[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 38.954352][ T26] audit: type=1800 audit(1552755306.303:25): pid=7726 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 38.981649][ T26] audit: type=1800 audit(1552755306.303:26): pid=7726 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 39.016104][ T26] audit: type=1800 audit(1552755306.303:27): pid=7726 uid=0 auid=4294967295 ses=4294967295 subj==unconfined 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. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.39' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 49.516803][ T7880] [ 49.520383][ T7880] ====================================================== [ 49.527459][ T7880] WARNING: possible circular locking dependency detected [ 49.534560][ T7880] 5.0.0+ #25 Not tainted [ 49.538808][ T7880] ------------------------------------------------------ [ 49.546061][ T7880] syz-executor314/7880 is trying to acquire lock: [ 49.552458][ T7880] 000000004321900f (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 49.560555][ T7880] [ 49.560555][ T7880] but task is already holding lock: [ 49.567924][ T7880] 00000000d8761846 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 [ 49.577991][ T7880] [ 49.577991][ T7880] which lock already depends on the new lock. [ 49.577991][ T7880] [ 49.588403][ T7880] [ 49.588403][ T7880] the existing dependency chain (in reverse order) is: [ 49.597425][ T7880] [ 49.597425][ T7880] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 49.605243][ T7880] lock_acquire+0x16f/0x3f0 [ 49.610479][ T7880] __mutex_lock+0xf7/0x1310 [ 49.618868][ T7880] mutex_lock_interruptible_nested+0x16/0x20 [ 49.625365][ T7880] proc_pid_attr_write+0x200/0x580 [ 49.631016][ T7880] __vfs_write+0x8d/0x110 [ 49.635896][ T7880] __kernel_write+0x110/0x3b0 [ 49.641122][ T7880] write_pipe_buf+0x15d/0x1f0 [ 49.646345][ T7880] __splice_from_pipe+0x395/0x7d0 [ 49.651889][ T7880] splice_from_pipe+0x108/0x170 [ 49.657260][ T7880] default_file_splice_write+0x3c/0x90 [ 49.663231][ T7880] do_splice+0x70a/0x13c0 [ 49.668075][ T7880] __x64_sys_splice+0x2c6/0x330 [ 49.673442][ T7880] do_syscall_64+0x103/0x610 [ 49.678549][ T7880] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 49.684951][ T7880] [ 49.684951][ T7880] -> #0 (&pipe->mutex/1){+.+.}: [ 49.691990][ T7880] __lock_acquire+0x239c/0x3fb0 [ 49.697367][ T7880] lock_acquire+0x16f/0x3f0 [ 49.702410][ T7880] __mutex_lock+0xf7/0x1310 [ 49.707431][ T7880] mutex_lock_nested+0x16/0x20 [ 49.712707][ T7880] fifo_open+0x159/0xb00 [ 49.717507][ T7880] do_dentry_open+0x488/0x1160 [ 49.722801][ T7880] vfs_open+0xa0/0xd0 [ 49.727296][ T7880] path_openat+0x10e9/0x46e0 [ 49.732591][ T7880] do_filp_open+0x1a1/0x280 [ 49.737607][ T7880] do_open_execat+0x137/0x690 [ 49.742801][ T7880] __do_execve_file.isra.0+0x178d/0x23f0 [ 49.748973][ T7880] __x64_sys_execve+0x8f/0xc0 [ 49.754169][ T7880] do_syscall_64+0x103/0x610 [ 49.759272][ T7880] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 49.765668][ T7880] [ 49.765668][ T7880] other info that might help us debug this: [ 49.765668][ T7880] [ 49.775887][ T7880] Possible unsafe locking scenario: [ 49.775887][ T7880] [ 49.783324][ T7880] CPU0 CPU1 [ 49.788679][ T7880] ---- ---- [ 49.794031][ T7880] lock(&sig->cred_guard_mutex); [ 49.799040][ T7880] lock(&pipe->mutex/1); [ 49.805879][ T7880] lock(&sig->cred_guard_mutex); [ 49.813407][ T7880] lock(&pipe->mutex/1); [ 49.817728][ T7880] [ 49.817728][ T7880] *** DEADLOCK *** [ 49.817728][ T7880] [ 49.825864][ T7880] 1 lock held by syz-executor314/7880: [ 49.831301][ T7880] #0: 00000000d8761846 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 [ 49.841799][ T7880] [ 49.841799][ T7880] stack backtrace: [ 49.847717][ T7880] CPU: 1 PID: 7880 Comm: syz-executor314 Not tainted 5.0.0+ #25 [ 49.855338][ T7880] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 49.865397][ T7880] Call Trace: [ 