bisecting fixing commit since ddef1e8e3f6eb26034833b7255e3fa584d54a230 building syzkaller on 5ea87a6638e52a94361b26b8576a1605585815fb testing commit ddef1e8e3f6eb26034833b7255e3fa584d54a230 with gcc (GCC) 8.1.0 kernel signature: 50e3633b334060ff8f9554478f24e43155007a461b1be65d987499b915ec1e5c run #0: crashed: INFO: task hung in grab_super run #1: crashed: INFO: task hung in grab_super run #2: crashed: INFO: task hung in grab_super run #3: crashed: INFO: task hung in grab_super run #4: crashed: INFO: task hung in grab_super run #5: crashed: INFO: task hung in grab_super run #6: crashed: INFO: task hung in mount_bdev run #7: crashed: INFO: task hung in grab_super run #8: OK run #9: OK testing current HEAD 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae testing commit 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae with gcc (GCC) 8.1.0 kernel signature: 4ee9fcfafac09f426d89060c03f0c4c3a6d8514ca1bf815316ff5507f5a4e878 run #0: crashed: INFO: task hung in grab_super run #1: crashed: INFO: task hung in mount_bdev run #2: crashed: INFO: task hung in mount_bdev run #3: crashed: INFO: task hung in mount_bdev run #4: crashed: INFO: task hung in mount_bdev run #5: crashed: INFO: task hung in mount_bdev run #6: crashed: INFO: task hung in grab_super run #7: crashed: INFO: task hung in grab_super run #8: crashed: INFO: task hung in grab_super run #9: crashed: INFO: task hung in grab_super revisions tested: 2, total time: 37m3.827255843s (build: 16m53.505140021s, test: 19m28.969007916s) the crash still happens on HEAD commit msg: Linux 4.14.212 crash: INFO: task hung in grab_super print_req_error: I/O error, dev loop0, sector 256 UDF-fs: error (device loop0): udf_read_tagged: read failed, block=256, location=256 random: crng init done random: 7 urandom warning(s) missed due to ratelimiting INFO: task syz-executor.2:19219 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28488 19219 5577 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 __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:588 [inline] rwsem_down_write_failed+0x54f/0xb50 kernel/locking/rwsem-xadd.c:617 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105 __down_write arch/x86/include/asm/rwsem.h:126 [inline] down_write+0x53/0x90 kernel/locking/rwsem.c:56 grab_super+0x56/0x130 fs/super.c:373 sget_userns+0x687/0xb40 fs/super.c:504 sget+0xbe/0x100 fs/super.c:572 mount_bdev+0xc9/0x330 fs/super.c:1107 udf_mount+0x10/0x20 fs/udf/super.c:132 mount_fs+0x7f/0x269 fs/super.c:1237 vfs_kern_mount.part.33+0x58/0x3c0 fs/namespace.c:1046 vfs_kern_mount fs/namespace.c:1036 [inline] do_new_mount fs/namespace.c:2549 [inline] do_mount+0x36b/0x26a0 fs/namespace.c:2879 SYSC_mount fs/namespace.c:3095 [inline] SyS_mount+0xb8/0xd0 fs/namespace.c:3072 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x459fc9 RSP: 002b:00007f34bd72ac78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459fc9 RDX: 0000000020000040 RSI: 0000000020000240 RDI: 00000000200000c0 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f34bd72b6d4 R13: 00000000004c6a32 R14: 00000000004dbe98 R15: 00000000ffffffff INFO: task syz-executor.0:19224 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28488 19224 5586 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 mount_bdev+0x71/0x330 fs/super.c:1101 udf_mount+0x10/0x20 fs/udf/super.c:132 mount_fs+0x7f/0x269 fs/super.c:1237 vfs_kern_mount.part.33+0x58/0x3c0 