[ OK ] Started Getty on tty4. [ OK ] Started Serial Getty on ttyS0. [ OK ] Started Getty on tty1. [ OK ] Started Getty on tty3. [ OK ] Started Getty on tty2. [ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.17' (ECDSA) to the list of known hosts. syzkaller login: [ 76.117543][ T8440] [ 76.120107][ T8440] ====================================================== [ 76.127176][ T8440] WARNING: possible circular locking dependency detected [ 76.134387][ T8440] 5.13.0-rc2-next-20210518-syzkaller #0 Not tainted [ 76.141130][ T8440] ------------------------------------------------------ [ 76.148246][ T8440] syz-executor028/8440 is trying to acquire lock: [ 76.155186][ T8440] ffff88801a8ac5a0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x250/0x9e0 [ 76.164171][ T8440] [ 76.164171][ T8440] but task is already holding lock: [ 76.171641][ T8440] ffffffff8c9e4c70 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x222/0x9e0 [ 76.180603][ T8440] [ 76.180603][ T8440] which lock already depends on the new lock. [ 76.180603][ T8440] [ 76.191194][ T8440] [ 76.191194][ T8440] the existing dependency chain (in reverse order) is: [ 76.200656][ T8440] [ 76.200656][ T8440] -> #2 (bdev_lookup_sem){++++}-{3:3}: [ 76.208332][ T8440] down_write+0x92/0x150 [ 76.213203][ T8440] del_gendisk+0x222/0x9e0 [ 76.218227][ T8440] loop_control_ioctl+0x40d/0x4f0 [ 76.223773][ T8440] __x64_sys_ioctl+0x193/0x200 [ 76.229320][ T8440] do_syscall_64+0x31/0xb0 [ 76.234578][ T8440] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 76.241269][ T8440] [ 76.241269][ T8440] -> #1 (loop_ctl_mutex){+.+.}-{3:3}: [ 76.249173][ T8440] __mutex_lock+0x139/0x1120 [ 76.254301][ T8440] lo_open+0x1a/0x130 [ 76.259017][ T8440] __blkdev_get+0x135/0xa30 [ 76.264511][ T8440] blkdev_get_by_dev+0x200/0x660 [ 76.270075][ T8440] blkdev_open+0x154/0x2b0 [ 76.275495][ T8440] do_dentry_open+0x4b9/0x11c0 [ 76.281335][ T8440] path_openat+0x1c09/0x27d0 [ 76.286463][ T8440] do_filp_open+0x190/0x3d0 [ 76.291610][ T8440] do_sys_openat2+0x16d/0x420 [ 76.296928][ T8440] __x64_sys_open+0x119/0x1c0 [ 76.303159][ T8440] do_syscall_64+0x31/0xb0 [ 76.308231][ T8440] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 76.314920][ T8440] [ 76.314920][ T8440] -> #0 (&bdev->bd_mutex){+.+.}-{3:3}: [ 76.322559][ T8440] __lock_acquire+0x2a17/0x5230 [ 76.328322][ T8440] lock_acquire+0x1ab/0x740 [ 76.333700][ T8440] __mutex_lock+0x139/0x1120 [ 76.338807][ T8440] del_gendisk+0x250/0x9e0 [ 76.343742][ T8440] loop_control_ioctl+0x40d/0x4f0 [ 76.349283][ T8440] __x64_sys_ioctl+0x193/0x200 [ 76.354573][ T8440] do_syscall_64+0x31/0xb0 [ 76.359929][ T8440] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 76.366532][ T8440] [ 76.366532][ T8440] other info that might help us debug this: [ 76.366532][ T8440] [ 76.377169][ T8440] Chain exists of: [ 76.377169][ T8440] &bdev->bd_mutex --> loop_ctl_mutex --> bdev_lookup_sem [ 76.377169][ T8440] [ 76.390672][ T8440] Possible unsafe locking scenario: [ 76.390672][ T8440] [ 