[ 38.081014] audit: type=1800 audit(1550638858.439:26): pid=7691 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 38.106659] audit: type=1800 audit(1550638858.449:27): pid=7691 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0 [ 38.129990] audit: type=1800 audit(1550638858.449:28): pid=7691 uid=0 auid=4294967295 ses=4294967295 subj==unconfined 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. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [ 38.894170] audit: type=1800 audit(1550638859.289:29): pid=7691 uid=0 auid=4294967295 ses=4294967295 subj==unconfined 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 '10.128.0.121' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 47.469120] [ 47.470767] ====================================================== [ 47.477064] WARNING: possible circular locking dependency detected [ 47.483366] 5.0.0-rc7+ #80 Not tainted [ 47.487230] ------------------------------------------------------ [ 47.493526] syz-executor638/7846 is trying to acquire lock: [ 47.499215] 0000000041ad1ae1 (&sig->cred_guard_mutex){+.+.}, at: proc_pid_attr_write+0x1fa/0x530 [ 47.508136] [ 47.508136] but task is already holding lock: [ 47.514098] 000000002040eaf3 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 [ 47.521302] [ 47.521302] which lock already depends on the new lock. [ 47.521302] [ 47.529594] [ 47.529594] the existing dependency chain (in reverse order) is: [ 47.537191] [ 47.537191] -> #1 (&pipe->mutex/1){+.+.}: [ 47.542821] __mutex_lock+0xf7/0x1310 [ 47.547128] mutex_lock_nested+0x16/0x20 [ 47.551692] fifo_open+0x159/0xb00 [ 47.555740] do_dentry_open+0x47d/0x1130 [ 47.560301] vfs_open+0xa0/0xd0 [ 47.564090] path_openat+0x10d7/0x4690 [ 47.568483] do_filp_open+0x1a1/0x280 [ 47.572792] do_open_execat+0x13b/0x6d0 [ 47.577295] __do_execve_file.isra.0+0x178d/0x23f0 [ 47.582738] __ia32_compat_sys_execve+0x94/0xc0 [ 47.587923] do_fast_syscall_32+0x281/0xc98 [ 47.592752] entry_SYSENTER_compat+0x70/0x7f [ 47.597673] [ 47.597673] -> #0 (&sig->cred_guard_mutex){+.+.}: [ 47.603982] lock_acquire+0x16f/0x3f0 [ 47.608331] __mutex_lock+0xf7/0x1310 [ 47.612636] mutex_lock_interruptible_nested+0x16/0x20 [ 47.618419] proc_pid_attr_write+0x1fa/0x530 [ 47.623328] __vfs_write+0x116/0x8e0 [ 47.627550] __kernel_write+0x110/0x3b0 [ 47.632042] write_pipe_buf+0x15d/0x1f0 [ 47.636537] __splice_from_pipe+0x39a/0x7e0 [ 47.641375] splice_from_pipe+0x108/0x170 [ 47.646038] default_file_splice_write+0x3c/0x90 [ 47.651310] do_splice+0x644/0x1330 [ 47.655452] __ia32_sys_splice+0x2c4/0x330 [ 47.660204] do_fast_syscall_32+0x281/0xc98 [ 47.665044] entry_SYSENTER_compat+0x70/0x7f [ 47.669963] [ 47.669963] other info that might help us debug this: [ 47.669963] [ 47.678096] Possible unsafe locking scenario: [ 47.678096] [ 47.684139] CPU0 CPU1 [ 47.688883] ---- ---- [ 47.693534] lock(&pipe->mutex/1); [ 47.697154] lock(&sig->cred_guard_mutex); [ 47.703982] lock(&pipe->mutex/1); [ 47.710116] lock(&sig->cred_guard_mutex); [ 47.714426] [ 47.714426] *** DEADLOCK *** [ 47.714426] [ 47.720473] 2 locks held by syz-executor638/7846: [ 47.725300] #0: 000000009bc454d3 (sb_writers#6){.+.