[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 39.269562] audit: type=1800 audit(1547472190.653:25): pid=7825 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 39.306593] audit: type=1800 audit(1547472190.653:26): pid=7825 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 39.336774] audit: type=1800 audit(1547472190.653:27): pid=7825 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 '10.128.0.246' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 50.296453] [ 50.298101] ====================================================== [ 50.304395] WARNING: possible circular locking dependency detected [ 50.310690] 5.0.0-rc2 #25 Not tainted [ 50.314461] ------------------------------------------------------ [ 50.320751] syz-executor058/7980 is trying to acquire lock: [ 50.326440] 00000000e285fa6c (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 50.333799] [ 50.333799] but task is already holding lock: [ 50.339739] 00000000277da8c6 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 50.349086] [ 50.349086] which lock already depends on the new lock. [ 50.349086] [ 50.357383] [ 50.357383] the existing dependency chain (in reverse order) is: [ 50.364990] [ 50.364990] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 50.371324] __mutex_lock+0x12f/0x1670 [ 50.375712] mutex_lock_interruptible_nested+0x16/0x20 [ 50.381486] proc_pid_attr_write+0x1fa/0x530 [ 50.386397] __vfs_write+0x116/0xb40 [ 50.390611] __kernel_write+0x110/0x3b0 [ 50.395086] write_pipe_buf+0x180/0x240 [ 50.399559] __splice_from_pipe+0x39a/0x7e0 [ 50.404383] splice_from_pipe+0x1ea/0x310 [ 50.409039] default_file_splice_write+0x3c/0x90 [ 50.414296] do_splice+0x64b/0x1410 [ 50.418422] __ia32_sys_splice+0x2c4/0x330 [ 50.423160] do_fast_syscall_32+0x333/0xf98 [ 50.427999] entry_SYSENTER_compat+0x70/0x7f [ 50.432907] [ 50.432907] -> #0 (&pipe->mutex/1){+.+.}: [ 50.438566] lock_acquire+0x1db/0x570 [ 50.442870] __mutex_lock+0x12f/0x1670 [ 50.447270] mutex_lock_nested+0x16/0x20 [ 50.451845] fifo_open+0x159/0xb00 [ 50.455887] do_dentry_open+0x48a/0x1210 [ 50.460450] vfs_open+0xa0/0xd0 [ 50.464230] path_openat+0x144f/0x5650 [ 50.468613] do_filp_open+0x26f/0x370 [ 50.472945] do_open_execat+0x20e/0x930 [ 50.477423] __do_execve_file.isra.0+0x1966/0x2700 [ 50.482852] __ia32_compat_sys_execve+0x94/0xc0 [ 50.488020] do_fast_syscall_32+0x333/0xf98 [ 50.492845] entry_SYSENTER_compat+0x70/0x7f [ 50.497746] [ 50.497746] other info that might help us debug this: [ 50.497746] [ 50.505874] Possible unsafe locking scenario: [ 50.505874] [ 50.511903] CPU0 CPU1 [ 50.516543] ---- ---- [ 50.521181] lock(&sig->cred_guard_mutex); [ 50.525499] lock(&pipe->mutex/1); [ 50.531621] lock(&sig->cred_guard_mutex); [ 50.538432] lock(&pipe->mutex/1); [ 50.542038] [ 50.542038] *** DEADLOCK *** [ 50.542038] [ 50.548072] 1 lock held by syz-executor058/7980: [ 50.552801] #0: 00000000277da8c6 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 50.562580] [ 50.562580] stack backtrace: [ 50.567055] CPU: 0 PID: 7980 Comm: syz-executor058 Not tainted 5.0.0-rc2 #25 [ 50.574213] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 50.583544] Call Trace: [ 50.586112] dump_stack+0x1db/0x2d0 [ 50.589717] ? dump_stack_print_info.cold+0x20/0x20 [ 50.594714] ? print_stack_trace+0x77/0xb0 [ 50.598933] ? vprintk_func+0x86/0x189 [ 50.602807] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 50.608149] __lock_acquire+0x3014/0x4a30 [ 50.612288] ? mark_held_locks+0x100/0x100 [ 50.616536] ? mark_held_locks+0xb1/0x100 [ 50.620663] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 50.625756] ? lockdep_hardirqs_on+0x415/0x5d0 [ 50.630337] ? trace_hardirqs_off_caller+0x300/0x300 [ 50.635420] ? do_raw_spin_trylock+0x270/0x270 [ 50.639980] ? add_lock_to_list.isra.0+0x450/0x450 [ 50.644890] ? print_usage_bug+0xd0/0xd0 [ 50.648937] ? __lock_is_held+0xb6/0x140 [ 50.652985] lock_acquire+0x1db/0x570 [ 50.656766] ? fifo_open+0x159/0xb00 [ 50.660458] ? ___might_sleep+0x1e7/0x310 [ 50.664587] ? lock_release+0xc40/0xc40 [ 50.668543] ? fifo_open+0x159/0xb00 [ 50.672240] ? fifo_open+0x159/0xb00 [ 50.675953] __mutex_lock+0x12f/0x1670 [ 50.679822] ? fifo_open+0x159/0xb00 [ 50.683511] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 50.689023] ? fifo_open+0x159/0xb00 [ 50.692719] ? check_preemption_disabled+0x48/0x290 [ 50.697716] ? lockdep_init_map+0x10c/0x5b0 [ 50.702014] ? mutex_trylock+0x2d0/0x2d0 [ 50.706053] ? add_lock_to_list.isra.0+0x450/0x450 [ 50.710970] ? __mutex_init+0x1f6/0x2a0 [ 50.714933] ? psi_task_change.cold+0x1ec/0x1ec [ 50.719584] ? fifo_open+0x2b5/0xb00 [ 50.723276] ? find_held_lock+0x35/0x120 [ 50.727317] ? fifo_open+0x2b5/0xb00 [ 50.731013] ? lock_acquire+0x1db/0x570 [ 50.734968] ? kasan_check_read+0x11/0x20 [ 50.739094] ? do_raw_spin_unlock+0xa0/0x330 [ 50.743487] ? do_raw_spin_trylock+0x270/0x270 [ 50.748049] mutex_lock_nested+0x16/0x20 [ 50.752096] ? _raw_spin_unlock+0x2d/0x50 [ 50.756226] ? mutex_lock_nested+0x16/0x20 [ 50.760443] fifo_open+0x159/0xb00 [ 50.763965] do_dentry_open+0x48a/0x1210 [ 50.768010] ? pipe_release+0x280/0x280 [ 50.771978] ? chown_common+0x740/0x740 [ 50.775953] ? security_inode_permission+0xd5/0x110 [ 50.780960] ? inode_permission+0xb4/0x570 [ 50.785222] vfs_open+0xa0/0xd0 [ 50.788492] path_openat+0x144f/0x5650 [ 50.792365] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 50.797539] ? lockdep_hardirqs_on+0x415/0x5d0 [ 50.802102] ? trace_hardirqs_on+0xbd/0x310 [ 50.806406] ? path_lookupat.isra.0+0xba0/0xba0 [ 50.811053] ? depot_save_stack+0x1de/0x460 [ 50.815353] ? __lock_acquire+0x572/0x4a30 [ 50.819565] ? kmem_cache_alloc+0x12d/0x710 [ 50.823866] ? __do_execve_file.isra.0+0x47a/0x2700 [ 50.828858] ? __ia32_compat_sys_execve+0x94/0xc0 [ 50.833679] ? do_fast_syscall_32+0x333/0xf98 [ 50.838151] ? entry_SYSENTER_compat+0x70/0x7f [ 50.842710] ? add_lock_to_list.isra.0+0x450/0x450 [ 50.847618] do_filp_open+0x26f/0x370 [ 50.851394] ? may_open_dev+0x100/0x100 [ 50.855347] ? refcount_add_not_zero_checked+0x330/0x330 [ 50.860781] ? prepare_creds+0xa4/0x4e0 [ 50.864879] ? add_lock_to_list.isra.0+0x450/0x450 [ 50.869785] ? add_lock_to_list.isra.0+0x450/0x450 [ 50.874694] ? __do_execve_file.isra.0+0x901/0x2700 [ 50.879686] do_open_execat+0x20e/0x930 [ 50.883643] ? unregister_binfmt+0x2b0/0x2b0 [ 50.888033] ? kasan_check_read+0x11/0x20 [ 50.892160] ? do_raw_spin_trylock+0x270/0x270 [ 50.896725] ? __phys_addr_symbol+0x30/0x70 [ 50.901028] __do_execve_file.isra.0+0x1966/0x2700 [ 50.905953] ? copy_strings_kernel+0x110/0x110 [ 50.910518] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 50.916042] ? strncpy_from_user+0x3aa/0x4e0 [ 50.920433] ? digsig_verify.cold+0x32/0x32 [ 50.924738] ? kmem_cache_alloc+0x341/0x710 [ 50.929041] ? do_fast_syscall_32+0x13b/0xf98 [ 50.933516] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 50.939029] ? getname_flags+0x277/0x5b0 [ 50.943069] ? trace_hardirqs_off_caller+0x300/0x300 [ 50.948152] __ia32_compat_sys_execve+0x94/0xc0 [ 50.952803] do_fast_syscall_32+0x333/0xf98 [ 50.957103] ? do_int80_syscall_32+0x880/0x880 [ 50.961668] ? trace_hardirqs_off+0x310/0x310 [ 50.966143] ? syscall_return_slowpath+0x3b0/0x5f0 [ 50.971052] ? prepare_exit_to_usermode+0x3b0/0x3b0 [ 50.976062] ? __switch_to_asm+0x34/0x70 [ 50.980108] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 50.984945] entry_SYSENTER_compat+0x70/0x7f [ 50.989331] RIP: 0023:0xf7f23869 [ 50.992676] 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 [ 51.011555] RSP: 002b:00000000f7efe1fc EFLAGS: 00000246 ORIG_RAX: 000000000000000b [ 51.019240] RAX: ffffffffffffffda RBX: 0000000020000040 RCX: 0000000000000000 [ 51.026488] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 51.033738] RBP: 00000000003d0f00 R08: 0000000000000000 R09: 0000000000000000 [ 51.040996] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 51.048252] R13: