bisecting fixing commit since 78d697fc93f98054e36a3ab76dca1a88802ba7be building syzkaller on c88c7b75a4e022b758f4b0f1bf3db8ebb2fb25e6 testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0 kernel signature: e6f28d20b2518026a6048935dea1ef4b591aa4f7bd778c071eaf85dbab6c370c run #0: crashed: INFO: task hung in lo_open run #1: crashed: INFO: task hung in lo_open run #2: crashed: INFO: task hung in lo_release run #3: crashed: INFO: task hung in __blkdev_get run #4: crashed: INFO: task hung in lo_open run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing current HEAD 01364dad1d4577e27a57729d41053f661bb8a5b9 testing commit 01364dad1d4577e27a57729d41053f661bb8a5b9 with gcc (GCC) 8.1.0 kernel signature: 4be30b6e8c0e43372f5fd5ee1f9dceebc25660c2043133e6e7d688b352ea4c2a run #0: crashed: INFO: task hung in lo_open run #1: crashed: INFO: task hung in lo_open run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 39m35.695591353s (build: 16m57.487075808s, test: 22m1.334032034s) the crash still happens on HEAD commit msg: Linux 4.14.174 crash: INFO: task hung in lo_open NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 INFO: task syz-executor.4:6486 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D24888 6486 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_open+0x16/0xa0 drivers/block/loop.c:1634 __blkdev_get+0x2a4/0x1030 fs/block_dev.c:1472 blkdev_get+0x26d/0x860 fs/block_dev.c:1612 blkdev_open+0x19f/0x200 fs/block_dev.c:1770 do_dentry_open+0x620/0xdb0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xdde/0x3bd0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_open fs/open.c:1099 [inline] SyS_open+0x19/0x20 fs/open.c:1094 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4161f0 RSP: 002b:00007ffe8c212e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004161f0 RDX: 00007ffe8c212eea RSI: 0000000000000002 RDI: 00007ffe8c212ee0 RBP: 000000000071b460 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe8c212e90 R14: 0000000000000003 R15: 00007ffe8c212ea0 INFO: task syz-executor.5:6487 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D24504 6487 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_open+0x16/0xa0 drivers/block/loop.c:1634 __blkdev_get+0x2a4/0x1030 fs/block_dev.c:1472 blkdev_get+0x26d/0x860 fs/block_dev.c:1612 blkdev_open+0x19f/0x200 fs/block_dev.c:1770 do_dentry_open+0x620/0xdb0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xdde/0x3bd0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_open fs/open.c:1099 [inline] SyS_open+0x19/0x20 fs/open.c:1094 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4161f0 RSP: 002b:00007ffc2bee7c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004161f0 RDX: 00007ffc2bee7cfa RSI: 0000000000000002 RDI: 00007ffc2bee7cf0 RBP: 000000000071b460 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc2bee7ca0 R14: 0000000000000003 R15: 00007ffc2bee7cb0 INFO: task syz-executor.3:6488 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D24504 6488 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_open+0x16/0xa0 drivers/block/loop.c:1634 __blkdev_get+0x2a4/0x1030 fs/block_dev.c:1472 blkdev_get+0x26d/0x860 fs/block_dev.c:1612 blkdev_open+0x19f/0x200 fs/block_dev.c:1770 do_dentry_open+0x620/0xdb0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xdde/0x3bd0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_open fs/open.c:1099 [inline] SyS_open+0x19/0x20 fs/open.c:1094 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4161f0 RSP: 002b:00007ffd37d7f418 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004161f0 RDX: 00007ffd37d7f4aa RSI: 0000000000000002 RDI: 00007ffd37d7f4a0 RBP: 000000000071b460 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd37d7f450 R14: 0000000000000003 R15: 00007ffd37d7f460 INFO: task systemd-udevd:7774 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. systemd-udevd D27816 7774 3631 0x00000104 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_release+0x1a/0x180 drivers/block/loop.c:1677 __blkdev_put+0x406/0x730 fs/block_dev.c:1791 blkdev_put+0x73/0x480 fs/block_dev.c:1856 blkdev_close+0x88/0xd0 