[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 40.772947][ T26] audit: type=1800 audit(1546994136.143:25): pid=7810 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 40.820523][ T26] audit: type=1800 audit(1546994136.143:26): pid=7810 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 40.855058][ T26] audit: type=1800 audit(1546994136.153:27): pid=7810 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 '10.128.10.56' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 52.768187][ T7964] [ 52.770554][ T7964] ====================================================== [ 52.777545][ T7964] WARNING: possible circular locking dependency detected [ 52.784536][ T7964] 5.0.0-rc1-next-20190108 #7 Not tainted [ 52.790138][ T7964] ------------------------------------------------------ [ 52.797145][ T7964] syz-executor800/7964 is trying to acquire lock: [ 52.803528][ T7964] 00000000e9d46351 (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 52.811577][ T7964] [ 52.811577][ T7964] but task is already holding lock: [ 52.818918][ T7964] 0000000045fb2139 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 52.829060][ T7964] [ 52.829060][ T7964] which lock already depends on the new lock. [ 52.829060][ T7964] [ 52.839450][ T7964] [ 52.839450][ T7964] the existing dependency chain (in reverse order) is: [ 52.848439][ T7964] [ 52.848439][ T7964] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 52.856144][ T7964] __mutex_lock+0x12f/0x1670 [ 52.861232][ T7964] mutex_lock_interruptible_nested+0x16/0x20 [ 52.867712][ T7964] proc_pid_attr_write+0x1fa/0x530 [ 52.873320][ T7964] __vfs_write+0x116/0xb40 [ 52.878233][ T7964] __kernel_write+0x110/0x3b0 [ 52.883409][ T7964] write_pipe_buf+0x180/0x240 [ 52.888582][ T7964] __splice_from_pipe+0x39a/0x7e0 [ 52.894102][ T7964] splice_from_pipe+0x1ea/0x310 [ 52.899468][ T7964] default_file_splice_write+0x3c/0x90 [ 52.905427][ T7964] do_splice+0x64b/0x1410 [ 52.910262][ T7964] __x64_sys_splice+0x2c6/0x330 [ 52.915610][ T7964] do_syscall_64+0x1a3/0x800 [ 52.920700][ T7964] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 52.927083][ T7964] [ 52.927083][ T7964] -> #0 (&pipe->mutex/1){+.+.}: [ 52.934108][ T7964] lock_acquire+0x1db/0x570 [ 52.939112][ T7964] __mutex_lock+0x12f/0x1670 [ 52.944199][ T7964] mutex_lock_nested+0x16/0x20 [ 52.949455][ T7964] fifo_open+0x159/0xb00 [ 52.954208][ T7964] do_dentry_open+0x495/0x1230 [ 52.959467][ T7964] vfs_open+0xa0/0xd0 [ 52.963946][ T7964] path_openat+0x144f/0x5660 [ 52.969043][ T7964] do_filp_open+0x26f/0x370 [ 52.974735][ T7964] do_open_execat+0x207/0x8e0 [ 52.979915][ T7964] __do_execve_file.isra.0+0x1966/0x2700 [ 52.986042][ T7964] __x64_sys_execve+0x8f/0xc0 [ 52.991303][ T7964] do_syscall_64+0x1a3/0x800 [ 52.996388][ T7964] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.002776][ T7964] [ 53.002776][ T7964] other info that might help us debug this: [ 53.002776][ T7964] [ 53.012974][ T7964] Possible unsafe locking scenario: [ 53.012974][ T7964] [ 53.020402][ T7964] CPU0 CPU1 [ 53.025737][ T7964] ---- ---- [ 