fs/namespace.c:1046 vfs_kern_mount fs/namespace.c:1036 [inline] do_new_mount fs/namespace.c:2549 [inline] do_mount+0x36b/0x26a0 fs/namespace.c:2879 SYSC_mount fs/namespace.c:3095 [inline] SyS_mount+0xb8/0xd0 fs/namespace.c:3072 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x459fc9 RSP: 002b:00007fe56fd1ec78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459fc9 RDX: 0000000020000040 RSI: 0000000020000240 RDI: 00000000200000c0 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe56fd1f6d4 R13: 00000000004c6a32 R14: 00000000004dbe98 R15: 00000000ffffffff INFO: task syz-executor.4:19223 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28488 19223 5582 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 mount_bdev+0x71/0x330 fs/super.c:1101 udf_mount+0x10/0x20 fs/udf/super.c:132 mount_fs+0x7f/0x269 fs/super.c:1237 vfs_kern_mount.part.33+0x58/0x3c0 fs/namespace.c:1046 vfs_kern_mount fs/namespace.c:1036 [inline] do_new_mount fs/namespace.c:2549 [inline] do_mount+0x36b/0x26a0 fs/namespace.c:2879 SYSC_mount fs/namespace.c:3095 [inline] SyS_mount+0xb8/0xd0 fs/namespace.c:3072 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x459fc9 RSP: 002b:00007faf62ac7c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459fc9 RDX: 0000000020000040 RSI: 0000000020000240 RDI: 00000000200000c0 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007faf62ac86d4 R13: 00000000004c6a32 R14: 00000000004dbe98 R15: 00000000ffffffff INFO: task syz-executor.3:19240 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D28488 19240 5579 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 mount_bdev+0x71/0x330 fs/super.c:1101 udf_mount+0x10/0x20 fs/udf/super.c:132 mount_fs+0x7f/0x269 fs/super.c:1237 vfs_kern_mount.part.33+0x58/0x3c0 fs/namespace.c:1046 vfs_kern_mount fs/namespace.c:1036 [inline] do_new_mount fs/namespace.c:2549 [inline] do_mount+0x36b/0x26a0 fs/namespace.c:2879 SYSC_mount fs/namespace.c:3095 [inline] SyS_mount+0xb8/0xd0 fs/namespace.c:3072 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x459fc9 RSP: 002b:00007f9a0bf43c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459fc9 RDX: 0000000020000040 RSI: 0000000020000240 RDI: 00000000200000c0 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9a0bf446d4 R13: 00000000004c6a32 R14: 00000000004dbe98 R15: 00000000ffffffff INFO: task syz-executor.5:19246 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D28488 19246 5584 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 mount_bdev+0x71/0x330 fs/super.c:1101 udf_mount+0x10/0x20 fs/udf/super.c:132 mount_fs+0x7f/0x269 fs/super.c:1237 vfs_kern_mount.part.33+0x58/0x3c0 fs/namespace.c:1046 vfs_kern_mount fs/namespace.c:1036 [inline] do_new_mount fs/namespace.c:2549 [inline] do_mount+0x36b/0x26a0 fs/namespace.c:2879 SYSC_mount fs/namespace.c:3095 [inline] SyS_mount+0xb8/0xd0 fs/namespace.c:3072 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x459fc9 RSP: 002b:00007fe230464c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459fc9 RDX: 0000000020000040 RSI: 0000000020000240 RDI: 00000000200000c0 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe2304656d4 R13: 00000000004c6a32 R14: 00000000004dbe98 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1021: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4548 2 locks held by syz-executor.2/19219: #0: (&bdev->bd_fsfreeze_mutex){+.+.