76.398571][ T8440] CPU0 CPU1 [ 76.404151][ T8440] ---- ---- [ 76.409841][ T8440] lock(bdev_lookup_sem); [ 76.414256][ T8440] lock(loop_ctl_mutex); [ 76.421247][ T8440] lock(bdev_lookup_sem); [ 76.428558][ T8440] lock(&bdev->bd_mutex); [ 76.432973][ T8440] [ 76.432973][ T8440] *** DEADLOCK *** [ 76.432973][ T8440] [ 76.441123][ T8440] 2 locks held by syz-executor028/8440: [ 76.446660][ T8440] #0: ffffffff8cc73448 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 [ 76.457212][ T8440] #1: ffffffff8c9e4c70 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x222/0x9e0 [ 76.467304][ T8440] [ 76.467304][ T8440] stack backtrace: [ 76.473323][ T8440] CPU: 0 PID: 8440 Comm: syz-executor028 Not tainted 5.13.0-rc2-next-20210518-syzkaller #0 [ 76.483563][ T8440] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 76.493888][ T8440] Call Trace: [ 76.497323][ T8440] dump_stack_lvl+0x13e/0x1d6 [ 76.502017][ T8440] check_noncircular+0x25f/0x2e0 [ 76.507249][ T8440] ? kernel_text_address+0xbd/0xf0 [ 76.512801][ T8440] ? print_circular_bug+0x1e0/0x1e0 [ 76.518529][ T8440] ? create_prof_cpu_mask+0x20/0x20 [ 76.524267][ T8440] ? arch_stack_walk+0x93/0xe0 [ 76.529638][ T8440] ? lockdep_lock+0xc6/0x200 [ 76.534247][ T8440] ? call_rcu_zapped+0xb0/0xb0 [ 76.539151][ T8440] __lock_acquire+0x2a17/0x5230 [ 76.544042][ T8440] ? lockdep_hardirqs_on_prepare+0x400/0x400 [ 76.550026][ T8440] lock_acquire+0x1ab/0x740 [ 76.554565][ T8440] ? del_gendisk+0x250/0x9e0 [ 76.559331][ T8440] ? lock_release+0x720/0x720 [ 76.564023][ T8440] ? lockdep_hardirqs_on_prepare+0x400/0x400 [ 76.570008][ T8440] __mutex_lock+0x139/0x1120 [ 76.574636][ T8440] ? del_gendisk+0x250/0x9e0 [ 76.580431][ T8440] ? del_gendisk+0x250/0x9e0 [ 76.585200][ T8440] ? mutex_lock_io_nested+0xf70/0xf70 [ 76.590579][ T8440] ? down_write+0xe0/0x150 [ 76.595080][ T8440] ? down_write_killable+0x170/0x170 [ 76.600561][ T8440] ? sysfs_remove_files+0x87/0xf0 [ 76.605630][ T8440] del_gendisk+0x250/0x9e0 [ 76.610920][ T8440] loop_control_ioctl+0x40d/0x4f0 [ 76.616544][ T8440] ? loop_lookup+0x1d0/0x1d0 [ 76.622289][ T8440] ? __sanitizer_cov_trace_const_cmp4+0x1c/0x70 [ 76.630587][ T8440] ? loop_lookup+0x1d0/0x1d0 [ 76.635464][ T8440] __x64_sys_ioctl+0x193/0x200 [ 76.640257][ T8440] do_syscall_64+0x31/0xb0 [ 76.644763][ T8440] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 76.650750][ T8440] RIP: 0033:0x43ee49 [ 76.655011][ T8440] Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 [ 76.675117][ T8440] RSP: 002b:00007fffe13e7618 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 76.684014][ T8440] RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ee49 [ 76.692262][ T8440] RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000003 [ 76.700551][ T8440] RBP: 0000000000402e30 R08: 0000000000000000 R09: 0000000000400488 [ 76.708650][ T8440] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402ec0 executing program [ 76.716942][ T8440] R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488