[ 38.489752] audit: type=1800 audit(1550611228.114:25): pid=7707 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 38.525293] audit: type=1800 audit(1550611228.114:26): pid=7707 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 38.569124] audit: type=1800 audit(1550611228.114:27): pid=7707 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0 [ 38.592936] audit: type=1800 audit(1550611228.114:28): pid=7707 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. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.183' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 49.410753] [ 49.412398] ====================================================== [ 49.418694] WARNING: possible circular locking dependency detected [ 49.424994] 5.0.0-rc7+ #79 Not tainted [ 49.428866] ------------------------------------------------------ [ 49.435202] syz-executor078/7863 is trying to acquire lock: [ 49.440908] 00000000ce924167 (&sig->cred_guard_mutex){+.+.}, at: proc_pid_attr_write+0x1fa/0x530 [ 49.449828] [ 49.449828] but task is already holding lock: [ 49.455787] 000000001577bd72 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 [ 49.462994] [ 49.462994] which lock already depends on the new lock. [ 49.462994] [ 49.471303] [ 49.471303] the existing dependency chain (in reverse order) is: [ 49.478908] [ 49.478908] -> #1 (&pipe->mutex/1){+.+.}: [ 49.484531] __mutex_lock+0xf7/0x1310 [ 49.488838] mutex_lock_nested+0x16/0x20 [ 49.493406] fifo_open+0x159/0xb00 [ 49.497451] do_dentry_open+0x47d/0x1130 [ 49.502012] vfs_open+0xa0/0xd0 [ 49.505796] path_openat+0x10d7/0x4690 [ 49.510199] do_filp_open+0x1a1/0x280 [ 49.514501] do_open_execat+0x13b/0x6d0 [ 49.518977] __do_execve_file.isra.0+0x178d/0x23f0 [ 49.524407] __x64_sys_execve+0x8f/0xc0 [ 49.528885] do_syscall_64+0x103/0x610 [ 49.533276] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 49.538961] [ 49.538961] -> #0 (&sig->cred_guard_mutex){+.+.}: [ 49.545269] lock_acquire+0x16f/0x3f0 [ 49.549575] __mutex_lock+0xf7/0x1310 [ 49.553887] mutex_lock_interruptible_nested+0x16/0x20 [ 49.559672] proc_pid_attr_write+0x1fa/0x530 [ 49.564593] __vfs_write+0x116/0x8e0 [ 49.568828] __kernel_write+0x110/0x3b0 [ 49.573321] write_pipe_buf+0x15d/0x1f0 [ 49.577820] __splice_from_pipe+0x39a/0x7e0 [ 49.582659] splice_from_pipe+0x108/0x170 [ 49.587323] default_file_splice_write+0x3c/0x90 [ 49.592600] do_splice+0x644/0x1330 [ 49.596744] __x64_sys_splice+0x2c6/0x330 [ 49.601414] do_syscall_64+0x103/0x610 [ 49.605828] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 49.611530] [ 49.611530] other info that might help us debug this: [ 49.611530] [ 49.619662] Possible unsafe locking scenario: [ 49.619662] [ 49.625709] CPU0 CPU1 [ 49.630370] ---- ---- [ 49.635028] lock(&pipe->mutex/1); [ 49.638654] lock(&sig->cred_guard_mutex); [ 49.645490] lock(&pipe->mutex/1); [ 49.651653] lock(&sig->cred_guard_mutex); [ 49.655977] [ 49.655977] *** DEADLOCK *** [ 49.655977] [ 49.662037] 2 locks held by syz-executor078/7863: [ 49.666874] #0: 00000000f2e0ce39 (sb_writers#6){.+.