer kernel/time/hrtimer.c:1389 [inline]
  __hrtimer_run_queues+0x3a7/0x1050 kernel/time/hrtimer.c:1451
  hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
  hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1509
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
  smp_apic_timer_interrupt+0x18d/0x760 arch/x86/kernel/apic/apic.c:1060
  __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
  __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
  __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
  </IRQ>
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
Modules linked in:
RIP: 0033:0x443ae0

======================================================
WARNING: possible circular locking dependency detected
4.20.0-rc7-next-20181224 #1 Not tainted
------------------------------------------------------
syz-executor881/7978 is trying to acquire lock:
000000007874c6ae ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70  
kernel/locking/semaphore.c:136

but task is already holding lock:
000000001e99e9d7 (report_lock){....}, at: start_report mm/kasan/report.c:85  
[inline]
000000001e99e9d7 (report_lock){....}, at: kasan_report+0xb1/0x15e  
mm/kasan/report.c:309

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (report_lock){....}:
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
        start_report mm/kasan/report.c:85 [inline]
        kasan_report+0xb1/0x15e mm/kasan/report.c:309
        __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
        timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
        enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
        __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
        hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
        hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
        do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
        hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
        __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
        __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
        __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
        do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #4 (hrtimer_bases.lock){-.-.}:
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
        lock_hrtimer_base.isra.0+0x75/0x130 kernel/time/hrtimer.c:165
        hrtimer_start_range_ns+0x120/0xda0 kernel/time/hrtimer.c:1104
        hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
        start_rt_bandwidth kernel/sched/rt.c:70 [inline]
        inc_rt_group kernel/sched/rt.c:1147 [inline]
        inc_rt_tasks kernel/sched/rt.c:1191 [inline]
        __enqueue_rt_entity kernel/sched/rt.c:1261 [inline]
        enqueue_rt_entity kernel/sched/rt.c:1305 [inline]
        enqueue_task_rt+0x95b/0x1010 kernel/sched/rt.c:1335
        enqueue_task+0xb9/0x380 kernel/sched/core.c:730
        __sched_setscheduler+0xe32/0x1fe0 kernel/sched/core.c:4336
        _sched_setscheduler+0x218/0x340 kernel/sched/core.c:4373
        sched_setscheduler+0xe/0x10 kernel/sched/core.c:4388
        watchdog_dev_init+0x109/0x1db drivers/watchdog/watchdog_dev.c:1144
        watchdog_init+0x81/0x294 drivers/watchdog/watchdog_core.c:355
        do_one_initcall+0x129/0x937 init/main.c:888
        do_initcall_level init/main.c:956 [inline]
        do_initcalls init/main.c:964 [inline]
        do_basic_setup init/main.c:982 [inline]
        kernel_init_freeable+0x4db/0x5ca init/main.c:1135
        kernel_init+0x12/0x1c5 init/main.c:1055
        ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

-> #3 (&rt_b->rt_runtime_lock){-.-.}:
        __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
        _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
        __enable_runtime kernel/sched/rt.c:786 [inline]
        rq_online_rt+0xb4/0x390 kernel/sched/rt.c:2178
        set_rq_online.part.0+0xe7/0x140 kernel/sched/core.c:5666
        set_rq_online kernel/sched/core.c:5772 [inline]
        sched_cpu_activate+0x29e/0x430 kernel/sched/core.c:5765
        cpuhp_invoke_callback+0x2f6/0x2110 kernel/cpu.c:168
        cpuhp_thread_fun+0x496/0x8a0 kernel/cpu.c:685
        smpboot_thread_fn+0x6ab/0xa10 kernel/smpboot.c:164
        kthread+0x357/0x430 kernel/kthread.c:246
        ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

