[ 38.926749] audit: type=1800 audit(1546907811.084:27): pid=7723 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0 [ 38.946021] audit: type=1800 audit(1546907811.084:28): pid=7723 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="ssh" dev="sda1" ino=2417 res=0 [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [ 39.387382] sshd (7790) used greatest stack depth: 19480 bytes left [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [ 39.590227] audit: type=1800 audit(1546907811.804:29): pid=7723 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="rc.local" dev="sda1" ino=2432 res=0 Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.30' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 57.691189] [ 57.692843] ====================================================== [ 57.699136] WARNING: possible circular locking dependency detected [ 57.705438] 5.0.0-rc1+ #14 Not tainted [ 57.709435] ------------------------------------------------------ [ 57.715740] syz-executor930/7878 is trying to acquire lock: [ 57.721435] 0000000076057489 (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 57.728792] [ 57.728792] but task is already holding lock: [ 57.734747] 00000000ab0ae55b (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 57.744104] [ 57.744104] which lock already depends on the new lock. [ 57.744104] [ 57.752398] [ 57.752398] the existing dependency chain (in reverse order) is: [ 57.760095] [ 57.760095] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 57.766496] __mutex_lock+0x12f/0x1670 [ 57.770912] mutex_lock_interruptible_nested+0x16/0x20 [ 57.776803] proc_pid_attr_write+0x1fa/0x530 [ 57.781727] __vfs_write+0x116/0xb40 [ 57.785953] __kernel_write+0x110/0x3b0 [ 57.790434] write_pipe_buf+0x180/0x240 [ 57.794912] __splice_from_pipe+0x39a/0x7e0 [ 57.799799] splice_from_pipe+0x1ea/0x310 [ 57.804468] default_file_splice_write+0x3c/0x90 [ 57.809726] do_splice+0x64b/0x1410 [ 57.813998] __x64_sys_splice+0x2c6/0x330 [ 57.818651] do_syscall_64+0x1a3/0x800 [ 57.823045] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 57.828845] [ 57.828845] -> #0 (&pipe->mutex/1){+.+.}: [ 57.834473] lock_acquire+0x1db/0x570 [ 57.838783] __mutex_lock+0x12f/0x1670 [ 57.843181] mutex_lock_nested+0x16/0x20 [ 57.847866] fifo_open+0x159/0xb00 [ 57.851911] do_dentry_open+0x48a/0x1210 [ 57.856474] vfs_open+0xa0/0xd0 [ 57.860387] path_openat+0x144f/0x5650 [ 57.864780] do_filp_open+0x26f/0x370 [ 57.869085] do_open_execat+0x20e/0x930 [ 57.873673] __do_execve_file.isra.0+0x1966/0x2700 [ 57.879114] __x64_sys_execve+0x8f/0xc0 [ 57.883595] do_syscall_64+0x1a3/0x800 [ 57.887989] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 57.893674] [ 57.893674] other info that might help us debug this: [ 57.893674] [ 57.901799] Possible unsafe locking scenario: [ 57.901799] [ 57.907938] CPU0 CPU1 [ 57.912586] ---- ---- [ 57.917309] lock(&sig->cred_guard_mutex); [ 57.921622] lock(&pipe->mutex/1); [ 57.927749] lock(&sig->cred_guard_mutex); [ 57.934571] lock(&pipe->mutex/1); [ 57.938186] [ 57.938186] *** DEADLOCK *** [ 57.938186] [ 57.944274] 1 lock held by syz-executor930/7878: [ 57.949057] #0: 00000000ab0ae55b (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 57.958854] [ 57.958854] stack backtrace: [ 57.963339] CPU: 0 PID: 7878 Comm: syz-executor930 Not tainted 5.0.0-rc1+ #14 [ 57.970597] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 57.980257] Call Trace: [ 57.982833] dump_stack+0x1db/0x2d0 [ 57.986441] ? dump_stack_print_info.cold+0x20/0x20 [ 57.991579] ? print_stack_trace+0x77/0xb0 [ 57.995887] ? vprintk_func+0x86/0x189 [ 57.999834] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 58.005194] __lock_acquire+0x3014/0x4a30 [ 58.009379] ? add_lock_to_list.isra.0+0x450/0x450 [ 58.014302] ? mark_held_locks+0x100/0x100 [ 58.018632] ? mark_held_locks+0xb1/0x100 [ 58.022774] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 58.027871] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 58.032961] ? lockdep_hardirqs_on+0x415/0x5d0 [ 58.037529] ? trace_hardirqs_off_caller+0x300/0x300 [ 58.042614] ? do_raw_spin_trylock+0x270/0x270 [ 58.047232] ? add_lock_to_list.isra.0+0x450/0x450 [ 58.052452] ? print_usage_bug+0xd0/0xd0 [ 58.056499] ? _raw_spin_unlock_irqrestore+0xa4/0xe0 [ 58.061587] ? __lock_is_held+0xb6/0x140 [ 58.065628] lock_acquire+0x1db/0x570 [ 58.069412] ? fifo_open+0x159/0xb00 [ 58.073109] ? ___might_sleep+0x1e7/0x310 [ 58.077233] ? lock_release+0xc40/0xc40 [ 58.081186] ? fifo_open+0x159/0xb00 [ 58.084878] ? fifo_open+0x159/0xb00 [ 58.088572] __mutex_lock+0x12f/0x1670 [ 58.092443] ? fifo_open+0x159/0xb00 [ 58.096252] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 58.101786] ? fifo_open+0x159/0xb00 [ 58.105493] ? check_preemption_disabled+0x48/0x290 [ 58.110512] ? lockdep_init_map+0x10c/0x5b0 [ 58.114867] ? mutex_trylock+0x2d0/0x2d0 [ 58.118926] ? add_lock_to_list.isra.0+0x450/0x450 [ 58.123840] ? __mutex_init+0x1f6/0x2a0 [ 58.127798] ? psi_task_change.cold+0x1ec/0x1ec [ 58.132447] ? fifo_open+0x2b5/0xb00 [ 58.136151] ? find_held_lock+0x35/0x120 [ 58.140195] ? fifo_open+0x2b5/0xb00 [ 58.143901] ? lock_acquire+0x1db/0x570 [ 58.147859] ? kasan_check_read+0x11/0x20 [ 58.151996] ? do_raw_spin_unlock+0xa0/0x330 [ 58.156391] ? do_raw_spin_trylock+0x270/0x270 [ 58.160965] mutex_lock_nested+0x16/0x20 [ 58.165114] ? _raw_spin_unlock+0x2d/0x50 [ 58.169259] ? mutex_lock_nested+0x16/0x20 [ 58.173485] fifo_open+0x159/0xb00 [ 58.177013] do_dentry_open+0x48a/0x1210 [ 58.181121] ? pipe_release+0x280/0x280 [ 58.185088] ? chown_common+0x740/0x740 [ 58.189062] ? security_inode_permission+0xd5/0x110 [ 58.194065] ? inode_permission+0xb4/0x570 [ 58.198283] vfs_open+0xa0/0xd0 [ 58.201548] path_openat+0x144f/0x5650 [ 58.205419] ? __lock_is_held+0xb6/0x140 [ 58.209470] ? path_lookupat.isra.0+0xba0/0xba0 [ 58.214123] ? __mutex_init+0x1f6/0x2a0 [ 58.218079] ? __lock_acquire+0x572/0x4a30 [ 58.222298] ? __do_execve_file.isra.0+0x47a/0x2700 [ 58.227305] ? __x64_sys_execve+0x8f/0xc0 [ 58.231444] ? do_syscall_64+0x1a3/0x800 [ 58.235506] do_filp_open+0x26f/0x370 [ 58.239292] ? may_open_dev+0x100/0x100 [ 58.243260] ? prepare_creds+0xa4/0x4e0 [ 58.247231] ? add_lock_to_list.isra.0+0x450/0x450 [ 58.252148] ? add_lock_to_list.isra.0+0x450/0x450 [ 58.257140] ? __do_execve_file.isra.0+0x901/0x2700 [ 58.262217] do_open_execat+0x20e/0x930 [ 58.266181] ? unregister_binfmt+0x2b0/0x2b0 [ 58.270578] ? kasan_check_read+0x11/0x20 [ 58.274719] ? do_raw_spin_trylock+0x270/0x270 [ 58.279292] ? __phys_addr_symbol+0x30/0x70 [ 58.283692] __do_execve_file.isra.0+0x1966/0x2700 [ 58.288612] ? copy_strings_kernel+0x110/0x110 [ 58.293178] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 58.298697] ? strncpy_from_user+0x3aa/0x4e0 [ 58.303100] ? digsig_verify.cold+0x32/0x32 [ 58.307412] ? kmem_cache_alloc+0x341/0x710 [ 58.311721] ? do_syscall_64+0x8c/0x800 [ 58.315687] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 58.321214] ? getname_flags+0x277/0x5b0 [ 58.325259] ? trace_hardirqs_off_caller+0x300/0x300 [ 58.330350] __x64_sys_execve+0x8f/0xc0 [ 58.334309] do_syscall_64+0x1a3/0x800 [ 58.338184] ? syscall_return_slowpath+0x5f0/0x5f0 [ 58.343099] ? prepare_exit_to_usermode+0x3b0/0x3b0 [ 58.348097] ? __switch_to_asm+0x34/0x70 [ 58.352139] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 58.357030] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 58.362215] RIP: 0033:0x445709 [ 58.365400] Code: e8 ec b8 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 8b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 58.384301] RSP: 002b:00007f66cf442d18 EFLAGS: 00000246 ORIG_RAX: 000000000000003b [ 58.391997] RAX: fffff