53.031074][ T7964] lock(&sig->cred_guard_mutex); [ 53.036067][ T7964] lock(&pipe->mutex/1); [ 53.042883][ T7964] lock(&sig->cred_guard_mutex); [ 53.050391][ T7964] lock(&pipe->mutex/1); [ 53.054690][ T7964] [ 53.054690][ T7964] *** DEADLOCK *** [ 53.054690][ T7964] [ 53.062809][ T7964] 1 lock held by syz-executor800/7964: [ 53.068318][ T7964] #0: 0000000045fb2139 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 53.078795][ T7964] [ 53.078795][ T7964] stack backtrace: [ 53.084661][ T7964] CPU: 0 PID: 7964 Comm: syz-executor800 Not tainted 5.0.0-rc1-next-20190108 #7 [ 53.093645][ T7964] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 53.103685][ T7964] Call Trace: [ 53.106951][ T7964] dump_stack+0x1db/0x2d0 [ 53.111344][ T7964] ? dump_stack_print_info.cold+0x20/0x20 [ 53.117051][ T7964] ? print_stack_trace+0x77/0xb0 [ 53.121962][ T7964] ? vprintk_func+0x86/0x189 [ 53.126529][ T7964] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 53.132571][ T7964] __lock_acquire+0x2fed/0x4a10 [ 53.137415][ T7964] ? mark_held_locks+0x100/0x100 [ 53.142328][ T7964] ? lockdep_hardirqs_on+0x415/0x5d0 [ 53.147588][ T7964] ? trace_hardirqs_on+0xbd/0x310 [ 53.152588][ T7964] ? do_raw_spin_trylock+0x270/0x270 [ 53.157849][ T7964] ? unwind_get_return_address+0x61/0xa0 [ 53.163456][ T7964] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.169061][ T7964] ? print_usage_bug+0xd0/0xd0 [ 53.173801][ T7964] ? depot_save_stack+0x1de/0x460 [ 53.178798][ T7964] ? __lock_is_held+0xb6/0x140 [ 53.183534][ T7964] ? save_stack+0xa9/0xd0 [ 53.187835][ T7964] lock_acquire+0x1db/0x570 [ 53.192335][ T7964] ? fifo_open+0x159/0xb00 [ 53.196726][ T7964] ? ___might_sleep+0x1e7/0x310 [ 53.201549][ T7964] ? lock_release+0xc40/0xc40 [ 53.206213][ T7964] ? fifo_open+0x159/0xb00 [ 53.210605][ T7964] ? fifo_open+0x159/0xb00 [ 53.215002][ T7964] __mutex_lock+0x12f/0x1670 [ 53.219567][ T7964] ? fifo_open+0x159/0xb00 [ 53.223956][ T7964] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.230167][ T7964] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.236381][ T7964] ? fifo_open+0x159/0xb00 [ 53.240774][ T7964] ? lockdep_init_map+0x10c/0x5b0 [ 53.245788][ T7964] ? mutex_trylock+0x2d0/0x2d0 [ 53.250526][ T7964] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.256131][ T7964] ? __mutex_init+0x1f6/0x2a0 [ 53.260783][ T7964] ? psi_task_change.cold+0x1ec/0x1ec [ 53.266127][ T7964] ? fifo_open+0x2b5/0xb00 [ 53.270519][ T7964] ? find_held_lock+0x35/0x120 [ 53.275263][ T7964] ? fifo_open+0x2b5/0xb00 [ 53.279651][ T7964] ? lock_acquire+0x1db/0x570 [ 53.284305][ T7964] ? kasan_check_read+0x11/0x20 [ 53.289127][ T7964] ? do_raw_spin_unlock+0xa0/0x330 [ 53.294210][ T7964] ? do_raw_spin_trylock+0x270/0x270 [ 53.299486][ T7964] mutex_lock_nested+0x16/0x20 [ 53.304226][ T7964] ? mutex_lock_nested+0x16/0x20 [ 53.309136][ T7964] fifo_open+0x159/0xb00 [ 53.313358][ T7964] do_dentry_open+0x495/0x1230 [ 53.318102][ T7964] ? do_raw_spin_unlock+0xa0/0x330 [ 53.323189][ T7964] ? pipe_release+0x280/0x280 [ 53.327861][ T7964] ? chown_common+0x740/0x740 [ 53.332515][ T7964] ? security_inode_permission+0xd5/0x110 [ 53.338208][ T7964] ? inode_permission+0xb4/0x570 [ 53.343120][ T7964] vfs_open+0xa0/0xd0 [ 53.347075][ T7964] path_openat+0x144f/0x5660 [ 53.351641][ T7964] ? is_bpf_text_address+0xd3/0x170 [ 53.356814][ T7964] ? path_lookupat.isra.0+0xba0/0xba0 [ 53.362161][ T7964] ? __lock_acquire+0x572/0x4a10 [ 53.367075][ T7964] ? kmem_cache_alloc+0x12d/0x710 [ 53.372074][ T7964] ? __do_execve_file.isra.0+0x47a/0x2700 [ 53.377766][ T7964] ? __x64_sys_execve+0x8f/0xc0 [ 53.382594][ T7964] ? do_syscall_64+0x1a3/0x800 [ 53.387330][ T7964] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.393383][ T7964] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.399008][ T7964] do_filp_open+0x26f/0x370 [ 53.403492][ T7964] ? may_open_dev+0x100/0x100 [ 53.408147][ T7964] ? refcount_dec_and_mutex_lock+0x90/0x90 [ 53.413931][ T7964] ? prepare_creds+0xa4/0x4e0 [ 53.418598][ T7964] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.424204][ T7964] ? add_lock_to_list.isra.0+0x450/0x450 [ 53.429826][ T7964] ? __do_execve_file.isra.0+0x901/0x2700 [ 53.435520][ T7964] do_open_execat+0x207/0x8e0 [ 53.440175][ T7964] ? unregister_binfmt+0x2b0/0x2b0 [ 53.445266][ T7964] ? kasan_check_read+0x11/0x20 [ 53.450107][ T7964] ? do_raw_spin_trylock+0x270/0x270 [ 53.455367][ T7964] ? __phys_addr_symbol+0x30/0x70 [ 53.460574][ T7964] __do_execve_file.isra.0+0x1966/0x2700 [ 53.466186][ T7964] ? copy_strings_kernel+0x110/0x110 [ 53.471447][ T7964] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 53.477659][ T7964] ? strncpy_from_user+0x3aa/0x4e0 [ 53.482750][ T7964] ? digsig_verify.cold+0x32/0x32 [ 53.487766][ T7964] ? kmem_cache_alloc+0x341/0x710 [ 53.492779][ T7964] ? do_syscall_64+0x8c/0x800 [ 53.497434][ T7964] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 53.503646][ T7964] ? getname_flags+0x277/0x5b0 [ 53.508382][ T7964] ? trace_hardirqs_off_caller+0x300/0x300 [ 53.514165][ T7964] __x64_sys_execve+0x8f/0xc0 [ 53.518820][ T7964] do_syscall_64+0x1a3/0x800 [ 53.523392][ T7964] ? syscall_return_slowpath+0x5f0/0x5f0 [ 53.529017][ T7964] ? prepare_exit_to_usermode+0x3b0/0x3b0 [ 53.534722][ T7964] ? __switch_to_asm+0x34/0x70 [ 53.539470][ T7964] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 53.545001][ T7964] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 53.550876][ T7964] RIP: 0033:0x445709 [ 53.554776][ T7964] Code: e8 ec b8 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 8b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 53.574379][ T7964] RSP: 002b:00007fa6692dcd18 EFLAGS: 00000246 ORIG_RAX: 000000000000003b [ 53.582773][ T7964] RAX: ffffffffffffffda RBX: 00000000006dac58 RCX: 0000000000445709 [ 53.590726][ T7964] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040 [ 53.598676][ T7964] RBP: 00000000006dac50 R08: 68742f636f72702f R09: 68742f636f72702f [ 53.606635][ T7964] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac5c [ 53.614584][ T7964] R13: 00007fa6692dcd20 R14: 0030656c69662f2e R15: 00000000006dad4c