-> #2 (&rq->lock){-.-.}:
        __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
        _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
        rq_lock kernel/sched/sched.h:1149 [inline]
        task_fork_fair+0xb5/0x7a0 kernel/sched/fair.c:10083
        sched_fork+0x437/0xb90 kernel/sched/core.c:2359
        copy_process+0x1ff6/0x8720 kernel/fork.c:1887
        _do_fork+0x1a9/0x1170 kernel/fork.c:2216
        kernel_thread+0x34/0x40 kernel/fork.c:2275
        rest_init+0x28/0x37b init/main.c:408
        arch_call_rest_init+0xe/0x1b
        start_kernel+0x882/0x8bd init/main.c:740
        x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
        x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
        secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #1 (&p->pi_lock){-.-.}:
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
        try_to_wake_up+0xb9/0x1480 kernel/sched/core.c:1965
        wake_up_process+0x10/0x20 kernel/sched/core.c:2129
        __up.isra.0+0x1c0/0x2a0 kernel/locking/semaphore.c:262
        up+0x13e/0x1c0 kernel/locking/semaphore.c:187
        __up_console_sem+0xb7/0x1c0 kernel/printk/printk.c:236
        console_unlock+0x743/0x1040 kernel/printk/printk.c:2473
        vprintk_emit+0x370/0x960 kernel/printk/printk.c:1978
        vprintk_default+0x28/0x30 kernel/printk/printk.c:2005
        vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
        printk+0xba/0xed kernel/printk/printk.c:2038
        check_stack_usage kernel/exit.c:755 [inline]
        do_exit.cold+0x57/0x16a kernel/exit.c:916
        do_group_exit+0x177/0x430 kernel/exit.c:970
        __do_sys_exit_group kernel/exit.c:981 [inline]
        __se_sys_exit_group kernel/exit.c:979 [inline]
        __x64_sys_exit_group+0x44/0x50 kernel/exit.c:979
        do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 ((console_sem).lock){-.-.}:
        lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
        down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
        __down_trylock_console_sem+0xa8/0x210 kernel/printk/printk.c:219
        console_trylock+0x15/0xa0 kernel/printk/printk.c:2289
        console_trylock_spinning kernel/printk/printk.c:1709 [inline]
        vprintk_emit+0x351/0x960 kernel/printk/printk.c:1977
        vprintk_default+0x28/0x30 kernel/printk/printk.c:2005
        vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
        printk+0xba/0xed kernel/printk/printk.c:2038
        start_report mm/kasan/report.c:86 [inline]
        kasan_report+0xc1/0x15e mm/kasan/report.c:309
        __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
        timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
        enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
        __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
        hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
        hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
        do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
        hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
        __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
        __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
        __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
        do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
   (console_sem).lock --> hrtimer_bases.lock --> report_lock

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(report_lock);
                                lock(hrtimer_bases.lock);
                                lock(report_lock);
   lock((console_sem).lock);

  *** DEADLOCK ***

2 locks held by syz-executor881/7978:
  #0: 0000000053a4f5fc (hrtimer_bases.lock){-.-.}, at:  
lock_hrtimer_base.isra.0+0x75/0x130 kernel/time/hrtimer.c:165
  #1: 000000001e99e9d7 (report_lock){....}, at: start_report  
mm/kasan/report.c:85 [inline]
  #1: 000000001e99e9d7 (report_lock){....}, at: kasan_report+0xb1/0x15e  
mm/kasan/report.c:309

