[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [ 32.235863][ T26] kauditd_printk_skb: 8 callbacks suppressed [ 32.235872][ T26] audit: type=1800 audit(1547466401.240:29): pid=7236 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rc.local" dev="sda1" ino=2432 res=0 [ 32.268108][ T26] audit: type=1800 audit(1547466401.240:30): pid=7236 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0 Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.152' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 43.247847][ T7392] [ 43.250194][ T7392] ====================================================== [ 43.257182][ T7392] WARNING: possible circular locking dependency detected [ 43.264173][ T7392] 5.0.0-rc1-next-20190114 #11 Not tainted [ 43.269855][ T7392] ------------------------------------------------------ [ 43.276845][ T7392] syz-executor046/7392 is trying to acquire lock: [ 43.283240][ T7392] 00000000e99d9ba9 (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 [ 43.291289][ T7392] [ 43.291289][ T7392] but task is already holding lock: [ 43.298622][ T7392] 00000000645208e5 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 43.308662][ T7392] [ 43.308662][ T7392] which lock already depends on the new lock. [ 43.308662][ T7392] [ 43.319034][ T7392] [ 43.319034][ T7392] the existing dependency chain (in reverse order) is: [ 43.328040][ T7392] [ 43.328040][ T7392] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 43.335737][ T7392] __mutex_lock+0x12f/0x1670 [ 43.340823][ T7392] mutex_lock_interruptible_nested+0x16/0x20 [ 43.347299][ T7392] proc_pid_attr_write+0x200/0x580 [ 43.352904][ T7392] __vfs_write+0x116/0xb40 [ 43.357812][ T7392] __kernel_write+0x110/0x3b0 [ 43.362979][ T7392] write_pipe_buf+0x180/0x240 [ 43.368155][ T7392] __splice_from_pipe+0x39a/0x7e0 [ 43.373670][ T7392] splice_from_pipe+0x1ea/0x310 [ 43.379036][ T7392] default_file_splice_write+0x3c/0x90 [ 43.384997][ T7392] do_splice+0x64b/0x1410 [ 43.389822][ T7392] __x64_sys_splice+0x2c6/0x330 [ 43.395168][ T7392] do_syscall_64+0x1a3/0x800 [ 43.400254][ T7392] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 43.406637][ T7392] [ 43.406637][ T7392] -> #0 (&pipe->mutex/1){+.+.}: [ 43.413639][ T7392] lock_acquire+0x1db/0x570 [ 43.418636][ T7392] __mutex_lock+0x12f/0x1670 [ 43.423718][ T7392] mutex_lock_nested+0x16/0x20 [ 43.428977][ T7392] fifo_open+0x159/0xb00 [ 43.433719][ T7392] do_dentry_open+0x495/0x1230 [ 43.438977][ T7392] vfs_open+0xa0/0xd0 [ 43.443462][ T7392] path_openat+0x144f/0x5660 [ 43.448543][ T7392] do_filp_open+0x26f/0x370 [ 43.453535][ T7392] do_open_execat+0x207/0x8e0 [ 43.458706][ T7392] __do_execve_file.isra.0+0x1966/0x2700 [ 43.464831][ T7392] __x64_sys_execve+0x8f/0xc0 [ 43.470010][ T7392] do_syscall_64+0x1a3/0x800 [ 43.475095][ T7392] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 43.481473][ T7392] [ 43.481473][ T7392] other info that might help us debug this: [ 43.481473][ T7392] [ 43.491668][ T7392] Possible unsafe locking scenario: [ 43.491668][ T7392] [ 43.499089][ T7392] CPU0 CPU1 [ 43.504428][ T7392] ---- ---- [ 43.509765][ T7392] lock(&sig->cred_guard_mutex); [ 43.514761][ T7392] lock(&pipe->mutex/1); [ 43.521588][ T7392] lock(&sig->cred_guard_mutex); [ 43.529102][ T7392] lock(&pipe->mutex/1); [ 43.533400][ T7392] [ 43.533400][ T7392] *** DEADLOCK *** [ 43.533400][ T7392] [ 43.541519][ T7392] 1 lock held by syz-executor046/7392: [ 43.546944][ T7392] #0: 00000000645208e5 (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x45d/0x2700 [ 43.557426][ T7392] [ 43.557426][ T7392] stack backtrace: [ 43.563290][ T7392] CPU: 1 PID: 7392 Comm: syz-executor046 Not tainted 5.0.0-rc1-next-20190114 #11 [ 43.572363][ T7392] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 43.582389][ T7392] Call Trace: [ 43.585660][ T7392] dump_stack+0x1db/0x2d0 [ 43.589961][ T7392] ? dump_stack_print_info.cold+0x20/0x20 [ 43.595661][ T7392] ? print_stack_trace+0x77/0xb0 [ 43.600570][ T7392] ? vprintk_func+0x86/0x189 [ 43.605134][ T7392] print_circular_bug.isra.0.cold+0x1cc/0x28f [ 43.611172][ T7392] __lock_acquire+0x2fed/0x4a10 [ 43.616007][ T7392] ? mark_held_locks+0x100/0x100 [ 43.620915][ T7392] ? lockdep_hardirqs_on+0x415/0x5d0 [ 43.626174][ T7392] ? trace_hardirqs_on+0xbd/0x310 [ 43.631170][ T7392] ? do_raw_spin_trylock+0x270/0x270 [ 43.636430][ T7392] ? unwind_get_return_address+0x61/0xa0 [ 43.642036][ T7392] ? add_lock_to_list.isra.0+0x450/0x450 [ 43.647655][ T7392] ? print_usage_bug+0xd0/0xd0 [ 43.652392][ T7392] ? depot_save_stack+0x1de/0x460 [ 43.657391][ T7392] ? __lock_is_held+0xb6/0x140 [ 43.662125][ T7392] ? save_stack+0xa9/0xd0 [ 43.666428][ T7392] lock_acquire+0x1db/0x570 [ 43.670901][ T7392] ? fifo_open+0x159/0xb00 [ 43.675293][ T7392] ? ___might_sleep+0x1e7/0x310 [ 43.680116][ T7392] ? lock_release+0xc40/0xc40 [ 43.684772][ T7392] ? fifo_open+0x159/0xb00 [ 43.689171][ T7392] ? fifo_open+0x159/0xb00 [ 43.693558][ T7392] __mutex_lock+0x12f/0x1670 [ 43.698143][ T7392] ? fifo_open+0x159/0xb00 [ 43.702532][ T7392] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 43.708754][ T7392] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 43.715133][ T7392] ? fifo_open+0x159/0xb00 [ 43.719521][ T7392] ? lockdep_init_map+0x10c/0x5b0 [ 43.724519][ T7392] ? mutex_trylock+0x2d0/0x2d0 [ 43.729254][ T7392] ? add_lock_to_list.isra.0+0x450/0x450 [ 43.734860][ T7392] ? __mutex_init+0x1f6/0x2a0 [ 43.739512][ T7392] ? psi_task_change.cold+0x1ec/0x1ec [ 43.744859][ T7392] ? fifo_open+0x2b5/0xb00 [ 43.749247][ T7392] ? find_held_lock+0x35/0x120 [ 43.753991][ T7392] ? fifo_open+0x2b5/0xb00 [ 43.758379][ T7392] ? lock_acquire+0x1db/0x570 [ 43.763046][ T7392] ? kasan_check_read+0x11/0x20 [ 43.767870][ T7392] ? do_raw_spin_unlock+0xa0/0x330 [ 43.772960][ T7392] ? do_raw_spin_trylock+0x270/0x270 [ 43.778221][ T7392] mutex_lock_nested+0x16/0x20 [ 43.782963][ T7392] ? mutex_lock_nested+0x16/0x20 [ 43.787873][ T7392] fifo_open+0x159/0xb00 [ 43.792087][ T7392] do_dentry_open+0x495/0x1230 [ 43.796824][ T7392] ? do_raw_spin_unlock+0xa0/0x330 [ 43.801908][ T7392] ? pipe_release+0x280/0x280 [ 43.806569][ T7392] ? chown_common+0x740/0x740 [ 43.811218][ T7392] ? security_inode_permission+0xd5/0x110 [ 43.816912][ T7392] ? inode_permission+0xb4/0x570 [ 43.821823][ T7392] vfs_open+0xa0/0xd0 [ 43.825780][ T7392] path_openat+0x144f/0x5660 [ 43.830350][ T7392] ? kernel_text_address+0x73/0xf0 [ 43.835433][ T7392] ? __kernel_text_address+0xd/0x40 [ 43.840600][ T7392] ? unwind_get_return_address+0x61/0xa0 [ 43.846215][ T7392] ? path_lookupat.isra.0+0xba0/0xba0 [ 43.851561][ T7392] ? save_stack+0xa9/0xd0 [ 43.855872][ T7392] ? save_stack+0x45/0xd0 [ 43.860173][ T7392] ? __kasan_kmalloc.constprop.0+0xcf/0xe0 [ 43.865957][ T7392] ? kasan_kmalloc+0x9/0x10 [ 43.870433][ T7392] ? __lock_acquire+0x572/0x4a10 [ 43.875340][ T7392] ? kmem_cache_alloc+0x12d/0x710 [ 43.880335][ T7392] ? __do_execve_file.isra.0+0x47a/0x2700 [ 43.886025][ T7392] ? __x64_sys_execve+0x8f/0xc0 [ 43.890858][ T7392] ? print_usage_bug+0xd0/0xd0 [ 43.895599][ T7392] do_filp_open+0x26f/0x370 [ 43.900071][ T7392] ? may_open_dev+0x100/0x100 [ 43.904722][ T7392] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x20 [ 43.910935][ T7392] ? add_lock_to_list.isra.0+0x450/0x450 [ 43.916548][ T7392] ? add_lock_to_list.isra.0+0x450/0x450 [ 43.922154][ T7392] ? apparmor_bprm_committing_creds+0x370/0x370 [ 43.928367][ T7392] ? __do_execve_file.isra.0+0x901/0x2700 [ 43.934059][ T7392] do_open_execat+0x207/0x8e0 [ 43.938712][ T7392] ? unregister_binfmt+0x2b0/0x2b0 [ 43.943796][ T7392] ? kasan_check_read+0x11/0x20 [ 43.948618][ T7392] ? do_raw_spin_trylock+0x270/0x270 [ 43.953876][ T7392] ? __phys_addr_symbol+0x30/0x70 [ 43.958873][ T7392] __do_execve_file.isra.0+0x1966/0x2700 [ 43.964477][ T7392] ? copy_strings_kernel+0x110/0x110 [ 43.969733][ T7392] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 43.975952][ T7392] ? strncpy_from_user+0x3aa/0x4e0 [ 43.981035][ T7392] ? digsig_verify.cold+0x32/0x32 [ 43.986030][ T7392] ? kmem_cache_alloc+0x341/0x710 [ 43.991025][ T7392] ? do_syscall_64+0x8c/0x800 [ 43.995676][ T7392] ? lockdep_hardirqs_on+0x415/0x5d0 [ 44.000947][ T7392] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 44.007162][ T7392] ? getname_flags+0x277/0x5b0 [ 44.011899][ T7392] ? trace_hardirqs_off_caller+0x300/0x300 [ 44.017676][ T7392] __x64_sys_execve+0x8f/0xc0 [ 44.022326][ T7392] do_syscall_64+0x1a3/0x800 [ 44.026896][ T7392] ? syscall_return_slowpath+0x5f0/0x5f0 [ 44.032509][ T7392] ? prepare_exit_to_usermode+0x3b0/0x3b0 [ 44.038205][ T7392] ? __switch_to_asm+0x34/0x70 [ 44.042948][ T7392] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 44.048469][ T7392] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 44.054333][ T7392] RIP: 0033:0x445719 [ 44.058205][ T7392] 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 [ 44.077781][ T7392] RSP: 002b:00007f41b10d1da8 EFLAGS: 00000246 ORIG_RAX: 000000000000003b [ 44.086162][ T7392] RAX: ffffffffffffffda RBX: 00000000006dac58 RCX: 0000000000445719 [ 44.094106][ T7392] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040