[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 40.461241] audit: type=1800 audit(1546435615.266:25): pid=7924 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 40.499189] audit: type=1800 audit(1546435615.266:26): pid=7924 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 40.539560] audit: type=1800 audit(1546435615.266:27): pid=7924 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 '10.128.0.67' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 52.625912] [ 52.627560] ====================================================== [ 52.633858] WARNING: possible circular locking dependency detected [ 52.640152] 4.20.0-next-20190102 #2 Not tainted [ 52.644792] ------------------------------------------------------ [ 52.651084] syz-executor146/8075 is trying to acquire lock: [ 52.656768] 00000000a15e08ef (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 52.664117] [ 52.664117] but task is already holding lock: [ 52.670062] 000000009da69b22 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x26d0 [ 52.679404] [ 52.679404] which lock already depends on the new lock. [ 52.679404] [ 52.687691] [ 52.687691] the existing dependency chain (in reverse order) is: [ 52.695286] [ 52.695286] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 52.701614] __mutex_lock+0x12f/0x1670 [ 52.706000] mutex_lock_interruptible_nested+0x16/0x20 [ 52.711788] proc_pid_attr_write+0x1fa/0x530 [ 52.716696] __vfs_write+0x116/0xb40 [ 52.720912] __kernel_write+0x110/0x3b0 [ 52.725384] write_pipe_buf+0x180/0x240 [ 52.729860] __splice_from_pipe+0x39a/0x7e0 [ 52.734682] splice_from_pipe+0x1ea/0x310 [ 52.739330] default_file_splice_write+0x3c/0x90 [ 52.744585] do_splice+0x64b/0x1410 [ 52.748711] __x64_sys_splice+0x2c6/0x330 [ 52.753364] do_syscall_64+0x1a3/0x800 [ 52.757749] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 52.763448] [ 52.763448] -> #0 (&pipe->mutex/1){+.+.}: [ 52.769063] lock_acquire+0x1db/0x570 [ 52.773364] __mutex_lock+0x12f/0x1670 [ 52.777749] mutex_lock_nested+0x16/0x20 [ 52.782313] fifo_open+0x159/0xb00 [ 52.786362] do_dentry_open+0x495/0x1230 [ 52.790924] vfs_open+0xa0/0xd0 [ 52.794703] path_openat+0x144f/0x5660 [ 52.799092] do_filp_open+0x26f/0x370 [ 52.803391] do_open_execat+0x207/0x8e0 [ 52.807875] __do_execve_file.isra.0+0x1939/0x26d0 [ 52.813309] __x64_sys_execve+0x8f/0xc0 [ 52.817787] do_syscall_64+0x1a3/0x800 [ 52.822186] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 52.827875] [ 52.827875] other info that might help us debug this: [ 52.827875] [ 52.835994] Possible unsafe locking scenario: [ 52.835994] [ 52.842024] CPU0 CPU1 [ 52.846666] ---- ---- [ 52.851320] lock(&sig->cred_guard_mutex); [ 52.855619] lock(&pipe->mutex/1); [ 52.861739] lock(&sig->cred_guard_mutex); [ 52.868553] lock(&pipe->mutex/1); [ 52.872170] [ 52.872170] *** DEADLOCK *** [ 52.872170] [ 52.878207] 1 lock held by syz-executor146/8075: [ 52.882935] #0: 000000009da69b22 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x26d0 [ 52.892712] [ 52.892712] stack backtrace: [ 52.897188] CPU: 1 PID: 8075 Comm: syz-executor146 Not tainted 4.20.0-next-20190102 #2 [ 52.905218] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 52.914549] Call Trace: [ 52.917129] dump_stack+0x1db/0x2d0 [ 52.920753] ? dump_stack_print_info.cold+0x20/0x20 [ 52.925780] ? print_stack_trace+0x77/0xb0 [ 52.930000] ? vprintk_func+0x86/0x189 [ 52.933868] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 52.939214] __lock_acquire+0x2fed/0x4a10 [ 52.943360] ? is_bpf_text_address+0xac/0x170 [ 52.947864] ? mark_held_locks+0x100/0x100 [ 52.952100] ? mark_held_locks+0xb1/0x100 [ 52.956229] ? _raw_spin_unlock_irqrestore+0x6b/0xe0 [ 52.961311] ? lockdep_hardirqs_on+0x415/0x5d0 [ 52.965877] ? depot_save_stack+0x1de/0x460 [ 52.970198] ? trace_hardirqs_off_caller+0x300/0x300 [ 52.975280] ? do_raw_spin_trylock+0x270/0x270 [ 52.979856] ? add_lock_to_list.isra.0+0x450/0x450 [ 