stack backtrace:
CPU: 0 PID: 7978 Comm: syz-executor881 Not tainted 4.20.0-rc7-next-20181224  
#1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
  print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224
  check_prev_add kernel/locking/lockdep.c:1866 [inline]
  check_prevs_add kernel/locking/lockdep.c:1979 [inline]
  validate_chain kernel/locking/lockdep.c:2350 [inline]
  __lock_acquire+0x2fed/0x4a10 kernel/locking/lockdep.c:3338
  lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
  down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
  __down_trylock_console_sem+0xa8/0x210 kernel/printk/printk.c:219
  console_trylock+0x15/0xa0 kernel/printk/printk.c:2289
  console_trylock_spinning kernel/printk/printk.c:1709 [inline]
  vprintk_emit+0x351/0x960 kernel/printk/printk.c:1977
  vprintk_default+0x28/0x30 kernel/printk/printk.c:2005
  vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
  printk+0xba/0xed kernel/printk/printk.c:2038
  start_report mm/kasan/report.c:86 [inline]
  kasan_report+0xc1/0x15e mm/kasan/report.c:309
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
  timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
  enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
  __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
  hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
  hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
  do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
  hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
  __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
  __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
  __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x443ae0
Code: c0 5b 5d c3 66 0f 1f 44 00 00 8b 04 24 48 83 c4 18 5b 5d c3 66 0f 1f  
44 00 00 83 3d 11 b5 29 00 00 75 14 b8 23 00 00 00 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 74 21 fc ff c3 48 83 ec 08 e8 4a 44 00 00
RSP: 002b:00007ffc84f7ff38 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 0000000000000978 RCX: 0000000000443ae0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffc84f7ff40
RBP: 0000000000000978 R08: 0000000000000001 R09: 0000000001e99940
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000976
R13: 0000000000127235 R14: 0000000000000000 R15: 0000000000000000
---[ end trace 45e69f5e272f25f9 ]---
Code: c0 5b 5d c3 66 0f 1f 44 00 00 8b 04 24 48 83 c4 18 5b 5d c3 66 0f 1f  
44 00 00 83 3d 11 b5 29 00 00 75 14 b8 23 00 00 00 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 74 21 fc ff c3 48 83 ec 08 e8 4a 44 00 00
RIP: 0010:__read_once_size include/linux/compiler.h:191 [inline]
RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:85 [inline]
RIP: 0010:account_group_system_time include/linux/sched/cputime.h:149  
[inline]
RIP: 0010:account_system_index_time+0xe8/0x5f0 kernel/sched/cputime.c:168
RSP: 002b:00007ffc84f7ff38 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
Code: 04 00 00 49 8b 84 24 00 07 00 00 48 ba 00 00 00 00 00 fc ff df 48 8d  
b8 40 01 00 00 48 8d 88 28 01 00 00 48 89 fe 48 c1 ee 03 <0f> b6 14 16 48  
89 fe 83 e6 07 40 38 f2 7f 08 84 d2 0f 85 93 03 00
RAX: ffffffffffffffda RBX: 0000000000000978 RCX: 0000000000443ae0
RSP: 0018:ffff8880ae707a80 EFLAGS: 00010006
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffc84f7ff40
RAX: 0000000041b58ab3 RBX: 1ffff11015ce0f54 RCX: 0000000041b58bdb
RBP: 0000000000000978 R08: 0000000000000001 R09: 0000000001e99940
RDX: dffffc0000000000 RSI: 000000000836b17e RDI: 0000000041b58bf3
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000976
RBP: ffff8880ae707b48 R08: ffff8880ae71f5f0 R09: fffffbfff1335b3d
R13: 0000000000127235 R14: 0000000000000000 R15: 0000000000000000
R10: fffffbfff1301b45 R11: ffffffff899ad9e3 R12: ffff8880a94c4440

R13: 000000000077a391 R14: 0000000000000003 R15: ffff8880ae707b20
The buggy address belongs to the page:
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
page:ffffea0002a507c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
flags: 0x1fffc0000000000()
CR2: 00000000006d7090 CR3: 0000000096f60000 CR4: 00000000001406e0
raw: 01fffc0000000000 ffffea0002a507c8 ffffea0002a507c8 0000000000000000
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
page dumped because: kasan: bad access detected


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: KASAN: stack-out-of-bounds Read in timerqueue_add (2)
  2019-01-04 16:37 KASAN: stack-out-of-bounds Read in timerqueue_add (2) syzbot
@ 2019-01-04 16:39 ` Dmitry Vyukov
  0 siblings, 0 replies; 2+ messages in thread
From: Dmitry Vyukov @ 2019-01-04 16:39 UTC (permalink / raw)
  To: syzbot; +Cc: LKML, syzkaller-bugs, Thomas Gleixner, Stefano Brivio