+}, at: do_splice+0xceb/0x1330 [ 49.674605] #1: 000000001577bd72 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 [ 49.682251] [ 49.682251] stack backtrace: [ 49.686798] CPU: 1 PID: 7863 Comm: syz-executor078 Not tainted 5.0.0-rc7+ #79 [ 49.694077] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 49.703430] Call Trace: [ 49.706024] dump_stack+0x172/0x1f0 [ 49.709742] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 49.715111] __lock_acquire+0x2f00/0x4700 [ 49.719264] ? trace_hardirqs_on+0x67/0x230 [ 49.723590] ? kasan_check_read+0x11/0x20 [ 49.727744] ? mark_held_locks+0x100/0x100 [ 49.731984] ? __kmalloc_track_caller+0x158/0x740 [ 49.736832] ? memdup_user+0x26/0xb0 [ 49.740550] ? proc_pid_attr_write+0x196/0x530 [ 49.745132] ? __vfs_write+0x116/0x8e0 [ 49.749017] ? __kernel_write+0x110/0x3b0 [ 49.753177] ? write_pipe_buf+0x15d/0x1f0 [ 49.757332] ? __splice_from_pipe+0x39a/0x7e0 [ 49.761843] ? __lock_is_held+0xb6/0x140 [ 49.765911] ? proc_pid_attr_write+0x1fa/0x530 [ 49.770504] lock_acquire+0x16f/0x3f0 [ 49.774322] ? proc_pid_attr_write+0x1fa/0x530 [ 49.778931] ? proc_pid_attr_write+0x1fa/0x530 [ 49.783519] __mutex_lock+0xf7/0x1310 [ 49.787325] ? proc_pid_attr_write+0x1fa/0x530 [ 49.791911] ? proc_pid_attr_write+0x1fa/0x530 [ 49.796496] ? check_preemption_disabled+0x48/0x290 [ 49.801518] ? mutex_trylock+0x1e0/0x1e0 [ 49.805584] ? rcu_lockdep_current_cpu_online+0xe3/0x130 [ 49.811047] ? check_stack_object+0x114/0x160 [ 49.815549] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 49.821088] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 49.826637] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 49.832665] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 49.838213] ? _copy_from_user+0xdd/0x150 [ 49.842369] mutex_lock_interruptible_nested+0x16/0x20 [ 49.847652] ? mutex_lock_interruptible_nested+0x16/0x20 [ 49.853108] proc_pid_attr_write+0x1fa/0x530 [ 49.857523] __vfs_write+0x116/0x8e0 [ 49.861240] ? proc_loginuid_write+0x4d0/0x4d0 [ 49.865839] ? kernel_read+0x120/0x120 [ 49.869732] ? lock_pi_update_atomic+0x120/0x120 [ 49.874499] ? __lock_is_held+0xb6/0x140 [ 49.878563] ? lock_acquire+0x16f/0x3f0 [ 49.882543] __kernel_write+0x110/0x3b0 [ 49.886522] write_pipe_buf+0x15d/0x1f0 [ 49.890498] ? do_splice_direct+0x2a0/0x2a0 [ 49.894829] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 49.900393] ? splice_from_pipe_next.part.0+0x255/0x2f0 [ 49.905769] __splice_from_pipe+0x39a/0x7e0 [ 49.910093] ? do_splice_direct+0x2a0/0x2a0 [ 49.914429] ? do_splice_direct+0x2a0/0x2a0 [ 49.918753] splice_from_pipe+0x108/0x170 [ 49.922908] ? splice_shrink_spd+0xd0/0xd0 [ 49.927143] ? __lock_is_held+0xb6/0x140 [ 49.931216] ? rcu_lockdep_current_cpu_online+0xe3/0x130 [ 49.936663] default_file_splice_write+0x3c/0x90 [ 49.941415] ? generic_splice_sendpage+0x50/0x50 [ 49.946165] do_splice+0x644/0x1330 [ 49.949811] ? iterate_fd+0x360/0x360 [ 49.953620] ? opipe_prep.part.0+0x2d0/0x2d0 [ 49.958030] ? __fget_light+0x1a9/0x230 [ 49.962001] __x64_sys_splice+0x2c6/0x330 [ 49.966155] do_syscall_64+0x103/0x610 [ 49.970054] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 49.975244] RIP: 0033:0x445779 [ 49.978436] 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 [ 49.997345] RSP: 002b:00007fc8cda61da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 [ 50.005062] RAX: ffffffffffffffda RBX: 00000000006dac68 RCX: 0000000000445779 [ 50.012336] RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 [ 50.019628] RBP: 00000000006dac60 R08: 0000020000000003 R09: 0000000000000009 [ 50.026901] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac6c [ 50.034188] R13: 00007ffed72eae3f R14: 00007fc8cda629c0 R15: 20c49ba5e353f7cf