52.984766] ? print_usage_bug+0xd0/0xd0 [ 52.988807] ? __lock_is_held+0xb6/0x140 [ 52.992858] lock_acquire+0x1db/0x570 [ 52.996640] ? fifo_open+0x159/0xb00 [ 53.000333] ? ___might_sleep+0x1e7/0x310 [ 53.004464] ? lock_release+0xc40/0xc40 [ 53.008420] ? fifo_open+0x159/0xb00 [ 53.012115] ? fifo_open+0x159/0xb00 [ 53.015808] __mutex_lock+0x12f/0x1670 [ 53.019680] ? fifo_open+0x159/0xb00 [ 53.023378] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.028895] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.034410] ? fifo_open+0x159/0xb00 [ 53.038106] ? lockdep_init_map+0x10c/0x5b0 [ 53.042407] ? mutex_trylock+0x2d0/0x2d0 [ 53.046447] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.051360] ? __mutex_init+0x1f6/0x2a0 [ 53.055328] ? psi_task_change.cold+0x1ec/0x1ec [ 53.059983] ? fifo_open+0x2b5/0xb00 [ 53.063675] ? find_held_lock+0x35/0x120 [ 53.067716] ? fifo_open+0x2b5/0xb00 [ 53.071425] ? lock_acquire+0x1db/0x570 [ 53.075383] ? kasan_check_read+0x11/0x20 [ 53.079511] ? do_raw_spin_unlock+0xa0/0x330 [ 53.083901] ? do_raw_spin_trylock+0x270/0x270 [ 53.088465] mutex_lock_nested+0x16/0x20 [ 53.092505] ? mutex_lock_nested+0x16/0x20 [ 53.096718] fifo_open+0x159/0xb00 [ 53.100239] do_dentry_open+0x495/0x1230 [ 53.104287] ? do_raw_spin_unlock+0xa0/0x330 [ 53.108674] ? pipe_release+0x280/0x280 [ 53.112642] ? chown_common+0x740/0x740 [ 53.116595] ? security_inode_permission+0xd5/0x110 [ 53.121592] ? inode_permission+0xb4/0x570 [ 53.125825] vfs_open+0xa0/0xd0 [ 53.129089] path_openat+0x144f/0x5660 [ 53.132976] ? is_bpf_text_address+0xd3/0x170 [ 53.137498] ? path_lookupat.isra.0+0xba0/0xba0 [ 53.142147] ? __lock_acquire+0x572/0x4a10 [ 53.146367] ? kmem_cache_alloc+0x12d/0x710 [ 53.150670] ? __do_execve_file.isra.0+0x47a/0x26d0 [ 53.155663] ? __x64_sys_execve+0x8f/0xc0 [ 53.159789] ? do_syscall_64+0x1a3/0x800 [ 53.163836] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.169180] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.174091] do_filp_open+0x26f/0x370 [ 53.177892] ? may_open_dev+0x100/0x100 [ 53.181863] ? refcount_dec_and_mutex_lock+0x90/0x90 [ 53.186948] ? prepare_creds+0xa4/0x4e0 [ 53.190921] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.195835] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.200752] ? __do_execve_file.isra.0+0x901/0x26d0 [ 53.205749] do_open_execat+0x207/0x8e0 [ 53.209705] ? unregister_binfmt+0x2b0/0x2b0 [ 53.214096] ? kasan_check_read+0x11/0x20 [ 53.218224] ? do_raw_spin_trylock+0x270/0x270 [ 53.222785] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 53.228324] __do_execve_file.isra.0+0x1939/0x26d0 [ 53.233240] ? rcu_pm_notify+0xd0/0xd0 [ 53.237106] ? copy_strings_kernel+0x110/0x110 [ 53.241681] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 53.247198] ? strncpy_from_user+0x317/0x440 [ 53.251587] ? digsig_verify.cold+0x32/0x32 [ 53.255886] ? kmem_cache_alloc+0x341/0x710 [ 53.260189] ? do_syscall_64+0x8c/0x800 [ 53.264160] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.269679] ? getname_flags+0x277/0x5b0 [ 53.273721] ? trace_hardirqs_off_caller+0x300/0x300 [ 53.278804] __x64_sys_execve+0x8f/0xc0 [ 53.282766] do_syscall_64+0x1a3/0x800 [ 53.286632] ? syscall_return_slowpath+0x5f0/0x5f0 [ 53.291543] ? prepare_exit_to_usermode+0x232/0x3b0 [ 53.296539] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 53.301368] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.306558] RIP: 0033:0x440119 [ 53.309753] 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 [ 53.328635] RSP: 002b:00007ffde5d98a58 EFLAGS: 00000217 ORIG_RAX: 000000000000003b [ 53.336320] RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440119 [ 53.343570] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000340 [ 53.350819] RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 [ 53.358078] R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004019a0 [ 53.365326] R13: 0000000000401a30 R14: 0000000000000000 R15: 0000000000000000