bisecting fixing commit since f21b807c3cf8cd7c5ca9e406b27bf1cd2f1c1238 building syzkaller on 1ba81399e2d03b53a7e631c4ab05f25af1fb1911 testing commit f21b807c3cf8cd7c5ca9e406b27bf1cd2f1c1238 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.2 kernel signature: 8b21325b923fb20a897d5cf3ff1b49eb35e00ef1ffefe76ca64cf7567fdeef74 all runs: crashed: INFO: task hung in ext4_fill_super testing current HEAD ec681c53f8d2d0ee362ff67f5b98dd8263c15002 testing commit ec681c53f8d2d0ee362ff67f5b98dd8263c15002 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.2 kernel signature: f529a6cfa94d7113167c56c5558518c3b08a78928a70f8efb0ad9c3aeb59cf3c all runs: crashed: INFO: task hung in ext4_stop_mmpd revisions tested: 2, total time: 25m46.807934845s (build: 13m8.573033019s, test: 12m1.851549268s) the crash still happens on HEAD commit msg: Merge tag 'net-5.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net crash: INFO: task hung in ext4_stop_mmpd INFO: task syz-executor.5:9360 blocked for more than 143 seconds. Not tainted 5.15.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.5 state:D stack:27344 pid: 9360 ppid: 7045 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0x90d/0x26c0 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 schedule_timeout+0x19d/0x250 kernel/time/timer.c:1857 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+0x176/0x280 kernel/sched/completion.c:138 kthread_stop+0x104/0x4f0 kernel/kthread.c:648 ext4_stop_mmpd+0x34/0xb0 fs/ext4/mmp.c:255 ext4_fill_super+0x7cc8/0xb4f0 fs/ext4/super.c:5062 mount_bdev+0x2cb/0x3b0 fs/super.c:1368 legacy_get_tree+0xfa/0x1f0 fs/fs_context.c:610 vfs_get_tree+0x7f/0x2c0 fs/super.c:1498 do_new_mount fs/namespace.c:2988 [inline] path_mount+0x7e8/0x1a40 fs/namespace.c:3318 do_mount fs/namespace.c:3331 [inline] __do_sys_mount fs/namespace.c:3539 [inline] __se_sys_mount fs/namespace.c:3516 [inline] __x64_sys_mount+0x1f5/0x260 fs/namespace.c:3516 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x467afa RSP: 002b:00007fae7c786fa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000020000380 RCX: 0000000000467afa RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 00007fae7c787000 RBP: 00007fae7c787040 R08: 00007fae7c787040 R09: 0000000020000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020000000 R13: 00000000200000c0 R14: 00007fae7c787000 R15: 0000000020000200 INFO: task syz-executor.3:9374 blocked for more than 143 seconds. Not tainted 5.15.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.3 state:D stack:27840 pid: 9374 ppid: 7037 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0x90d/0x26c0 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 schedule_timeout+0x19d/0x250 kernel/time/timer.c:1857 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+0x176/0x280 kernel/sched/completion.c:138 kthread_stop+0x104/0x4f0 kernel/kthread.c:648 ext4_stop_mmpd+0x34/0xb0 fs/ext4/mmp.c:255 ext4_fill_super+0x7cc8/0xb4f0 fs/ext4/super.c:5062 mount_bdev+0x2cb/0x3b0 fs/super.c:1368 legacy_get_tree+0xfa/0x1f0 fs/fs_context.c:610 vfs_get_tree+0x7f/0x2c0 fs/super.c:1498 do_new_mount fs/namespace.c:2988 [inline] path_mount+0x7e8/0x1a40 fs/namespace.c:3318 do_mount fs/namespace.c:3331 [inline] __do_sys_mount fs/namespace.c:3539 [inline] __se_sys_mount fs/namespace.c:3516 [inline] __x64_sys_mount+0x1f5/0x260 fs/namespace.c:3516 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x467afa RSP: 002b:00007f3561ad2fa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000020000380 RCX: 0000000000467afa RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 00007f3561ad3000 RBP: 00007f3561ad3040 R08: 00007f3561ad3040 R09: 0000000020000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020000000 R13: 00000000200000c0 R14: 00007f3561ad3000 R15: 0000000020000200 INFO: task syz-executor.2:9438 blocked for more than 143 seconds. Not tainted 5.15.