[ OK ] Started Regular background program processing daemon. [ OK ] Started Daily Cleanup of Temporary Directories. [ OK ] Reached target Timers. Starting Permit User Sessions... [ OK ] Started System Logging Service. [ 63.844093][ T8114] sshd (8114) used greatest stack depth: 22640 bytes left [ OK ] Started Permit User Sessions. [ OK ] Found device /dev/ttyS0. [ OK ] Started OpenBSD Secure Shell server. [ OK ] Started getty on tty2-tty6 if dbus and logind are not available. [ OK ] Listening on Load/Save RF Kill Switch Status /dev/rfkill Watch. [ OK ] Started Getty on tty6. [ OK ] Started Getty on tty5. [ OK ] Started Getty on tty4. [ OK ] Started Getty on tty3. [ OK ] Started Getty on tty2. [ OK ] Started Serial Getty on ttyS0. [ OK ] Started Getty on tty1. [ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... Starting Load/Save RF Kill Switch Status... [ OK ] Started Update UTMP about System Runlevel Changes. [ OK ] Started Load/Save RF Kill Switch Status. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.192' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 83.714870][ T37] audit: type=1400 audit(1623262594.985:8): avc: denied { execmem } for pid=8425 comm="syz-executor939" scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=process permissive=1 [ 83.718352][ T8425] [ 83.737907][ T8425] ====================================================== [ 83.745176][ T8425] WARNING: possible circular locking dependency detected [ 83.752740][ T8425] 5.13.0-rc5-syzkaller #0 Not tainted [ 83.758107][ T8425] ------------------------------------------------------ [ 83.765319][ T8425] syz-executor939/8425 is trying to acquire lock: [ 83.772113][ T8425] ffff88801b5710e0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x24b/0xa00 [ 83.781141][ T8425] [ 83.781141][ T8425] but task is already holding lock: [ 83.788607][ T8425] ffffffff8ca6c628 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 [ 83.798164][ T8425] [ 83.798164][ T8425] which lock already depends on the new lock. [ 83.798164][ T8425] [ 83.808559][ T8425] [ 83.808559][ T8425] the existing dependency chain (in reverse order) is: [ 83.817842][ T8425] [ 83.817842][ T8425] -> #1 (loop_ctl_mutex){+.+.}-{3:3}: [ 83.825408][ T8425] __mutex_lock+0x139/0x10c0 [ 83.830538][ T8425] lo_open+0x1a/0x130 [ 83.835161][ T8425] __blkdev_get+0x182/0xa30 [ 83.840513][ T8425] blkdev_get_by_dev+0x200/0x660 [ 83.846079][ T8425] blkdev_open+0x154/0x2b0 [ 83.851565][ T8425] do_dentry_open+0x4b9/0x11b0 [ 83.857383][ T8425] path_openat+0x1c0e/0x27e0 [ 83.862697][ T8425] do_filp_open+0x190/0x3d0 [ 83.868833][ T8425] do_sys_openat2+0x16d/0x420 [ 83.874119][ T8425] __x64_sys_open+0x119/0x1c0 [ 83.879319][ T8425] do_syscall_64+0x3a/0xb0 [ 83.884362][ T8425] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 83.890895][ T8425] [ 83.890895][ T8425] -> #0 (&bdev->bd_mutex){+.+.}-{3:3}: [ 83.898522][ T8425] __lock_acquire+0x2a17/0x5230 [ 83.904574][ T8425] lock_acquire+0x1ab/0x740 [ 83.909637][ T8425] __mutex_lock+0x139/0x10c0 [ 83.914751][ T8425] del_gendisk+0x24b/0xa00 [ 83.919855][ T8425] loop_control_ioctl+0x40d/0x4f0 [ 83.925527][ T8425] __x64_sys_ioctl+0x193/0x200 [ 83.930841][ T8425] do_syscall_64+0x3a/0xb0 [ 83.936144][ T8425] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 83.942711][ T8425] [ 83.942711][ T8425] other info that might help us debug this: [ 83.942711][ T8425] [ 83.953046][ T8425] Possible unsafe locking scenario: [ 83.953046][ T8425] [ 83.960657][ T8425] CPU0 CPU1 [ 83.966102][ T8425] ---- ---- [ 83.971573][ T8425] lock(loop_ctl_mutex); [ 83.976396][ T8425] lock(&bdev->bd_mutex); [ 83.983325][ T8425] lock(loop_ctl_mutex); [ 83.990274][ T8425] lock(&bdev->bd_mutex); [ 83.994885][ T8425] [ 83.994885][ T8425] *** DEADLOCK *** [ 83.994885][ T8425] [ 84.003173][ T8425] 1 lock held by syz-executor939/8425: [ 84.009140][ T8425] #0: ffffffff8ca6c628 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_control_ioctl+0x7b/0x4f0 [ 84.019245][ T8425] [ 84.019245][ T8425] stack backtrace: [ 84.025252][ T8425] CPU: 0 PID: 8425 Comm: syz-executor939 Not tainted 5.13.0-rc5-syzkaller #0 [ 84.034240][ T8425] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 84.044313][ T8425] Call Trace: [ 84.048008][ T8425] dump_stack+0x141/0x1d7 [ 84.052538][ T8425] check_noncircular+0x25f/0x2e0 [ 84.057483][ T8425] ? kasan_save_stack+0x32/0x40 [ 84.062338][ T8425] ? print_circular_bug+0x1e0/0x1e0 [ 84.067650][ T8425] ? __kasan_slab_free+0xcd/0x100 [ 84.072896][ T8425] ? kernfs_put.part.0+0x2c4/0x540 [ 84.078180][ T8425] ? kernfs_put+0x42/0x50 [ 84.082509][ T8425] ? __kernfs_remove+0x703/0xa90 [ 84.087530][ T8425] ? kernfs_remove_by_name_ns+0x51/0xb0 [ 84.093089][ T8425] ? sysfs_remove_files+0x87/0xf0 [ 84.098118][ T8425] ? lockdep_lock+0xc6/0x200 [ 84.102705][ T8425] ? call_rcu_zapped+0xb0/0xb0 [ 84.107589][ T8425] ? find_held_lock+0x2d/0x110 [ 84.112355][ T8425] __lock_acquire+0x2a17/0x5230 [ 84.117369][ T8425] ? lockdep_hardirqs_on_prepare+0x400/0x400 [ 84.123338][ T8425] lock_acquire+0x1ab/0x740 [ 84.128004][ T8425] ? del_gendisk+0x24b/0xa00 [ 84.132697][ T8425] ? lock_release+0x720/0x720 [ 84.137487][ T8425] ? find_held_lock+0x2d/0x110 [ 84.142248][ T8425] __mutex_lock+0x139/0x10c0 [ 84.146827][ T8425] ? del_gendisk+0x24b/0xa00 [ 84.151406][ T8425] ? mutex_lock_io_nested+0xf20/0xf20 [ 84.157025][ T8425] ? del_gendisk+0x24b/0xa00 [ 84.161707][ T8425] ? __mutex_unlock_slowpath+0xe2/0x610 [ 84.167243][ T8425] ? mutex_lock_io_nested+0xf20/0xf20 [ 84.172631][ T8425] ? wait_for_completion_io+0x270/0x270 [ 84.178270][ T8425] ? __sanitizer_cov_trace_const_cmp4+0x1c/0x70 [ 84.184505][ T8425] ? kernfs_remove_by_name_ns+0x62/0xb0 [ 84.190032][ T8425] ? sysfs_remove_files+0x87/0xf0 [ 84.195057][ T8425] del_gendisk+0x24b/0xa00 [ 84.199478][ T8425] loop_control_ioctl+0x40d/0x4f0 [ 84.204508][ T8425] ? loop_lookup+0x1d0/0x1d0 [ 84.209101][ T8425] ? security_file_ioctl+0x5c/0xb0 [ 84.214202][ T8425] ? __sanitizer_cov_trace_const_cmp4+0x1c/0x70 [ 84.220530][ T8425] ? loop_lookup+0x1d0/0x1d0 [ 84.225134][ T8425] __x64_sys_ioctl+0x193/0x200 [ 84.229888][ T8425] do_syscall_64+0x3a/0xb0 [ 84.234380][ T8425] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 84.240271][ T8425] RIP: 0033:0x43ee49 [ 84.244152][ T8425] 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 [ 84.264429][ T8425] RSP: 002b:00007fff8b0aed68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 84.273711][ T8425] RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ee49 [ 84.281855][ T8425] RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000003 [ 84.289944][ T8425] RBP: 0000000000402e30 R08: 0000000000000000 R09: 0000000000400488 [ 84.297948][ T8425] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402ec0 [ 84.306443][ T8425] R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488