bisecting fixing commit since 1e986fe9ad15b8406034c504afc5ae76f0a8e852 building syzkaller on 3c7fef3361a6007112b26adc1c5a550189ef43fe testing commit 1e986fe9ad15b8406034c504afc5ae76f0a8e852 with gcc (GCC) 8.4.1 20210217 kernel signature: 6a354d2dd8fe3f607b541428fc5f577f1e459a8c678adf6ff1ab4ba91b3bcc03 run #0: crashed: KASAN: use-after-free Write in ext4_put_super run #1: crashed: KASAN: use-after-free Write in ext4_put_super run #2: crashed: KASAN: use-after-free Write in ext4_put_super run #3: crashed: KASAN: use-after-free Write in ext4_put_super run #4: crashed: KASAN: use-after-free Write in ext4_put_super run #5: crashed: KASAN: use-after-free Write in ext4_put_super run #6: crashed: KASAN: use-after-free Write in ext4_put_super run #7: crashed: KASAN: use-after-free Write in ext4_put_super run #8: crashed: KASAN: use-after-free Write in ext4_put_super run #9: crashed: KASAN: use-after-free Write in ext4_put_super run #10: crashed: KASAN: use-after-free Write in ext4_put_super run #11: crashed: KASAN: use-after-free Write in ext4_put_super run #12: crashed: KASAN: use-after-free Write in ext4_put_super run #13: crashed: KASAN: use-after-free Write in ext4_put_super run #14: crashed: KASAN: use-after-free Write in ext4_put_super run #15: crashed: KASAN: use-after-free Write in ext4_put_super run #16: crashed: KASAN: use-after-free Write in ext4_put_super run #17: crashed: KASAN: use-after-free Write in ext4_put_super run #18: crashed: KASAN: use-after-free Write in ext4_put_super run #19: crashed: INFO: task hung in ext4_put_super testing current HEAD eb575cd5d7f60241d016fdd13a9e86d962093c9b testing commit eb575cd5d7f60241d016fdd13a9e86d962093c9b with gcc (GCC) 8.4.1 20210217 kernel signature: 6930dbbc7222cf0d03eda3ce3e70608d1aac5a386619c773e1a3dbf6c52e7cf8 run #0: crashed: KASAN: use-after-free Write in ext4_put_super run #1: crashed: KASAN: use-after-free Write in ext4_put_super run #2: crashed: KASAN: use-after-free Write in ext4_put_super run #3: crashed: KASAN: use-after-free Write in ext4_put_super run #4: crashed: KASAN: use-after-free Write in ext4_put_super run #5: crashed: KASAN: use-after-free Write in ext4_put_super run #6: crashed: KASAN: use-after-free Write in ext4_put_super run #7: crashed: KASAN: use-after-free Write in ext4_put_super run #8: crashed: INFO: task hung in ext4_put_super run #9: crashed: INFO: task hung in ext4_put_super revisions tested: 2, total time: 30m19.838160355s (build: 15m59.827357432s, test: 13m59.883903016s) the crash still happens on HEAD commit msg: Linux 4.19.195 crash: INFO: task hung in ext4_put_super Bluetooth: hci3: command 0x0406 tx timeout ieee802154 phy0 wpan0: encryption failed: -22 ieee802154 phy1 wpan1: encryption failed: -22 ieee802154 phy0 wpan0: encryption failed: -22 ieee802154 phy1 wpan1: encryption failed: -22 INFO: task syz-executor.5:8477 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D23768 8477 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136 kthread_stop+0xc9/0x4c0 kernel/kthread.c:588 ext4_put_super+0x78a/0xd80 fs/ext4/super.c:1054 generic_shutdown_super+0x12d/0x330 fs/super.c:456 kill_block_super+0x96/0xe0 fs/super.c:1185 deactivate_locked_super+0x77/0xd0 fs/super.c:329 deactivate_super fs/super.c:360 [inline] deactivate_super+0x13f/0x160 fs/super.c:356 cleanup_mnt+0xa3/0x130 fs/namespace.c:1098 __cleanup_mnt+0xd/0x10 fs/namespace.c:1105 task_work_run+0x108/0x180 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x185/0x1e0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x467a37 Code: Bad RIP value. RSP: 002b:00007ffc1f8b2ab8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000467a37 RDX: 00007ffc1f8b2b8b RSI: 0000000000000002 RDI: 00007ffc1f8b2b80 RBP: 00007ffc1f8b2b80 R08: 00000000ffffffff R09: 00007ffc1f8b2950 R10: 0000000002c9b8e3 R11: 0000000000000246 R12: 00000000004bee70 R13: 00007ffc1f8b3c50 R14: 0000000002c9b810 R15: 00007ffc1f8b3c90 Showing all locks held in the system: 1 lock held by khungtaskd/1570: #0: 000000008da26f05 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 1 lock held by syz-executor.5/8477: #0: 000000008486f98e (&type->s_umount_key#36){++++}, at: deactivate_super fs/super.c:359 [inline] #0: 000000008486f98e (&type->s_umount_key#36){++++}, at: deactivate_super+0x137/0x160 fs/super.c:356 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1570 Comm: khungtaskd Not tainted 4.19.195-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+0x17c/0x226 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf6/0x120 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline] watchdog+0x5c3/0xb40 kernel/hung_task.c:287 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60