[ 39.824879] audit: type=1800 audit(1546275605.743:25): pid=7870 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 39.862260] audit: type=1800 audit(1546275605.743:26): pid=7870 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 39.895987] audit: type=1800 audit(1546275605.743:27): pid=7870 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0 [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [....] startpar: service(s) returned failure: rsyslog ...[?25l[?1c7[FAIL8[?25h[?0c failed! Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.10.43' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 47.912231] [ 47.913892] ====================================================== [ 47.920189] WARNING: possible circular locking dependency detected [ 47.926488] 4.20.0+ #1 Not tainted [ 47.930005] ------------------------------------------------------ [ 47.936306] syz-executor346/8044 is trying to acquire lock: [ 47.942027] 000000004032f654 (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 47.949389] [ 47.949389] but task is already holding lock: [ 47.955349] 00000000620362e7 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x55/0x120 [ 47.964103] [ 47.964103] which lock already depends on the new lock. [ 47.964103] [ 47.972400] [ 47.972400] the existing dependency chain (in reverse order) is: [ 47.980001] [ 47.980001] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 47.986326] __mutex_lock+0x12f/0x1670 [ 47.990721] mutex_lock_interruptible_nested+0x16/0x20 [ 47.996509] proc_pid_attr_write+0x1fa/0x530 [ 48.001427] __vfs_write+0x116/0xb40 [ 48.005644] __kernel_write+0x110/0x3b0 [ 48.010124] write_pipe_buf+0x180/0x240 [ 48.014604] __splice_from_pipe+0x39a/0x7e0 [ 48.019449] splice_from_pipe+0x1ea/0x310 [ 48.024104] default_file_splice_write+0x3c/0x90 [ 48.029365] do_splice+0x64b/0x1410 [ 48.033512] __x64_sys_splice+0x2c6/0x330 [ 48.038178] do_syscall_64+0x1a3/0x800 [ 48.042576] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 48.048275] [ 48.048275] -> #0 (&pipe->mutex/1){+.+.}: [ 48.053896] lock_acquire+0x1db/0x570 [ 48.058203] __mutex_lock+0x12f/0x1670 [ 48.062596] mutex_lock_nested+0x16/0x20 [ 48.067164] fifo_open+0x159/0xb00 [ 48.071235] do_dentry_open+0x48a/0x1210 [ 48.075802] vfs_open+0xa0/0xd0 [ 48.079583] path_openat+0x144f/0x5650 [ 48.083996] do_filp_open+0x26f/0x370 [ 48.088303] do_open_execat+0x20e/0x930 [ 48.092785] __do_execve_file.isra.0+0x181e/0x2510 [ 48.098222] __x64_sys_execve+0x8f/0xc0 [ 48.102701] do_syscall_64+0x1a3/0x800 [ 48.107096] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 48.112785] [ 48.112785] other info that might help us debug this: [ 48.112785] [ 48.120926] Possible unsafe locking scenario: [ 48.120926] [ 48.126983] CPU0 CPU1 [ 48.131629] ---- ---- [ 48.136286] lock(&sig->cred_guard_mutex); [ 48.140591] lock(&pipe->mutex/1); [ 48.146719] lock(&sig->cred_guard_mutex); [ 48.153543] lock(&pipe->mutex/1); [ 48.157172] [ 48.157172] *** DEADLOCK *** [ 48.157172] [ 48.163223] 1 lock held by syz-executor346/8044: [ 48.167965] #0: 00000000620362e7 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x55/0x120 [ 48.177150] [ 48.177150] stack backtrace: [ 48.181633] CPU: 0 PID: 8044 Comm: syz-executor346 Not tainted 4.20.0+ #1 [ 48.188544] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 48.197885] Call Trace: [ 48.200479] dump_stack+0x1db/0x2d0 [ 48.204093] ? dump_stack_print_info.cold+0x20/0x20 [ 48.209113] ? print_stack_trace+0x77/0xb0 [ 48.213356] ? vprintk_func+0x86/0x189 [ 48.217237] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 48.222602] __lock_acquire+0x3014/0x4a30 [ 48.226733] ? add_lock_to_list.isra.0+0x450/0x450 [ 48.231648] ? is_bpf_text_address+0xac/0x170 [ 48.236130] ? mark_held_locks+0x100/0x100 [ 48.240348] ? mark_held_locks+0xb1/0x100 [ 48.244486] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 48.249574] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 48.254661] ? lockdep_hardirqs_on+0x415/0x5d0 [ 48.259238] ? trace_hardirqs_off_caller+0x300/0x300 [ 48.264325] ? do_raw_spin_trylock+0x270/0x270 [ 48.268889] ? add_lock_to_list.isra.0+0x450/0x450 [ 48.273803] ? print_usage_bug+0xd0/0xd0 [ 48.277848] ? _raw_spin_unlock_irqrestore+0xa4/0xe0 [ 48.282957] ? __lock_is_held+0xb6/0x140 [ 48.287008] lock_acquire+0x1db/0x570 [ 48.290794] ? fifo_open+0x159/0xb00 [ 48.294494] ? ___might_sleep+0x1e7/0x310 [ 48.298633] ? lock_release+0xc40/0xc40 [ 48.302594] ? fifo_open+0x159/0xb00 [ 48.306292] ? fifo_open+0x159/0xb00 [ 48.310008] __mutex_lock+0x12f/0x1670 [ 48.313879] ? fifo_open+0x159/0xb00 [ 48.317596] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 48.323117] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 48.328637] ? fifo_open+0x159/0xb00 [ 48.332334] ? lockdep_init_map+0x10c/0x5b0 [ 48.336641] ? mutex_trylock+0x2d0/0x2d0 [ 48.340683] ? add_lock_to_list.isra.0+0x450/0x450 [ 48.345597] ? __mutex_init+0x1f6/0x2a0 [ 48.349569] ? psi_task_change.cold+0x1ec/0x1ec [ 48.354236] ? fifo_open+0x2b5/0xb00 [ 48.357934] ? find_held_lock+0x35/0x120 [ 48.361978] ? fifo_open+0x2b5/0xb00 [ 48.365676] ? lock_acquire+0x1db/0x570 [ 48.369639] ? kasan_check_read+0x11/0x20 [ 48.373773] ? do_raw_spin_unlock+0xa0/0x330 [ 48.378165] ? do_raw_spin_trylock+0x270/0x270 [ 48.382753] mutex_lock_nested+0x16/0x20 [ 48.386799] ? _raw_spin_unlock+0x2d/0x50 [ 48.390931] ? mutex_lock_nested+0x16/0x20 [ 48.395148] fifo_open+0x159/0xb00 [ 48.398674] do_dentry_open+0x48a/0x1210 [ 48.402718] ? pipe_release+0x280/0x280 [ 48.406678] ? chown_common+0x740/0x740 [ 48.410637] ? security_inode_permission+0xd5/0x110 [ 48.415642] ? inode_permission+0xb4/0x570 [ 48.419864] vfs_open+0xa0/0xd0 [ 48.423130] path_openat+0x144f/0x5650 [ 48.427003] ? add_lock_to_list.isra.0+0x450/0x450 [ 48.431920] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 48.437463] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 48.442993] ? path_lookupat.isra.0+0xba0/0xba0 [ 48.447648] ? psi_task_change.cold+0x1ec/0x1ec [ 48.452303] ? __lock_acquire+0x572/0x4a30 [ 48.456523] ? __x64_sys_execve+0x8f/0xc0 [ 48.460659] ? new_task_smack+0x26a/0x330 [ 48.464796] do_filp_open+0x26f/0x370 [ 48.468578] ? may_open_dev+0x100/0x100 [ 48.472537] ? smack_cred_alloc_blank+0x80/0x80 [ 48.477190] ? add_lock_to_list.isra.0+0x450/0x450 [ 48.482102] ? add_lock_to_list.isra.0+0x450/0x450 [ 48.487018] ? refcount_add_not_zero_checked+0x330/0x330 [ 48.492472] ? prepare_creds+0xa4/0x4e0 [ 48.496434] ? prepare_creds+0xa4/0x4e0 [ 48.500398] ? __do_execve_file.isra.0+0x908/0x2510 [ 48.505429] do_open_execat+0x20e/0x930 [ 48.509507] ? unregister_binfmt+0x2b0/0x2b0 [ 48.513912] ? kasan_check_read+0x11/0x20 [ 48.518067] ? do_raw_spin_trylock+0x270/0x270 [ 48.522634] ? key_put+0x36/0x90 [ 48.525996] __do_execve_file.isra.0+0x181e/0x2510 [ 48.530910] ? prepare_bprm_creds+0x120/0x120 [ 48.535398] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 48.540936] ? strncpy_from_user+0x317/0x440 [ 48.545337] ? digsig_verify.cold+0x32/0x32 [ 48.549646] ? kmem_cache_alloc+0x341/0x710 [ 48.553977] ? do_syscall_64+0x8c/0x800 [ 48.557942] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 48.563479] ? getname_flags+0x277/0x5b0 [ 48.567541] ? trace_hardirqs_off_caller+0x300/0x300 [ 48.572630] __x64_sys_execve+0x8f/0xc0 [ 48.576591] do_syscall_64+0x1a3/0x800 [ 48.580461] ? syscall_return_slowpath+0x5f0/0x5f0 [ 48.585378] ? prepare_exit_to_usermode+0x232/0x3b0 [ 48.590396] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 48.595229] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 48.600402] RIP: 0033:0x445719 [ 48.603583] Code: e8 6c b6 02 00 48 83 c4 18 c3 0f 1f 80 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 0f 83 2b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 48.622475] RSP: 002b:00007f2916aafda8 EFLAGS: 00000246 ORIG_RAX: 000000000000003b [ 48.630169] RAX: ffffffffffffffda RBX: 00000000006dac58 RCX: 0000000000445719 [ 48.637422] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000340 [ 48.644687] RBP: 00000000006dac50 R08: 0000000000000000 R09: 0000000000000000 [ 48.651944] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac5c [ 48.659198] R13: 0030656c69662f2e R14: 68742f636f72702f R15: 00000000006