}, at: [] mount_bdev+0x71/0x330 fs/super.c:1101 #1: (&type->s_umount_key#48){+.+.}, at: [] grab_super+0x56/0x130 fs/super.c:373 1 lock held by syz-executor.0/19224: #0: (&bdev->bd_fsfreeze_mutex){+.+.}, at: [] mount_bdev+0x71/0x330 fs/super.c:1101 1 lock held by syz-executor.4/19223: #0: (&bdev->bd_fsfreeze_mutex){+.+.}, at: [] mount_bdev+0x71/0x330 fs/super.c:1101 1 lock held by syz-executor.3/19240: #0: (&bdev->bd_fsfreeze_mutex){+.+.}, at: [] mount_bdev+0x71/0x330 fs/super.c:1101 1 lock held by syz-executor.5/19246: #0: (&bdev->bd_fsfreeze_mutex){+.+.}, at: [] mount_bdev+0x71/0x330 fs/super.c:1101 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1021 Comm: khungtaskd Not tainted 4.14.212-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+0xe6/0x11a 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 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 19218 Comm: syz-executor.1 Not tainted 4.14.212-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8881de5a45c0 task.stack: ffff8881f3890000 RIP: 0010:__lock_release kernel/locking/lockdep.c:3744 [inline] RIP: 0010:lock_release+0x1c7/0x830 kernel/locking/lockdep.c:4017 RSP: 0018:ffff8881f3897520 EFLAGS: 00000097 RAX: 0000000000000003 RBX: 1ffff1103e712ea8 RCX: 1ffffffff0edbbad RDX: 0000000000000004 RSI: 0000000000000001 RDI: ffffffff87cb6420 RBP: ffff8881f38975c8 R08: 0000000000000001 R09: 0000000000000000 R10: ffff8881f3897580 R11: 0000000000000040 R12: ffff8881de5a45c0 R13: ffffffff87990920 R14: ffff8881ce723028 R15: ffff8881de5a45c0 FS: 00007f74ef2a3700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1f74032038 CR3: 00000001e8d45003 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_lock_release include/linux/rcupdate.h:247 [inline] rcu_read_unlock include/linux/rcupdate.h:685 [inline] find_get_entry+0xf4/0x460 mm/filemap.c:1392 pagecache_get_page+0x45/0x5a0 mm/filemap.c:1465 find_or_create_page include/linux/pagemap.h:326 [inline] grow_dev_page fs/buffer.c:1004 [inline] grow_buffers fs/buffer.c:1077 [inline] __getblk_slow fs/buffer.c:1104 [inline] __getblk_gfp+0x1e8/0x5f0 fs/buffer.c:1383 __bread_gfp+0xa/0x210 fs/buffer.c:1428 sb_bread include/linux/buffer_head.h:309 [inline] udf_tread+0xe3/0x140 fs/udf/misc.c:44 udf_read_tagged+0x2b/0x470 fs/udf/misc.c:210 udf_check_anchor_block+0x185/0x5f0 fs/udf/super.c:1816 udf_scan_anchors+0x3a3/0x520 fs/udf/super.c:1895 udf_find_anchor fs/udf/super.c:1913 [inline] udf_load_vrs+0x576/0xa00 fs/udf/super.c:1978 udf_fill_super+0x6c4/0x1472 fs/udf/super.c:2170 mount_bdev+0x278/0x330 fs/super.c:1134 udf_mount+0x10/0x20 fs/udf/super.c:132 mount_fs+0x7f/0x269 fs/super.c:1237 vfs_kern_mount.part.33+0x58/0x3c0 fs/namespace.c:1046 vfs_kern_mount fs/namespace.c:1036 [inline] do_new_mount fs/namespace.c:2549 [inline] do_mount+0x36b/0x26a0 fs/namespace.c:2879 SYSC_mount fs/namespace.c:3095 [inline] SyS_mount+0xb8/0xd0 fs/namespace.c:3072 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x459fc9 RSP: 002b:00007f74ef2a2c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459fc9 RDX: 0000000020000040 RSI: 0000000020000240 RDI: 00000000200000c0 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f74ef2a36d4 R13: 00000000004c6a32 R14: 00000000004dbe98 R15: 00000000ffffffff Code: ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 65 4c 8b 3c 25 40 ee 01 00 38 d0 7c 08 84 d2 0f 85 82 05 00 00 44 8b 05 19 24 84 06 <45> 85 c0 0f 84 f9 01 00 00 49 8d 87 80 08 00 00 48 89 c2 48 89