bisecting fixing commit since fb0155a09b0224a7147cb07a4ce6034c8d29667f building syzkaller on 1b88c6d5c8477f1d4fb3b389443b200acc32e9a8 testing commit fb0155a09b0224a7147cb07a4ce6034c8d29667f with gcc (GCC) 8.1.0 kernel signature: 11c2edb6d0b21ae177e544419404d48ed572eea722b27fb78dddce8c493939d6 all runs: crashed: INFO: task hung in nbd_ioctl testing current HEAD 23859ae44402f4d935b9ee548135dd1e65e2cbf4 testing commit 23859ae44402f4d935b9ee548135dd1e65e2cbf4 with gcc (GCC) 8.1.0 kernel signature: 5bba86629ab24fa82a189b0bc240a2bcf78783977f178115627dd09650c434d9 all runs: crashed: INFO: task hung in nbd_ioctl revisions tested: 2, total time: 22m35.139135805s (build: 10m33.081718968s, test: 11m23.961850794s) the crash still happens on HEAD commit msg: Merge tag 'trace-v5.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace crash: INFO: task hung in nbd_ioctl INFO: task syz-executor.3:11679 blocked for more than 143 seconds. Not tainted 5.10.0-rc1-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.3 state:D stack:14424 pid:11679 ppid: 6996 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:3774 [inline] __schedule+0x418/0x900 kernel/sched/core.c:4523 schedule+0x38/0xe0 kernel/sched/core.c:4601 schedule_timeout+0x275/0x360 kernel/time/timer.c:1852 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion+0xa7/0x110 kernel/sched/completion.c:138 flush_workqueue+0x1ca/0x590 kernel/workqueue.c:2835 nbd_start_device_ioctl drivers/block/nbd.c:1331 [inline] __nbd_ioctl drivers/block/nbd.c:1408 [inline] nbd_ioctl+0x262/0x3a0 drivers/block/nbd.c:1448 __blkdev_driver_ioctl block/ioctl.c:228 [inline] blkdev_ioctl+0x1d1/0x2b0 block/ioctl.c:623 block_ioctl+0x3a/0x40 fs/block_dev.c:1869 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x7c/0xb0 fs/ioctl.c:739 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45dd99 Code: Unable to access opcode bytes at RIP 0x45dd6f. RSP: 002b:00007f3a337b5c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000012e80 RCX: 000000000045dd99 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003 RBP: 000000000118c000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bfd4 R13: 00007fff8a505fff R14: 00007f3a337b69c0 R15: 000000000118bfd4 Showing all locks held in the system: 1 lock held by khungtaskd/1181: #0: ffffffff847fbd40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x15/0x17a kernel/locking/lockdep.c:6260 2 locks held by kworker/u5:0/1557: #0: ffff88811ebc2938 ((wq_completion)knbd3-recv){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff88811ebc2938 ((wq_completion)knbd3-recv){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff88811ebc2938 ((wq_completion)knbd3-recv){+.+.}-{0:0}, at: process_one_work+0x1e6/0x600 kernel/workqueue.c:2243 #1: ffffc90003687e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #1: ffffc90003687e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #1: ffffc90003687e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x1e6/0x600 kernel/workqueue.c:2243 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1181 Comm: khungtaskd Not tainted 5.10.0-rc1-syzkaller #0 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+0xa3/0xc8 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.8+0x53/0x6d lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace+0xd5/0xf0 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline] watchdog+0x57f/0x670 kernel/hung_task.c:295 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 7 Comm: kworker/u4:0 Not tainted 5.10.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:__this_cpu_preempt_check+0x0/0x10 lib/smp_processor_id.c:64 Code: 51 ff ff ff 0f 0b 0f 1f 40 00 48 c7 c6 c6 fd 29 84 48 c7 c7 55 7b 0d 84 e9 1d ff ff ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 <48> 89 fe 48 c7 c7 ee 4c 19 84 e9 01 ff ff ff cc eb 1e 0f 1f 00 48 RSP: 0018:ffffc90000ca3d00 EFLAGS: 00000046 RAX: 0000000000000000 RBX: ffff888100c52af8 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffffffff847fbcc0 RDI: ffffffff8409fd9f RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: ffff888100c521c0 R13: ffff888100c52ad0 R14: 00000000ffffffff R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2eecef77c0 CR3: 0000000104502000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: lockdep_recursion_finish kernel/locking/lockdep.c:435 [inline] lock_is_held_type+0xfb/0x160 kernel/locking/lockdep.c:5482 lock_is_held include/linux/lockdep.h:271 [inline] rcu_read_lock_sched_held+0x4d/0x80 kernel/rcu/update.c:123 trace_lock_acquire include/trace/events/lock.h:13 [inline] lock_acquire+0x2f2/0x420 kernel/locking/lockdep.c:5413 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:175 spin_lock_bh include/linux/spinlock.h:359 [inline] batadv_nc_purge_paths+0x43/0x110 net/batman-adv/network-coding.c:441 batadv_nc_worker+0x114/0x240 net/batman-adv/network-coding.c:721 process_one_work+0x273/0x600 kernel/workqueue.c:2272 worker_thread+0x38/0x380 kernel/workqueue.c:2418 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296