+}, at: do_splice+0xceb/0x1330 [ 47.733028] #1: 000000002040eaf3 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 [ 47.740663] [ 47.740663] stack backtrace: [ 47.745154] CPU: 0 PID: 7846 Comm: syz-executor638 Not tainted 5.0.0-rc7+ #80 [ 47.752416] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 47.761764] Call Trace: [ 47.764359] dump_stack+0x172/0x1f0 [ 47.767987] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 47.773347] __lock_acquire+0x2f00/0x4700 [ 47.777490] ? trace_hardirqs_on+0x67/0x230 [ 47.781817] ? kasan_check_read+0x11/0x20 [ 47.785969] ? mark_held_locks+0x100/0x100 [ 47.790198] ? __kmalloc_track_caller+0x158/0x740 [ 47.795042] ? memdup_user+0x26/0xb0 [ 47.798758] ? proc_pid_attr_write+0x196/0x530 [ 47.803337] ? __vfs_write+0x116/0x8e0 [ 47.807215] ? __kernel_write+0x110/0x3b0 [ 47.811358] ? write_pipe_buf+0x15d/0x1f0 [ 47.815500] ? __splice_from_pipe+0x39a/0x7e0 [ 47.819992] ? __lock_is_held+0xb6/0x140 [ 47.824056] ? proc_pid_attr_write+0x1fa/0x530 [ 47.828646] lock_acquire+0x16f/0x3f0 [ 47.832444] ? proc_pid_attr_write+0x1fa/0x530 [ 47.837027] ? proc_pid_attr_write+0x1fa/0x530 [ 47.841611] __mutex_lock+0xf7/0x1310 [ 47.845409] ? proc_pid_attr_write+0x1fa/0x530 [ 47.849992] ? proc_pid_attr_write+0x1fa/0x530 [ 47.854579] ? check_preemption_disabled+0x48/0x290 [ 47.859598] ? mutex_trylock+0x1e0/0x1e0 [ 47.863666] ? rcu_lockdep_current_cpu_online+0xe3/0x130 [ 47.869117] ? check_stack_object+0x114/0x160 [ 47.873610] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 47.879144] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 47.884685] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 47.890220] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 47.895784] ? _copy_from_user+0xdd/0x150 [ 47.899952] mutex_lock_interruptible_nested+0x16/0x20 [ 47.905235] ? mutex_lock_interruptible_nested+0x16/0x20 [ 47.910689] proc_pid_attr_write+0x1fa/0x530 [ 47.915112] __vfs_write+0x116/0x8e0 [ 47.918841] ? proc_loginuid_write+0x4d0/0x4d0 [ 47.923431] ? kernel_read+0x120/0x120 [ 47.927324] ? lock_pi_update_atomic+0x120/0x120 [ 47.932093] ? __lock_is_held+0xb6/0x140 [ 47.936150] ? lock_acquire+0x16f/0x3f0 [ 47.940129] __kernel_write+0x110/0x3b0 [ 47.944109] write_pipe_buf+0x15d/0x1f0 [ 47.948090] ? do_splice_direct+0x2a0/0x2a0 [ 47.952412] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 47.957952] ? splice_from_pipe_next.part.0+0x255/0x2f0 [ 47.963325] __splice_from_pipe+0x39a/0x7e0 [ 47.967647] ? do_splice_direct+0x2a0/0x2a0 [ 47.971976] ? do_splice_direct+0x2a0/0x2a0 [ 47.976294] splice_from_pipe+0x108/0x170 [ 47.980444] ? splice_shrink_spd+0xd0/0xd0 [ 47.984673] ? __lock_is_held+0xb6/0x140 [ 47.988738] ? rcu_lockdep_current_cpu_online+0xe3/0x130 [ 47.994192] default_file_splice_write+0x3c/0x90 [ 47.998944] ? generic_splice_sendpage+0x50/0x50 [ 48.003697] do_splice+0x644/0x1330 [ 48.007343] ? iterate_fd+0x360/0x360 [ 48.011169] ? opipe_prep.part.0+0x2d0/0x2d0 [ 48.015576] ? __fget_light+0x1a9/0x230 [ 48.019552] __ia32_sys_splice+0x2c4/0x330 [ 48.023794] do_fast_syscall_32+0x281/0xc98 [ 48.028129] entry_SYSENTER_compat+0x70/0x7f [ 48.032535] RIP: 0023:0xf7ff3869 [ 48.035899] Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 [ 48.054814] RSP: 002b:00000000f7fad1ec EFLAGS: 00000292 ORIG_RAX: 0000000000000139 [ 48.062525] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000 [ 48.069795] RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 [ 48.077090] RBP: 0000000000000009 R08: 0000000000000000 R09: 0000000000000000 [ 48.084365] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 48.091637] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000