fs/block_dev.c:1863 __fput+0x232/0x750 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x16a/0x1b0 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x7f190c215270 RSP: 002b:00007ffc440b8ba8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f190c215270 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000007 RBP: 00007f190d0ce710 R08: 0000557016972b00 R09: 0000557016972800 R10: 00007f190d0ce8c0 R11: 0000000000000246 R12: 0000000000000000 R13: 0000557016972d10 R14: 0000000000000003 R15: 000000000000000e INFO: task syz-executor.2:7811 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D27936 7811 6478 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 blkdev_reread_part+0x18/0x40 block/ioctl.c:192 loop_reread_partitions+0x5d/0x70 drivers/block/loop.c:624 loop_set_status+0xb04/0x1070 drivers/block/loop.c:1193 loop_set_status64+0x83/0xc0 drivers/block/loop.c:1311 lo_ioctl+0x547/0x1c70 drivers/block/loop.c:1441 __blkdev_driver_ioctl block/ioctl.c:297 [inline] blkdev_ioctl+0x784/0x16b0 block/ioctl.c:594 block_ioctl+0xd7/0x130 fs/block_dev.c:1881 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c2e7 RSP: 002b:00007fbab31239d8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045c2e7 RDX: 00007fbab3123ac0 RSI: 0000000000004c04 RDI: 0000000000000004 RBP: 000000000076bf20 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000202 R12: 00000000ffffffff R13: 0000000000000c1c R14: 00000000004c138b R15: 000000000076bf2c INFO: task syz-executor.2:7815 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D29232 7815 6478 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 loop_control_ioctl+0xf6/0x2b0 drivers/block/loop.c:2007 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c479 RSP: 002b:00007fbab3102c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fbab31036d4 RCX: 000000000045c479 RDX: 9999999999999999 RSI: 0000000000004c81 RDI: 0000000000000006 RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000006b5 R14: 00000000004c9318 R15: 000000000076bfcc INFO: task syz-executor.2:7851 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28936 7851 6478 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 __blkdev_get+0x133/0x1030 fs/block_dev.c:1457 blkdev_get+0x26d/0x860 fs/block_dev.c:1612 blkdev_open+0x19f/0x200 fs/block_dev.c:1770 do_dentry_open+0x620/0xdb0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xdde/0x3bd0 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1081 SYSC_open fs/open.c:1099 [inline] SyS_open+0x19/0x20 fs/open.c:1094 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x416211 RSP: 002b:00007fbab30e19d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 00007fbab30e26d4 RCX: 0000000000416211 RDX: 00007fbab30e1bba RSI: 0000000000000002 RDI: 00007fbab30e1bb0 RBP: 000000000076c060 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000293 R12: 00000000ffffffff R13: 0000000000000c1c R14: 00000000004c138b R15: 000000000076c06c INFO: task syz-executor.2:7854 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D29608 7854 6478 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c479 RSP: 002b:00007fbab30c0c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fbab30c16d4 RCX: 000000000045c479 RDX: 9999999999999999 RSI: 0000000000004c81 RDI: 0000000000000006 RBP: 000000000076c100 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000006b5 R14: 00000000004c9318 R15: 000000000076c10c INFO: task syz-executor.0:7824 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28776 7824 6482 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c479 RSP: 002b:00007f61d1c66c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f61d1c676d4 RCX: 000000000045c479 RDX: 9999999999999999 RSI: 0000000000004c81 RDI: 0000000000000004 RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000006b5 R14: 00000000004c9318 R15: 000000000076bf2c INFO: task syz-executor.1:7903 blocked for more than 140 seconds. Not tainted 4.14.174-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D28776 7903 6483 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c479 RSP: 002b:00007f0fd9e95c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0fd9e966d4 RCX: 000000000045c479 RDX: 9999999999999999 RSI: 0000000000004c81 RDI: 0000000000000004 RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000006b5 R14: 00000000004c9318 R15: 000000000076bf2c Showing all locks held in the system: 1 lock held by khungtaskd/1047: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4544 2 locks held by syz-executor.4/6486: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x133/0x1030 fs/block_dev.c:1457 #1: (loop_index_mutex){+.