On Fri, Jan 4, 2019 at 5:37 PM syzbot
<syzbot+e9d7ff8272314cfce80d@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    6a1d293238c1 Add linux-next specific files for 20181224
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17c483fd400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=af046212050aa3ac
> dashboard link: https://syzkaller.appspot.com/bug?extid=e9d7ff8272314cfce80d
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11b21480c00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1345f5bf400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+e9d7ff8272314cfce80d@syzkaller.appspotmail.com

From the reproducer looks like another manifestation of the stack
overflow/corruption:

#syz dup: kernel panic: stack is corrupted in udp4_lib_lookup2

See https://groups.google.com/forum/#!msg/syzkaller-bugs/vr87kmG5qRI/31nOcuVsFgAJ



> ==================================================================
> kasan: CONFIG_KASAN_INLINE enabled
> BUG: KASAN: stack-out-of-bounds in timerqueue_add+0x2a5/0x320
> lib/timerqueue.c:52
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> Read of size 8 at addr ffff8880a941f478 by task syz-executor881/7978
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
>
> CPU: 1 PID: 3 Comm:  Not tainted 4.20.0-rc7-next-20181224 #1
> CPU: 0 PID: 7978 Comm: syz-executor881 Not tainted 4.20.0-rc7-next-20181224
> #1
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:__read_once_size include/linux/compiler.h:191 [inline]
> RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:85 [inline]
> RIP: 0010:account_group_system_time include/linux/sched/cputime.h:149
> [inline]
> RIP: 0010:account_system_index_time+0xe8/0x5f0 kernel/sched/cputime.c:168
> Call Trace:
> Code: 04 00 00 49 8b 84 24 00 07 00 00 48 ba 00 00 00 00 00 fc ff df 48 8d
> b8 40 01 00 00 48 8d 88 28 01 00 00 48 89 fe 48 c1 ee 03 <0f> b6 14 16 48
> 89 fe 83 e6 07 40 38 f2 7f 08 84 d2 0f 85 93 03 00
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
> RSP: 0018:ffff8880ae707a80 EFLAGS: 00010006
> RAX: 0000000041b58ab3 RBX: 1ffff11015ce0f54 RCX: 0000000041b58bdb
> RDX: dffffc0000000000 RSI: 000000000836b17e RDI: 0000000041b58bf3
> RBP: ffff8880ae707b48 R08: ffff8880ae71f5f0 R09: fffffbfff1335b3d
> R10: fffffbfff1301b45 R11: ffffffff899ad9e3 R12: ffff8880a94c4440
>   print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
> R13: 000000000077a391 R14: 0000000000000003 R15: ffff8880ae707b20
> FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
> CR2: 00000000006d7090 CR3: 0000000096f60000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
> Call Trace:
>   timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
>   <IRQ>
>   enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
>   __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
>   hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
>   irqtime_account_process_tick.isra.0+0x3a2/0x490 kernel/sched/cputime.c:380
>   account_process_tick+0x27f/0x350 kernel/sched/cputime.c:483
>   update_process_times+0x25/0x80 kernel/time/timer.c:1633
>   tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:161
>   hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
>   do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
>   tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1271
>   __run_hrtimer kernel/time/hrtimer.c:1389 [inline]
>   __hrtimer_run_queues+0x3a7/0x1050 kernel/time/hrtimer.c:1451
>   hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
>   hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1509
>   local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
>   smp_apic_timer_interrupt+0x18d/0x760 arch/x86/kernel/apic/apic.c:1060
>   __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
>   __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
>   __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
>   do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>   apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
>   </IRQ>
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> Modules linked in:
> RIP: 0033:0x443ae0
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 4.20.0-rc7-next-20181224 #1 Not tainted
> ------------------------------------------------------
