Hello,

syzbot hit the following crash on upstream commit 3fd14cdcc05a682b03743683ce3a726898b20555 (Fri Apr 6 19:15:41 2018 +0000) Merge tag 'mtd/for-4.17' of git://git.infradead.org/linux-mtd syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=584505e6ccdbedcf7629

Unfortunately, I don't have any reproducer for this crash yet. Raw console output: https://syzkaller.appspot.com/x/log.txt?id=5653573555716096 Kernel config: https://syzkaller.appspot.com/x/.config?id=-5813481738265533882 compiler: gcc (GCC) 8.0.1 20180301 (experimental)

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random: crng init done INFO: rcu_sched self-detected stall on CPU 1-....: (124996 ticks this GP) idle=c9a/1/4611686018427387906 softirq=17918/17918 fqs=31239 (t=125000 jiffies g=9607 c=9606 q=187) NMI backtrace for cpu 1 CPU: 1 PID: 6608 Comm: syz-executor4 Not tainted 4.16.0+ #4 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+0x1b9/0x294 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline] rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1376 print_cpu_stall kernel/rcu/tree.c:1525 [inline] check_cpu_stall.isra.61.cold.80+0x36c/0x59a kernel/rcu/tree.c:1593 __rcu_pending kernel/rcu/tree.c:3356 [inline] rcu_pending kernel/rcu/tree.c:3401 [inline] rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763 update_process_times+0x2d/0x70 kernel/time/timer.c:1636 tick_sched_handle+0xa0/0x180 kernel/time/tick-sched.c:171 tick_sched_timer+0x42/0x130 kernel/time/tick-sched.c:1179 __run_hrtimer kernel/time/hrtimer.c:1337 [inline] __hrtimer_run_queues+0x3e3/0x10a0 kernel/time/hrtimer.c:1399 hrtimer_interrupt+0x286/0x650 kernel/time/hrtimer.c:1457 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] smp_apic_timer_interrupt+0x15d/0x710 arch/x86/kernel/apic/apic.c:1050 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:862 </IRQ> RIP: 0010:check_kcov_mode kernel/kcov.c:67 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x20/0x50 kernel/kcov.c:101 RSP: 0018:ffff8801c82feb50 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: ffff8801b5330040 RBX: 0000000000000000 RCX: 1ffff10036a6611b RDX: 0000000000000000 RSI: ffffffff859d514c RDI: ffffffff88b172b8 RBP: ffff8801c82feb50 R08: ffff8801b53308b8 R09: 0000000000000006 R10: ffff8801b5330040 R11: 0000000000000000 R12: 0000000000000004 R13: 00000000ffffffe0 R14: ffff8801d128ab00 R15: ffff8801ce80e040 snd_pcm_stream_unlock_irq+0xbc/0xf0 sound/core/pcm_native.c:167 __snd_pcm_lib_xfer+0x739/0x1d10 sound/core/pcm_lib.c:2246 snd_pcm_oss_write3+0xe9/0x220 sound/core/oss/pcm_oss.c:1236 snd_pcm_oss_write2+0x34c/0x460 sound/core/oss/pcm_oss.c:1373 snd_pcm_oss_sync1+0x332/0x5a0 sound/core/oss/pcm_oss.c:1606 snd_pcm_oss_sync.isra.29+0x790/0x980 sound/core/oss/pcm_oss.c:1682 snd_pcm_oss_release+0x214/0x290 sound/core/oss/pcm_oss.c:2559 __fput+0x34d/0x890 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x1e4/0x290 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x1aee/0x2730 kernel/exit.c:865 do_group_exit+0x16f/0x430 kernel/exit.c:968 get_signal+0x886/0x1960 kernel/signal.c:2469 do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810 exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:265 [inline] do_syscall_64+0x792/0x9d0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x455259 RSP: 002b:00007f20e223bce8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000072c038 RCX: 0000000000455259 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000072c038 RBP: 000000000072c038 R08: 0000000000000000 R09: 000000000072c010 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000a3e81f R14: 00007f20e223c9c0 R15: 0000000000000002

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