+.}, at: [] lo_open+0x16/0xa0 drivers/block/loop.c:1634 2 locks held by syz-executor.5/6487: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x133/0x1030 fs/block_dev.c:1457 #1: (loop_index_mutex){+.+.}, at: [] lo_open+0x16/0xa0 drivers/block/loop.c:1634 2 locks held by syz-executor.3/6488: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x133/0x1030 fs/block_dev.c:1457 #1: (loop_index_mutex){+.+.}, at: [] lo_open+0x16/0xa0 drivers/block/loop.c:1634 2 locks held by systemd-udevd/7774: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_put+0xa5/0x730 fs/block_dev.c:1778 #1: (loop_index_mutex){+.+.}, at: [] lo_release+0x1a/0x180 drivers/block/loop.c:1677 2 locks held by syz-executor.2/7811: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [] lo_ioctl+0x8a/0x1c70 drivers/block/loop.c:1414 #1: (&bdev->bd_mutex){+.+.}, at: [] blkdev_reread_part+0x18/0x40 block/ioctl.c:192 2 locks held by syz-executor.2/7815: #0: (loop_index_mutex){+.+.}, at: [] loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 #1: (&lo->lo_ctl_mutex){+.+.}, at: [] loop_control_ioctl+0xf6/0x2b0 drivers/block/loop.c:2007 1 lock held by syz-executor.2/7851: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x133/0x1030 fs/block_dev.c:1457 1 lock held by syz-executor.2/7854: #0: (loop_index_mutex){+.+.}, at: [] loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 1 lock held by syz-executor.0/7824: #0: (loop_index_mutex){+.+.}, at: [] loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 1 lock held by syz-executor.1/7903: #0: (loop_index_mutex){+.+.}, at: [] loop_control_ioctl+0x6d/0x2b0 drivers/block/loop.c:1993 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1047 Comm: khungtaskd Not tainted 4.14.174-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe5/0x119 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:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x522/0xb40 kernel/hung_task.c:274 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 5975 Comm: rs:main Q:Reg Not tainted 4.14.174-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8880a7b1c2c0 task.stack: ffff8880a7af8000 RIP: 0010:percpu_up_read_preempt_enable include/linux/percpu-rwsem.h:100 [inline] RIP: 0010:percpu_up_read include/linux/percpu-rwsem.h:108 [inline] RIP: 0010:__sb_end_write+0x8b/0xd0 fs/super.c:1329 RSP: 0018:ffff8880a7affde8 EFLAGS: 00000297 RAX: 0000000080000000 RBX: ffff888215fe4938 RCX: 0000000000000000 RDX: 0000000000000004 RSI: ffffffff86d2eb60 RDI: ffffffff89a4eac0 RBP: ffff8880a7affdf0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000560 R11: 0000000000000000 R12: ffff8880a7b1c2c0 R13: 0000000000000002 R14: ffff888084a167b0 R15: ffff8880a8cffd60 FS: 00007fb4dfeb1700(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb4233c3000 CR3: 000000008cc28000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: file_end_write include/linux/fs.h:2721 [inline] vfs_write+0x221/0x4f0 fs/read_write.c:550 SYSC_write fs/read_write.c:590 [inline] SyS_write+0x100/0x250 fs/read_write.c:582 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x7fb4e28f51cd RSP: 002b:00007fb4dfeb0590 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fb4d4021850 RCX: 00007fb4e28f51cd RDX: 0000000000000560 RSI: 00007fb4d4021850 RDI: 0000000000000006 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 00007fb4d40215d0 R13: 00007fb4dfeb05b0 R14: 0000561acf560360 R15: 0000000000000560 Code: 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 4f 48 8b 43 70 65 ff 08 bf 01 00 00 00 e8 fc 56 b2 ff 65 8b 05 95 e6 75 7e <85> c0 74 22 48 8b 55 08 48 8d bb d8 00 00 00 be 01 00 00 00 e8