> syz-executor881/7978 is trying to acquire lock:
> 000000007874c6ae ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70
> kernel/locking/semaphore.c:136
>
> but task is already holding lock:
> 000000001e99e9d7 (report_lock){....}, at: start_report mm/kasan/report.c:85
> [inline]
> 000000001e99e9d7 (report_lock){....}, at: kasan_report+0xb1/0x15e
> mm/kasan/report.c:309
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #5 (report_lock){....}:
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
>         start_report mm/kasan/report.c:85 [inline]
>         kasan_report+0xb1/0x15e mm/kasan/report.c:309
>         __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
>         timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
>         enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
>         __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
>         hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
>         hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
>         do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
>         hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
>         __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
>         __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
>         __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
>         do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> -> #4 (hrtimer_bases.lock){-.-.}:
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
>         lock_hrtimer_base.isra.0+0x75/0x130 kernel/time/hrtimer.c:165
>         hrtimer_start_range_ns+0x120/0xda0 kernel/time/hrtimer.c:1104
>         hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
>         start_rt_bandwidth kernel/sched/rt.c:70 [inline]
>         inc_rt_group kernel/sched/rt.c:1147 [inline]
>         inc_rt_tasks kernel/sched/rt.c:1191 [inline]
>         __enqueue_rt_entity kernel/sched/rt.c:1261 [inline]
>         enqueue_rt_entity kernel/sched/rt.c:1305 [inline]
>         enqueue_task_rt+0x95b/0x1010 kernel/sched/rt.c:1335
>         enqueue_task+0xb9/0x380 kernel/sched/core.c:730
>         __sched_setscheduler+0xe32/0x1fe0 kernel/sched/core.c:4336
>         _sched_setscheduler+0x218/0x340 kernel/sched/core.c:4373
>         sched_setscheduler+0xe/0x10 kernel/sched/core.c:4388
>         watchdog_dev_init+0x109/0x1db drivers/watchdog/watchdog_dev.c:1144
>         watchdog_init+0x81/0x294 drivers/watchdog/watchdog_core.c:355
>         do_one_initcall+0x129/0x937 init/main.c:888
>         do_initcall_level init/main.c:956 [inline]
>         do_initcalls init/main.c:964 [inline]
>         do_basic_setup init/main.c:982 [inline]
>         kernel_init_freeable+0x4db/0x5ca init/main.c:1135
>         kernel_init+0x12/0x1c5 init/main.c:1055
>         ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
>
> -> #3 (&rt_b->rt_runtime_lock){-.-.}:
>         __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>         _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
>         __enable_runtime kernel/sched/rt.c:786 [inline]
>         rq_online_rt+0xb4/0x390 kernel/sched/rt.c:2178
>         set_rq_online.part.0+0xe7/0x140 kernel/sched/core.c:5666
>         set_rq_online kernel/sched/core.c:5772 [inline]
>         sched_cpu_activate+0x29e/0x430 kernel/sched/core.c:5765
>         cpuhp_invoke_callback+0x2f6/0x2110 kernel/cpu.c:168
>         cpuhp_thread_fun+0x496/0x8a0 kernel/cpu.c:685
>         smpboot_thread_fn+0x6ab/0xa10 kernel/smpboot.c:164
>         kthread+0x357/0x430 kernel/kthread.c:246
>         ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
>
> -> #2 (&rq->lock){-.-.}:
>         __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>         _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
>         rq_lock kernel/sched/sched.h:1149 [inline]
>         task_fork_fair+0xb5/0x7a0 kernel/sched/fair.c:10083
>         sched_fork+0x437/0xb90 kernel/sched/core.c:2359
>         copy_process+0x1ff6/0x8720 kernel/fork.c:1887
>         _do_fork+0x1a9/0x1170 kernel/fork.c:2216
>         kernel_thread+0x34/0x40 kernel/fork.c:2275
>         rest_init+0x28/0x37b init/main.c:408
>         arch_call_rest_init+0xe/0x1b
>         start_kernel+0x882/0x8bd init/main.c:740
