[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 74.720385][ T23] audit: type=1800 audit(1581671449.991:25): pid=9635 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 74.740652][ T23] audit: type=1800 audit(1581671449.991:26): pid=9635 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 74.796063][ T23] audit: type=1800 audit(1581671449.991:27): pid=9635 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 '10.128.0.255' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 85.426084][ T9787] [ 85.428673][ T9787] ====================================================== [ 85.435666][ T9787] WARNING: possible circular locking dependency detected [ 85.442676][ T9787] 5.6.0-rc1-next-20200214-syzkaller #0 Not tainted [ 85.449170][ T9787] ------------------------------------------------------ [ 85.456605][ T9787] syz-executor167/9787 is trying to acquire lock: [ 85.462991][ T9787] ffff88809a1872a0 (&tty->termios_rwsem){++++}, at: n_tty_receive_buf_common+0x8a/0x2b70 [ 85.472781][ T9787] [ 85.472781][ T9787] but task is already holding lock: [ 85.480126][ T9787] ffffffff8a1414c0 (sel_lock){+.+.}, at: paste_selection+0x15a/0x4d0 [ 85.488185][ T9787] [ 85.488185][ T9787] which lock already depends on the new lock. [ 85.488185][ T9787] [ 85.498631][ T9787] [ 85.498631][ T9787] the existing dependency chain (in reverse order) is: [ 85.507624][ T9787] [ 85.507624][ T9787] -> #2 (sel_lock){+.+.}: [ 85.514181][ T9787] __mutex_lock+0x156/0x13c0 [ 85.519270][ T9787] mutex_lock_nested+0x16/0x20 [ 85.524546][ T9787] set_selection_kernel+0x39d/0x13d0 [ 85.530338][ T9787] set_selection_user+0x95/0xd9 [ 85.535701][ T9787] tioclinux+0x11c/0x480 [ 85.540447][ T9787] vt_ioctl+0x1a41/0x26c0 [ 85.545280][ T9787] tty_ioctl+0xa37/0x14f0 [ 85.550215][ T9787] ksys_ioctl+0x123/0x180 [ 85.555042][ T9787] __x64_sys_ioctl+0x73/0xb0 [ 85.560149][ T9787] do_syscall_64+0xfa/0x790 [ 85.565158][ T9787] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 85.571548][ T9787] [ 85.571548][ T9787] -> #1 (console_lock){+.+.}: [ 85.578397][ T9787] console_lock+0x47/0x80 [ 85.583260][ T9787] con_flush_chars+0x3d/0xa0 [ 85.588367][ T9787] n_tty_write+0xc85/0x1080 [ 85.593424][ T9787] tty_write+0x496/0x7f0 [ 85.598179][ T9787] __vfs_write+0x8a/0x110 [ 85.603036][ T9787] vfs_write+0x268/0x5d0 [ 85.607782][ T9787] ksys_write+0x14f/0x290 [ 85.612606][ T9787] __x64_sys_write+0x73/0xb0 [ 85.617700][ T9787] do_syscall_64+0xfa/0x790 [ 85.622709][ T9787] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 85.629095][ T9787] [ 85.629095][ T9787] -> #0 (&tty->termios_rwsem){++++}: [ 85.637101][ T9787] __lock_acquire+0x29cd/0x6320 [ 85.642484][ T9787] lock_acquire+0x190/0x410 [ 85.647490][ T9787] down_read+0x95/0x440 [ 85.652149][ T9787] n_tty_receive_buf_common+0x8a/0x2b70 [ 85.658271][ T9787] n_tty_receive_buf2+0x34/0x40 [ 85.663624][ T9787] tty_ldisc_receive_buf+0xad/0x1c0 [ 85.669325][ T9787] paste_selection+0x1ff/0x4d0 [ 85.674618][ T9787] tioclinux+0x133/0x480 [ 85.679356][ T9787] vt_ioctl+0x1a41/0x26c0 [ 85.684211][ T9787] tty_ioctl+0xa37/0x14f0 [ 85.689060][ T9787] ksys_ioctl+0x123/0x180 [ 85.693894][ T9787] __x64_sys_ioctl+0x73/0xb0 [ 85.698993][ T9787] do_syscall_64+0xfa/0x790 [ 85.704035][ T9787] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 85.710440][ T9787] [ 85.710440][ T9787] other info that might help us debug this: [ 85.710440][ T9787] [ 85.720652][ T9787] Chain exists of: [ 85.720652][ T9787] &tty->termios_rwsem --> console_lock --> sel_lock [ 85.720652][ T9787] [ 85.733121][ T9787] Possible unsafe locking scenario: [ 85.733121][ T9787] [ 85.740552][ T9787] CPU0 CPU1 [ 85.745898][ T9787] ---- ---- [ 85.751244][ T9787] lock(sel_lock); [ 85.755029][ T9787] lock(console_lock); [ 85.761678][ T9787] lock(sel_lock); [ 85.768765][ T9787] lock(&tty->termios_rwsem); [ 85.773651][ T9787] [ 85.773651][ T9787] *** DEADLOCK *** [ 85.773651][ T9787] [ 85.781804][ T9787] 3 locks held by syz-executor167/9787: [ 85.787331][ T9787] #0: ffff88809a187090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 [ 85.796258][ T9787] #1: ffff8880aa5be0a8 (&buf->lock){+.