[ 41.953691] audit: type=1800 audit(1546421357.407:25): pid=7828 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 41.985642] audit: type=1800 audit(1546421357.407:26): pid=7828 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 42.023493] audit: type=1800 audit(1546421357.417:27): pid=7828 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. [....] startpar: service(s) returned failure: ssh ...[?25l[?1c7[FAIL8[?25h[?0c failed! Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 46.899727] sshd (7986) used greatest stack depth: 19848 bytes left Warning: Permanently added '10.128.0.44' (ECDSA) to the list of known hosts. executing program [ 53.526460] [ 53.528113] ====================================================== [ 53.534404] WARNING: possible circular locking dependency detected [ 53.540698] 4.20.0-next-20190102 #2 Not tainted [ 53.545339] ------------------------------------------------------ [ 53.551632] syz-executor888/8002 is trying to acquire lock: [ 53.557317] 0000000075e418a6 (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 53.564668] [ 53.564668] but task is already holding lock: [ 53.570624] 0000000097858277 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x26d0 [ 53.579972] [ 53.579972] which lock already depends on the new lock. [ 53.579972] [ 53.588270] [ 53.588270] the existing dependency chain (in reverse order) is: [ 53.595871] [ 53.595871] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 53.602181] __mutex_lock+0x12f/0x1670 [ 53.606570] mutex_lock_interruptible_nested+0x16/0x20 [ 53.612352] proc_pid_attr_write+0x1fa/0x530 [ 53.617284] __vfs_write+0x116/0xb40 [ 53.621514] __kernel_write+0x110/0x3b0 [ 53.626001] write_pipe_buf+0x180/0x240 [ 53.630487] __splice_from_pipe+0x39a/0x7e0 [ 53.635308] splice_from_pipe+0x1ea/0x310 [ 53.639958] default_file_splice_write+0x3c/0x90 [ 53.645212] do_splice+0x64b/0x1410 [ 53.649344] __x64_sys_splice+0x2c6/0x330 [ 53.653998] do_syscall_64+0x1a3/0x800 [ 53.658395] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.664079] [ 53.664079] -> #0 (&pipe->mutex/1){+.+.}: [ 53.669697] lock_acquire+0x1db/0x570 [ 53.674006] __mutex_lock+0x12f/0x1670 [ 53.678392] mutex_lock_nested+0x16/0x20 [ 53.682958] fifo_open+0x159/0xb00 [ 53.686999] do_dentry_open+0x495/0x1230 [ 53.691559] vfs_open+0xa0/0xd0 [ 53.695357] path_openat+0x144f/0x5660 [ 53.699749] do_filp_open+0x26f/0x370 [ 53.704052] do_open_execat+0x207/0x8e0 [ 53.708542] __do_execve_file.isra.0+0x1939/0x26d0 [ 53.713973] __x64_sys_execve+0x8f/0xc0 [ 53.718449] do_syscall_64+0x1a3/0x800 [ 53.722837] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.728523] [ 53.728523] other info that might help us debug this: [ 53.728523] [ 53.736655] Possible unsafe locking scenario: [ 53.736655] [ 53.742686] CPU0 CPU1 [ 53.747325] ---- ---- [ 53.751964] lock(&sig->cred_guard_mutex); [ 53.756273] lock(&pipe->mutex/1); [ 53.762397] lock(&sig->cred_guard_mutex); [ 53.769230] lock(&pipe->mutex/1); [ 53.772863] [ 53.772863] *** DEADLOCK *** [ 53.772863] [ 53.778900] 1 lock held by syz-executor888/8002: [ 53.783632] #0: 0000000097858277 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x26d0 [ 53.793432] [ 53.793432] stack backtrace: [ 53.797906] CPU: 0 PID: 8002 Comm: syz-executor888 Not tainted 4.20.0-next-20190102 #2 [ 53.805936] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 53.815273] Call Trace: [ 53.817845] dump_stack+0x1db/0x2d0 [ 53.821454] ? dump_stack_print_info.cold+0x20/0x20 [ 53.826452] ? print_stack_trace+0x77/0xb0 [ 53.830669] ? vprintk_func+0x86/0x189 [ 53.834539] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 53.839887] __lock_acquire+0x2fed/0x4a10 [ 53.844019] ? is_bpf_text_address+0xac/0x170 [ 53.848502] ? mark_held_locks+0x100/0x100 [ 53.852719] ? mark_held_locks+0xb1/0x100 [ 53.856847] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 53.861931] ? lockdep_hardirqs_on+0x415/0x5d0 [ 53.866513] ? depot_save_stack+0x1de/0x460 [ 53.870819] ? trace_hardirqs_off_caller+0x300/0x300 [ 53.875901] ? do_raw_spin_trylock+0x270/0x270 [ 53.880463] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.885370] ? print_usage_bug+0xd0/0xd0 [ 53.889414] ? __lock_is_held+0xb6/0x140 [ 53.893455] lock_acquire+0x1db/0x570 [ 53.897234] ? fifo_open+0x159/0xb00 [ 53.900939] ? ___might_sleep+0x1e7/0x310 [ 53.905066] ? lock_release+0xc40/0xc40 [ 53.909020] ? fifo_open+0x159/0xb00 [ 53.912724] ? fifo_open+0x159/0xb00 [ 53.916420] __mutex_lock+0x12f/0x1670 [ 53.920287] ? fifo_open+0x159/0xb00 [ 53.923979] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.929496] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.935010] ? fifo_open+0x159/0xb00 [ 53.938705] ? lockdep_init_map+0x10c/0x5b0 [ 53.943006] ? mutex_trylock+0x2d0/0x2d0 [ 53.947046] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.951959] ? __mutex_init+0x1f6/0x2a0 [ 53.955914] ? psi_task_change.cold+0x1ec/0x1ec [ 53.960566] ? fifo_open+0x2b5/0xb00 [ 53.964267] ? find_held_lock+0x35/0x120 [ 53.968310] ? fifo_open+0x2b5/0xb00 [ 53.972025] ? lock_acquire+0x1db/0x570 [ 53.975983] ? kasan_check_read+0x11/0x20 [ 53.980113] ? do_raw_spin_unlock+0xa0/0x330 [ 53.984504] ? do_raw_spin_trylock+0x270/0x270 [ 53.989081] mutex_lock_nested+0x16/0x20 [ 53.993130] ? mutex_lock_nested+0x16/0x20 [ 53.997344] fifo_open+0x159/0xb00 [ 54.000868] do_dentry_open+0x495/0x1230 [ 54.004908] ? do_raw_spin_unlock+0xa0/0x330 [ 54.009304] ? pipe_release+0x280/0x280 [ 54.013268] ? chown_common+0x740/0x740 [ 54.017221] ? security_inode_permission+0xd5/0x110 [ 54.022225] ? inode_permission+0xb4/0x570 [ 54.026445] vfs_open+0xa0/0xd0 [ 54.029709] path_openat+0x144f/0x5660 [ 54.033579] ? is_bpf_text_address+0xd3/0x170 [ 54.038058] ? path_lookupat.isra.0+0xba0/0xba0 [ 54.042711] ? __lock_acquire+0x572/0x4a10 [ 54.046926] ? kmem_cache_alloc+0x12d/0x710 [ 54.051232] ? __do_execve_file.isra.0+0x47a/0x26d0 [ 54.056250] ? __x64_sys_execve+0x8f/0xc0 [ 54.060383] ? do_syscall_64+0x1a3/0x800 [ 54.064427] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 54.069773] ? add_lock_to_list.isra.0+0x450/0x450 [ 54.074696] do_filp_open+0x26f/0x370 [ 54.078476] ? may_open_dev+0x100/0x100 [ 54.082431] ? refcount_dec_and_mutex_lock+0x90/0x90 [ 54.087517] ? prepare_creds+0xa4/0x4e0 [ 54.091472] ? add_lock_to_list.isra.0+0x450/0x450 [ 54.096379] ? add_lock_to_list.isra.0+0x450/0x450 [ 54.101289] ? __do_execve_file.isra.0+0x901/0x26d0 [ 54.106297] do_open_execat+0x207/0x8e0 [ 54.110265] ? unregister_binfmt+0x2b0/0x2b0 [ 54.114658] ? kasan_check_read+0x11/0x20 [ 54.118787] ? do_raw_spin_trylock+0x270/0x270 [ 54.123365] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 54.128885] __do_execve_file.isra.0+0x1939/0x26d0 [ 54.133799] ? copy_strings_kernel+0x110/0x110 [ 54.138364] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 54.143881] ? strncpy_from_user+0x317/0x440 [ 54.148277] ? digsig_verify.cold+0x32/0x32 [ 54.152579] ? kmem_cache_alloc+0x341/0x710 [ 54.156884] ? do_syscall_64+0x8c/0x800 [ 54.160841] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 54.166365] ? getname_flags+0x277/0x5b0 [ 54.170406] ? trace_hardirqs_off_caller+0x300/0x300 [ 54.175492] __x64_sys_execve+0x8f/0xc0 [ 54.179455] do_syscall_64+0x1a3/0x800 [ 54.183322] ? syscall_return_slowpath+0x5f0/0x5f0 [ 54.188231] ? prepare_exit_to_usermode+0x3b0/0x3b0 [ 54.193247] ? __switch_to_asm+0x34/0x70 [ 54.197294] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 54.202127] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 54.207304] RIP: 0033:0x445729 [ 54.210480] 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 [