>         x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
>         x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
>         secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
>
> -> #1 (&p->pi_lock){-.-.}:
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
>         try_to_wake_up+0xb9/0x1480 kernel/sched/core.c:1965
>         wake_up_process+0x10/0x20 kernel/sched/core.c:2129
>         __up.isra.0+0x1c0/0x2a0 kernel/locking/semaphore.c:262
>         up+0x13e/0x1c0 kernel/locking/semaphore.c:187
>         __up_console_sem+0xb7/0x1c0 kernel/printk/printk.c:236
>         console_unlock+0x743/0x1040 kernel/printk/printk.c:2473
>         vprintk_emit+0x370/0x960 kernel/printk/printk.c:1978
>         vprintk_default+0x28/0x30 kernel/printk/printk.c:2005
>         vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
>         printk+0xba/0xed kernel/printk/printk.c:2038
>         check_stack_usage kernel/exit.c:755 [inline]
>         do_exit.cold+0x57/0x16a kernel/exit.c:916
>         do_group_exit+0x177/0x430 kernel/exit.c:970
>         __do_sys_exit_group kernel/exit.c:981 [inline]
>         __se_sys_exit_group kernel/exit.c:979 [inline]
>         __x64_sys_exit_group+0x44/0x50 kernel/exit.c:979
>         do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> -> #0 ((console_sem).lock){-.-.}:
>         lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
>         down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
>         __down_trylock_console_sem+0xa8/0x210 kernel/printk/printk.c:219
>         console_trylock+0x15/0xa0 kernel/printk/printk.c:2289
>         console_trylock_spinning kernel/printk/printk.c:1709 [inline]
>         vprintk_emit+0x351/0x960 kernel/printk/printk.c:1977
>         vprintk_default+0x28/0x30 kernel/printk/printk.c:2005
>         vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
>         printk+0xba/0xed kernel/printk/printk.c:2038
>         start_report mm/kasan/report.c:86 [inline]
>         kasan_report+0xc1/0x15e mm/kasan/report.c:309
>         __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
>         timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
>         enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
>         __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
>         hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
>         hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
>         do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
>         hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
>         __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
>         __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
>         __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
>         do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> other info that might help us debug this:
>
> Chain exists of:
>    (console_sem).lock --> hrtimer_bases.lock --> report_lock
>
>   Possible unsafe locking scenario:
>
>         CPU0                    CPU1
>         ----                    ----
>    lock(report_lock);
>                                 lock(hrtimer_bases.lock);
>                                 lock(report_lock);
>    lock((console_sem).lock);
>
>   *** DEADLOCK ***
>
> 2 locks held by syz-executor881/7978:
>   #0: 0000000053a4f5fc (hrtimer_bases.lock){-.-.}, at:
> lock_hrtimer_base.isra.0+0x75/0x130 kernel/time/hrtimer.c:165
>   #1: 000000001e99e9d7 (report_lock){....}, at: start_report
> mm/kasan/report.c:85 [inline]
>   #1: 000000001e99e9d7 (report_lock){....}, at: kasan_report+0xb1/0x15e
> mm/kasan/report.c:309
>
> stack backtrace:
> CPU: 0 PID: 7978 Comm: syz-executor881 Not tainted 4.20.0-rc7-next-20181224
> #1
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
>   print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224
>   check_prev_add kernel/locking/lockdep.c:1866 [inline]
>   check_prevs_add kernel/locking/lockdep.c:1979 [inline]
>   validate_chain kernel/locking/lockdep.c:2350 [inline]
>   __lock_acquire+0x2fed/0x4a10 kernel/locking/lockdep.c:3338
>   lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841
>   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>   _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