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.2 state:D stack:27840 pid: 9438 ppid: 7036 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0x90d/0x26c0 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 schedule_timeout+0x19d/0x250 kernel/time/timer.c:1857 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+0x176/0x280 kernel/sched/completion.c:138 kthread_stop+0x104/0x4f0 kernel/kthread.c:648 ext4_stop_mmpd+0x34/0xb0 fs/ext4/mmp.c:255 ext4_fill_super+0x7cc8/0xb4f0 fs/ext4/super.c:5062 mount_bdev+0x2cb/0x3b0 fs/super.c:1368 legacy_get_tree+0xfa/0x1f0 fs/fs_context.c:610 vfs_get_tree+0x7f/0x2c0 fs/super.c:1498 do_new_mount fs/namespace.c:2988 [inline] path_mount+0x7e8/0x1a40 fs/namespace.c:3318 do_mount fs/namespace.c:3331 [inline] __do_sys_mount fs/namespace.c:3539 [inline] __se_sys_mount fs/namespace.c:3516 [inline] __x64_sys_mount+0x1f5/0x260 fs/namespace.c:3516 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x467afa RSP: 002b:00007f7b7dc9efa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000020000380 RCX: 0000000000467afa RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 00007f7b7dc9f000 RBP: 00007f7b7dc9f040 R08: 00007f7b7dc9f040 R09: 0000000020000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020000000 R13: 00000000200000c0 R14: 00007f7b7dc9f000 R15: 0000000020000200 Showing all locks held in the system: 1 lock held by khungtaskd/27: #0: ffffffff8ab76840 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446 1 lock held by in:imklog/6204: #0: ffff888072957770 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x9c/0xb0 fs/file.c:990 1 lock held by syz-executor.5/9360: #0: ffff88806e6160e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x192/0xa00 fs/super.c:229 1 lock held by syz-executor.3/9374: #0: ffff888023eb40e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x192/0xa00 fs/super.c:229 1 lock held by syz-executor.2/9438: #0: ffff88807df6c0e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x192/0xa00 fs/super.c:229 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 27 Comm: khungtaskd Not tainted 5.15.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x57/0x7d lib/dump_stack.c:106 nmi_cpu_backtrace.cold+0x30/0xc0 lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace+0x11a/0x160 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline] watchdog+0x88c/0xbf0 kernel/hung_task.c:295 kthread+0x38b/0x460 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 2967 Comm: systemd-journal Not tainted 5.15.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__x64_sys_mkdir+0xc/0x120 fs/namei.c:3929 Code: c3 e8 d8 a3 f2 ff eb 98 e8 d1 a3 f2 ff eb ce e8 ca a3 f2 ff eb a8 0f 1f 84 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df 41 54 <55> 53 48 89 fb 48 83 c7 68 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 RSP: 0018:ffffc900020bff30 EFLAGS: 00000206 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff816abafa RDX: ffffffffffffffff RSI: 0000000000000008 RDI: ffffc900020bff58 RBP: ffffc900020bff48 R08: 0000000000000000 R09: ffff88807b41a01f R10: ffffed100f683403 R11: 0000000000000001 R12: ffffc900020bff58 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f7b2c1388c0(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7b29569030 CR3: 000000007aaa1000 CR4: 0000000000350ef0 Call Trace: do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f7b2b3f3687 Code: 00 b8 ff ff ff ff c3 0f 1f 40 00 48 8b 05 09 d8 2b 00 64 c7 00 5f 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 b8 53 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e1 d7 2b 00 f7 d8 64 89 01 48 RSP: 002b:00007ffca534a528 EFLAGS: 00000293 ORIG_RAX: 0000000000000053 RAX: ffffffffffffffda RBX: 00007ffca534d590 RCX: 00007f7b2b3f3687 RDX: 0000000000000000 RSI: 00000000000001ed RDI: 0000559b337558a0 RBP: 00007ffca534a560 R08: 0000559b32bb83e5 R09: 0000000000000018 R10: 0000000000000069 R11: 0000000000000293 R12: 0000000000000000 R13: 0000000000000001 R14: 0000559b337558a0 R15: 00007ffca534aba0 ---------------- Code disassembly (best guess): 0: c3 retq 1: e8 d8 a3 f2 ff callq 0xfff2a3de 6: eb 98 jmp 0xffffffa0 8: e8 d1 a3 f2 ff callq 0xfff2a3de d: eb ce jmp 0xffffffdd f: e8 ca a3 f2 ff callq 0xfff2a3de 14: eb a8 jmp 0xffffffbe 16: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 1d: 00 1e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 25: fc ff df 28: 41 54 push %r12 * 2a: 55 push %rbp <-- trapping instruction 2b: 53 push %rbx 2c: 48 89 fb mov %rdi,%rbx 2f: 48 83 c7 68 add $0x68,%rdi 33: 48 89 fa mov %rdi,%rdx 36: 48 c1 ea 03 shr $0x3,%rdx 3a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) 3e: 0f .byte 0xf 3f: 85 .byte 0x85