[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 46.193825][ T27] audit: type=1800 audit(1584420554.761:25): pid=8448 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 46.212799][ T27] audit: type=1800 audit(1584420554.761:26): pid=8448 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 46.262644][ T27] audit: type=1800 audit(1584420554.761:27): pid=8448 uid=0 auid=4294967295 ses=4294967295 subj=_ 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 '10.128.0.86' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 58.253306][ T8602] IPVS: ftp: loaded support on port[0] = 21 [ 58.282036][ T8602] netlink: 16 bytes leftover after parsing attributes in process `syz-executor780'. [ 58.350645][ T8602] ------------[ cut here ]------------ [ 58.356131][ T8602] refcount_t: underflow; use-after-free. [ 58.362026][ T8602] WARNING: CPU: 1 PID: 8602 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 [ 58.371433][ T8602] Kernel panic - not syncing: panic_on_warn set ... [ 58.377996][ T8602] CPU: 1 PID: 8602 Comm: syz-executor780 Not tainted 5.6.0-rc6-syzkaller #0 [ 58.386650][ T8602] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 58.396728][ T8602] Call Trace: [ 58.400015][ T8602] dump_stack+0x1e9/0x30e [ 58.404335][ T8602] panic+0x264/0x7a0 [ 58.408208][ T8602] ? __warn+0x102/0x210 [ 58.412343][ T8602] ? refcount_warn_saturate+0x15b/0x1a0 [ 58.417960][ T8602] __warn+0x209/0x210 [ 58.421957][ T8602] ? refcount_warn_saturate+0x15b/0x1a0 [ 58.427473][ T8602] report_bug+0x1ac/0x2d0 [ 58.431783][ T8602] do_error_trap+0xca/0x1c0 [ 58.436301][ T8602] do_invalid_op+0x32/0x40 [ 58.440704][ T8602] ? refcount_warn_saturate+0x15b/0x1a0 [ 58.446223][ T8602] invalid_op+0x23/0x30 [ 58.450393][ T8602] RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 [ 58.456520][ T8602] Code: c7 14 00 d1 88 31 c0 e8 53 38 b3 fd 0f 0b eb 85 e8 da 59 e0 fd c6 05 2e 86 b1 05 01 48 c7 c7 40 00 d1 88 31 c0 e8 35 38 b3 fd <0f> 0b e9 64 ff ff ff e8 b9 59 e0 fd c6 05 0e 86 b1 05 01 48 c7 c7 [ 58.476196][ T8602] RSP: 0018:ffffc90001fb7d98 EFLAGS: 00010246 [ 58.482246][ T8602] RAX: 5a8c0684d58bff00 RBX: 0000000000000003 RCX: ffff8880a2d80340 [ 58.490197][ T8602] RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 [ 58.498158][ T8602] RBP: 0000000000000003 R08: ffffffff815e17a6 R09: fffffbfff121afc3 [ 58.506127][ T8602] R10: fffffbfff121afc3 R11: 0000000000000000 R12: ffff888096df4040 [ 58.514085][ T8602] R13: 0000000000000100 R14: ffff8880a9a7db60 R15: ffff888096df4044 [ 58.522048][ T8602] ? vprintk_emit+0x2e6/0x3b0 [ 58.526797][ T8602] ? refcount_warn_saturate+0x15b/0x1a0 [ 58.532317][ T8602] free_nsproxy+0x343/0x3b0 [ 58.536796][ T8602] do_exit+0x5ea/0x1f80 [ 58.540960][ T8602] ? __up_read+0x1f1/0x6e0 [ 58.545380][ T8602] do_group_exit+0x15e/0x2c0 [ 58.549956][ T8602] ? trace_irq_disable_rcuidle+0x1f/0x1d0 [ 58.555664][ T8602] __do_sys_exit_group+0x13/0x20 [ 58.560598][ T8602] __se_sys_exit_group+0x10/0x10 [ 58.565526][ T8602] __x64_sys_exit_group+0x37/0x40 [ 58.570538][ T8602] do_syscall_64+0xf3/0x1b0 [ 58.575025][ T8602] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 58.580905][ T8602] RIP: 0033:0x43f998 [ 58.584790][ T8602] Code: 24 38 80 f9 3a 0f 85 5f 01 00 00 48 8d 74 24 34 48 8d 7c 24 38 83 ea 01 89 54 24 34 e8 61 f8 ff ff 83 f8 3c 41 89 c1 0f 87 3d <01> 00 00 8b 4c 24 34 85 c9 0f 8e 59 01 00 00 48 8b 54 24 38 c7 44 [ 58.604369][ T8602] RSP: 002b:00007fff215c0c58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 58.612798][ T8602] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 000000000043f998 [ 58.620759][ T8602] RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001 [ 58.628708][ T8602] RBP: 00000000004bfa10 R08: 00000000000000e7 R09: ffffffffffffffd0 [ 58.636657][ T8602] R10: 0000000120080522 R11: 0000000000000246 R12: 0000000000000001 [ 58.644606][ T8602] R13: 00000000006d11c0 R14: 0000000000000000 R15: 0000000000000000 [ 58.653818][ T8602] Kernel Offset: disabled [ 58.658221][ T8602] Rebooting in 86400 seconds..