>   down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
>   __down_trylock_console_sem+0xa8/0x210 kernel/printk/printk.c:219
>   console_trylock+0x15/0xa0 kernel/printk/printk.c:2289
>   console_trylock_spinning kernel/printk/printk.c:1709 [inline]
>   vprintk_emit+0x351/0x960 kernel/printk/printk.c:1977
>   vprintk_default+0x28/0x30 kernel/printk/printk.c:2005
>   vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
>   printk+0xba/0xed kernel/printk/printk.c:2038
>   start_report mm/kasan/report.c:86 [inline]
>   kasan_report+0xc1/0x15e mm/kasan/report.c:309
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
>   timerqueue_add+0x2a5/0x320 lib/timerqueue.c:52
>   enqueue_hrtimer+0x1ae/0x570 kernel/time/hrtimer.c:951
>   __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
>   hrtimer_start_range_ns+0x62a/0xda0 kernel/time/hrtimer.c:1106
>   hrtimer_start_expires include/linux/hrtimer.h:409 [inline]
>   do_nanosleep+0x1a2/0x750 kernel/time/hrtimer.c:1676
>   hrtimer_nanosleep+0x2e4/0x640 kernel/time/hrtimer.c:1733
>   __do_sys_nanosleep kernel/time/hrtimer.c:1767 [inline]
>   __se_sys_nanosleep kernel/time/hrtimer.c:1754 [inline]
>   __x64_sys_nanosleep+0x1e0/0x280 kernel/time/hrtimer.c:1754
>   do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x443ae0
> Code: c0 5b 5d c3 66 0f 1f 44 00 00 8b 04 24 48 83 c4 18 5b 5d c3 66 0f 1f
> 44 00 00 83 3d 11 b5 29 00 00 75 14 b8 23 00 00 00 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 74 21 fc ff c3 48 83 ec 08 e8 4a 44 00 00
> RSP: 002b:00007ffc84f7ff38 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
> RAX: ffffffffffffffda RBX: 0000000000000978 RCX: 0000000000443ae0
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffc84f7ff40
> RBP: 0000000000000978 R08: 0000000000000001 R09: 0000000001e99940
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000976
> R13: 0000000000127235 R14: 0000000000000000 R15: 0000000000000000
> ---[ end trace 45e69f5e272f25f9 ]---
> Code: c0 5b 5d c3 66 0f 1f 44 00 00 8b 04 24 48 83 c4 18 5b 5d c3 66 0f 1f
> 44 00 00 83 3d 11 b5 29 00 00 75 14 b8 23 00 00 00 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 74 21 fc ff c3 48 83 ec 08 e8 4a 44 00 00
> RIP: 0010:__read_once_size include/linux/compiler.h:191 [inline]
> RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:85 [inline]
> RIP: 0010:account_group_system_time include/linux/sched/cputime.h:149
> [inline]
> RIP: 0010:account_system_index_time+0xe8/0x5f0 kernel/sched/cputime.c:168
> RSP: 002b:00007ffc84f7ff38 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
> Code: 04 00 00 49 8b 84 24 00 07 00 00 48 ba 00 00 00 00 00 fc ff df 48 8d
> b8 40 01 00 00 48 8d 88 28 01 00 00 48 89 fe 48 c1 ee 03 <0f> b6 14 16 48
> 89 fe 83 e6 07 40 38 f2 7f 08 84 d2 0f 85 93 03 00
> RAX: ffffffffffffffda RBX: 0000000000000978 RCX: 0000000000443ae0
> RSP: 0018:ffff8880ae707a80 EFLAGS: 00010006
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffc84f7ff40
> RAX: 0000000041b58ab3 RBX: 1ffff11015ce0f54 RCX: 0000000041b58bdb
> RBP: 0000000000000978 R08: 0000000000000001 R09: 0000000001e99940
> RDX: dffffc0000000000 RSI: 000000000836b17e RDI: 0000000041b58bf3
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000976
> RBP: ffff8880ae707b48 R08: ffff8880ae71f5f0 R09: fffffbfff1335b3d
> R13: 0000000000127235 R14: 0000000000000000 R15: 0000000000000000
> R10: fffffbfff1301b45 R11: ffffffff899ad9e3 R12: ffff8880a94c4440
>
> R13: 000000000077a391 R14: 0000000000000003 R15: ffff8880ae707b20
> The buggy address belongs to the page:
> FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
> page:ffffea0002a507c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> flags: 0x1fffc0000000000()
> CR2: 00000000006d7090 CR3: 0000000096f60000 CR4: 00000000001406e0
> raw: 01fffc0000000000 ffffea0002a507c8 ffffea0002a507c8 0000000000000000
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> page dumped because: kasan: bad access detected
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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2019-01-04 16:37 KASAN: stack-out-of-bounds Read in timerqueue_add (2) syzbot
2019-01-04 16:39 ` Dmitry Vyukov

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