[ OK ] Started Getty on tty4. [ OK ] Started Getty on tty3. [ OK ] Started Getty on tty2. [ OK ] Started Getty on tty1. [ OK ] Started Serial Getty on ttyS0. [ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.41' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 62.037359][ T7037] IPVS: ftp: loaded support on port[0] = 21 [ 62.077210][ T7037] netlink: 16 bytes leftover after parsing attributes in process `syz-executor732'. [ 62.133662][ T7037] ------------[ cut here ]------------ [ 62.139218][ T7037] refcount_t: underflow; use-after-free. [ 62.146177][ T7037] WARNING: CPU: 0 PID: 7037 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 [ 62.155636][ T7037] Kernel panic - not syncing: panic_on_warn set ... [ 62.162255][ T7037] CPU: 0 PID: 7037 Comm: syz-executor732 Not tainted 5.6.0-next-20200408-syzkaller #0 [ 62.171779][ T7037] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 62.181912][ T7037] Call Trace: [ 62.185208][ T7037] dump_stack+0x188/0x20d [ 62.189530][ T7037] ? refcount_warn_saturate+0xe0/0x1e0 [ 62.195144][ T7037] panic+0x2e3/0x75c [ 62.199151][ T7037] ? add_taint.cold+0x16/0x16 [ 62.203905][ T7037] ? __probe_kernel_read+0x188/0x1d0 [ 62.209226][ T7037] ? __warn.cold+0x14/0x35 [ 62.213632][ T7037] ? __warn+0xd5/0x1c8 [ 62.217691][ T7037] ? refcount_warn_saturate+0x1d1/0x1e0 [ 62.223229][ T7037] __warn.cold+0x2f/0x35 [ 62.227578][ T7037] ? refcount_warn_saturate+0x1d1/0x1e0 [ 62.233114][ T7037] report_bug+0x27b/0x2f0 [ 62.237451][ T7037] do_error_trap+0x12b/0x220 [ 62.242028][ T7037] ? refcount_warn_saturate+0x1d1/0x1e0 [ 62.247567][ T7037] do_invalid_op+0x32/0x40 [ 62.252105][ T7037] ? refcount_warn_saturate+0x1d1/0x1e0 [ 62.259125][ T7037] invalid_op+0x23/0x30 [ 62.263427][ T7037] RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 [ 62.269574][ T7037] Code: e9 db fe ff ff 48 89 df e8 8c 5f 1a fe e9 8a fe ff ff e8 f2 55 dc fd 48 c7 c7 40 66 72 88 c6 05 6d a9 ed 06 01 e8 77 88 ad fd <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55 [ 62.289170][ T7037] RSP: 0018:ffffc9000565fd38 EFLAGS: 00010286 [ 62.295367][ T7037] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 62.303459][ T7037] RDX: 0000000000000000 RSI: ffffffff815cd441 RDI: fffff52000acbf99 [ 62.312532][ T7037] RBP: 0000000000000003 R08: ffff8880987184c0 R09: ffffed1015cc66b1 [ 62.320494][ T7037] R10: ffff8880ae633587 R11: ffffed1015cc66b0 R12: ffff88809870a040 [ 62.328542][ T7037] R13: ffff88809870a044 R14: 00000000000002ab R15: ffff8880a71ae200 [ 62.336581][ T7037] ? vprintk_func+0x81/0x17e [ 62.341164][ T7037] ? refcount_warn_saturate+0x1d1/0x1e0 [ 62.346740][ T7037] free_nsproxy+0x445/0x4a0 [ 62.351243][ T7037] switch_task_namespaces+0xaa/0xc0 [ 62.356441][ T7037] do_exit+0xb4e/0x2e10 [ 62.360622][ T7037] ? mm_update_next_owner+0x7a0/0x7a0 [ 62.366250][ T7037] ? up_read+0x1a8/0x750 [ 62.370637][ T7037] ? down_read_nested+0x430/0x430 [ 62.375664][ T7037] ? handle_mm_fault+0x29e/0x660 [ 62.380604][ T7037] do_group_exit+0x125/0x340 [ 62.385317][ T7037] __x64_sys_exit_group+0x3a/0x50 [ 62.390350][ T7037] do_syscall_64+0xf6/0x7d0 [ 62.394976][ T7037] entry_SYSCALL_64_after_hwframe+0x49/0xb3 [ 62.401032][ T7037] RIP: 0033:0x43f998 [ 62.404939][ T7037] Code: Bad RIP value. [ 62.409241][ T7037] RSP: 002b:00007fffd3c5ea78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 62.417777][ T7037] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 000000000043f998 [ 62.426181][ T7037] RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001 [ 62.434172][ T7037] RBP: 00000000004bfa10 R08: 00000000000000e7 R09: ffffffffffffffd0 [ 62.442514][ T7037] R10: 0000000120080522 R11: 0000000000000246 R12: 0000000000000001 [ 62.450477][ T7037] R13: 00000000006d11c0 R14: 0000000000000000 R15: 0000000000000000 [ 62.460608][ T7037] Kernel Offset: disabled [ 62.465221][ T7037] Rebooting in 86400 seconds..