49.868680][ T7880] dump_stack+0x172/0x1f0 [ 49.873004][ T7880] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 49.879083][ T7880] check_prev_add.constprop.0+0xf11/0x23c0 [ 49.884912][ T7880] ? depot_save_stack+0x1de/0x460 [ 49.889964][ T7880] ? check_usage+0x570/0x570 [ 49.894548][ T7880] ? mark_held_locks+0xa4/0xf0 [ 49.899306][ T7880] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 49.905131][ T7880] ? graph_lock+0x7b/0x200 [ 49.909747][ T7880] ? __lockdep_reset_lock+0x450/0x450 [ 49.915338][ T7880] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 49.921631][ T7880] __lock_acquire+0x239c/0x3fb0 [ 49.926525][ T7880] ? save_stack+0xa9/0xd0 [ 49.930854][ T7880] ? mark_held_locks+0xf0/0xf0 [ 49.935618][ T7880] lock_acquire+0x16f/0x3f0 [ 49.940119][ T7880] ? fifo_open+0x159/0xb00 [ 49.944530][ T7880] ? fifo_open+0x159/0xb00 [ 49.949038][ T7880] __mutex_lock+0xf7/0x1310 [ 49.953539][ T7880] ? fifo_open+0x159/0xb00 [ 49.957965][ T7880] ? fifo_open+0x159/0xb00 [ 49.962385][ T7880] ? fifo_open+0x2b5/0xb00 [ 49.966834][ T7880] ? mutex_trylock+0x1e0/0x1e0 [ 49.971593][ T7880] ? fifo_open+0x2b5/0xb00 [ 49.976017][ T7880] ? kasan_check_write+0x14/0x20 [ 49.980957][ T7880] ? lock_downgrade+0x880/0x880 [ 49.985820][ T7880] mutex_lock_nested+0x16/0x20 [ 49.990584][ T7880] ? mutex_lock_nested+0x16/0x20 [ 49.995563][ T7880] fifo_open+0x159/0xb00 [ 49.999805][ T7880] do_dentry_open+0x488/0x1160 [ 50.004596][ T7880] ? pipe_release+0x280/0x280 [ 50.009273][ T7880] ? chown_common+0x5c0/0x5c0 [ 50.013953][ T7880] ? inode_permission+0xb4/0x570 [ 50.018899][ T7880] vfs_open+0xa0/0xd0 [ 50.022888][ T7880] path_openat+0x10e9/0x46e0 [ 50.027524][ T7880] ? path_lookupat.isra.0+0x8d0/0x8d0 [ 50.032895][ T7880] ? __kmalloc+0x15c/0x740 [ 50.037301][ T7880] ? prepare_creds+0x2f5/0x3f0 [ 50.042094][ T7880] ? prepare_exec_creds+0x12/0xf0 [ 50.047134][ T7880] ? __do_execve_file.isra.0+0x393/0x23f0 [ 50.053028][ T7880] ? do_syscall_64+0x103/0x610 [ 50.058138][ T7880] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 50.064205][ T7880] ? __lock_acquire+0x548/0x3fb0 [ 50.069137][ T7880] ? prepare_exec_creds+0x12/0xf0 [ 50.074167][ T7880] ? __do_execve_file.isra.0+0x393/0x23f0 [ 50.080523][ T7880] ? __x64_sys_execve+0x8f/0xc0 [ 50.085397][ T7880] do_filp_open+0x1a1/0x280 [ 50.089900][ T7880] ? may_open_dev+0x100/0x100 [ 50.094727][ T7880] ? __lock_acquire+0x548/0x3fb0 [ 50.099668][ T7880] do_open_execat+0x137/0x690 [ 50.104376][ T7880] ? unregister_binfmt+0x170/0x170 [ 50.109501][ T7880] ? lock_downgrade+0x880/0x880 [ 50.114351][ T7880] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 50.120605][ T7880] ? kasan_check_read+0x11/0x20 [ 50.125469][ T7880] ? do_raw_spin_unlock+0x57/0x270 [ 50.130724][ T7880] __do_execve_file.isra.0+0x178d/0x23f0 [ 50.136437][ T7880] ? __sanitizer_cov_trace_cmp8+0x18/0x20 [ 50.142229][ T7880] ? __check_object_size+0x3d/0x42f [ 50.147516][ T7880] ? copy_strings_kernel+0x110/0x110 [ 50.156308][ T7880] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 50.162660][ T7880] ? getname_flags+0x277/0x5b0 [ 50.167526][ T7880] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 50.173664][ T7880] __x64_sys_execve+0x8f/0xc0 [ 50.178446][ T7880] do_syscall_64+0x103/0x610 [ 50.183141][ T7880] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 50.189142][ T7880] RIP: 0033:0x440289 [ 50.193092][ T7880] Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 50.214177][ T7880] RSP: 002b:00007ffe9e6c9b28 EFLAGS: 00000246 ORIG_RAX: 000000000000003b [ 50.222718][ T7880] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440289 [ 50.230948][ T7880] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000180 [ 50.239013][ T7880] RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 [ 50.247081][ T7880] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b10 [ 50.255093][ T7880] R13: 0000000000401ba0 R14: 0000000000000000 R15: 0000000000000000