+.}, at: tty_buffer_lock_exclusive+0x30/0x40 [ 85.805875][ T9787] #2: ffffffff8a1414c0 (sel_lock){+.+.}, at: paste_selection+0x15a/0x4d0 [ 85.814367][ T9787] [ 85.814367][ T9787] stack backtrace: [ 85.820447][ T9787] CPU: 1 PID: 9787 Comm: syz-executor167 Not tainted 5.6.0-rc1-next-20200214-syzkaller #0 [ 85.830380][ T9787] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 85.840566][ T9787] Call Trace: [ 85.844131][ T9787] dump_stack+0x197/0x210 [ 85.848469][ T9787] print_circular_bug.isra.0.cold+0x163/0x172 [ 85.854636][ T9787] check_noncircular+0x32e/0x3e0 [ 85.859557][ T9787] ? print_circular_bug.isra.0+0x230/0x230 [ 85.866307][ T9787] ? alloc_list_entry+0xc0/0xc0 [ 85.871241][ T9787] ? mark_lock+0xc2/0x1220 [ 85.875676][ T9787] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 85.881896][ T9787] ? find_first_zero_bit+0x9a/0xc0 [ 85.887157][ T9787] __lock_acquire+0x29cd/0x6320 [ 85.892219][ T9787] ? save_trace+0x49/0x830 [ 85.896627][ T9787] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 85.902900][ T9787] ? mark_held_locks+0xf0/0xf0 [ 85.907672][ T9787] lock_acquire+0x190/0x410 [ 85.912190][ T9787] ? n_tty_receive_buf_common+0x8a/0x2b70 [ 85.917896][ T9787] down_read+0x95/0x440 [ 85.922473][ T9787] ? n_tty_receive_buf_common+0x8a/0x2b70 [ 85.928187][ T9787] ? down_read_killable+0x490/0x490 [ 85.933377][ T9787] n_tty_receive_buf_common+0x8a/0x2b70 [ 85.938935][ T9787] ? paste_selection+0x15a/0x4d0 [ 85.943858][ T9787] ? mark_lock+0xc2/0x1220 [ 85.948257][ T9787] ? mutex_trylock+0x2d0/0x2d0 [ 85.953290][ T9787] ? mark_held_locks+0xa4/0xf0 [ 85.958086][ T9787] ? lockdep_hardirqs_on+0x421/0x5e0 [ 85.963737][ T9787] n_tty_receive_buf2+0x34/0x40 [ 85.968587][ T9787] tty_ldisc_receive_buf+0xad/0x1c0 [ 85.973860][ T9787] ? n_tty_receive_buf_common+0x2b70/0x2b70 [ 85.979844][ T9787] paste_selection+0x1ff/0x4d0 [ 85.984595][ T9787] ? sel_pos+0x90/0x90 [ 85.988679][ T9787] ? lock_downgrade+0x920/0x920 [ 85.993637][ T9787] ? wake_up_q+0x140/0x140 [ 85.998082][ T9787] tioclinux+0x133/0x480 [ 86.002336][ T9787] vt_ioctl+0x1a41/0x26c0 [ 86.007444][ T9787] ? complete_change_console+0x3a0/0x3a0 [ 86.013077][ T9787] ? tomoyo_execute_permission+0x4a0/0x4a0 [ 86.018973][ T9787] ? __sanitizer_cov_trace_switch+0x49/0x80 [ 86.024882][ T9787] ? tty_jobctrl_ioctl+0x50/0xd40 [ 86.029917][ T9787] ? complete_change_console+0x3a0/0x3a0 [ 86.036366][ T9787] tty_ioctl+0xa37/0x14f0 [ 86.040677][ T9787] ? tty_vhangup+0x30/0x30 [ 86.045080][ T9787] ? __sanitizer_cov_trace_const_cmp2+0x18/0x20 [ 86.051331][ T9787] ? do_vfs_ioctl+0x568/0x13b0 [ 86.056147][ T9787] ? ioctl_file_clone+0x180/0x180 [ 86.061159][ T9787] ? file_open_root+0x430/0x430 [ 86.066036][ T9787] ? tomoyo_file_ioctl+0x23/0x30 [ 86.070997][ T9787] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 86.077272][ T9787] ? security_file_ioctl+0x8d/0xc0 [ 86.082476][ T9787] ? tty_vhangup+0x30/0x30 [ 86.086882][ T9787] ksys_ioctl+0x123/0x180 [ 86.091223][ T9787] __x64_sys_ioctl+0x73/0xb0 [ 86.095818][ T9787] do_syscall_64+0xfa/0x790 [ 86.100319][ T9787] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 86.106302][ T9787] RIP: 0033:0x440219 [ 86.110206][ T9787] 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 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 86.131599][ T9787] RSP: 002b:00007ffe5133a1c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 86.140324][ T9787] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440219 [ 86.148346][ T9787] RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000004 [ 86.156394][ T9787] RBP: 00000000006ca018 R08: 000000000000000d R09: 00000000004002c8 [ 86.164353][ T9787] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b00 [ 86.172313][ T9787] R13: 0000000000401b90 R14: 0000000000000000 R15: 000000000