[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.665456] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 22.031640] random: sshd: uninitialized urandom read (32 bytes read) [ 22.342380] random: sshd: uninitialized urandom read (32 bytes read) [ 23.180989] random: sshd: uninitialized urandom read (32 bytes read) [ 23.343897] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.49' (ECDSA) to the list of known hosts. [ 28.883629] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 28.991932] device lo entered promiscuous mode [ 29.064254] ------------[ cut here ]------------ [ 29.069140] refcount_t: underflow; use-after-free. [ 29.074294] WARNING: CPU: 0 PID: 4571 at lib/refcount.c:187 refcount_sub_and_test+0x2e7/0x350 [ 29.082950] Kernel panic - not syncing: panic_on_warn set ... [ 29.082950] [ 29.090314] CPU: 0 PID: 4571 Comm: syz-executor167 Not tainted 4.18.0-rc1+ #112 [ 29.097760] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.107107] Call Trace: [ 29.109695] dump_stack+0x1c9/0x2b4 executing program [ 29.113346] ? dump_stack_print_info.cold.2+0x52/0x52 [ 29.118528] panic+0x238/0x4e7 [ 29.121718] ? add_taint.cold.5+0x16/0x16 [ 29.125874] ? __warn.cold.8+0x148/0x1ba [ 29.129929] ? __warn.cold.8+0x117/0x1ba [ 29.133976] ? refcount_sub_and_test+0x2e7/0x350 [ 29.138725] __warn.cold.8+0x163/0x1ba [ 29.142593] ? refcount_sub_and_test+0x2e7/0x350 [ 29.147333] report_bug+0x252/0x2d0 [ 29.150946] do_error_trap+0x1fc/0x4d0 [ 29.154816] ? do_raw_spin_unlock+0xa7/0x2f0 [ 29.159232] ? math_error+0x3f0/0x3f0 [ 29.163019] ? vprintk_default+0x28/0x30 [ 29.167066] ? vprintk_func+0x81/0xe7 [ 29.170849] ? printk+0xa7/0xcf [ 29.174118] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 29.178946] do_invalid_op+0x1b/0x20 [ 29.182646] invalid_op+0x14/0x20 [ 29.186084] RIP: 0010:refcount_sub_and_test+0x2e7/0x350 [ 29.191436] Code: 89 de e8 2c c6 1c fe 84 db 74 07 31 db e9 46 ff ff ff e8 4c c5 1c fe 48 c7 c7 40 6e 1a 88 c6 05 26 4f 3a 06 01 e8 39 e5 e7 fd <0f> 0b 31 db e9 25 ff ff ff 48 8b bd 28 ff ff ff 89 85 34 ff ff ff [ 29.210649] RSP: 0018:ffff8801d8cef800 EFLAGS: 00010282 [ 29.215995] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 29.223252] RDX: 0000000000000000 RSI: ffffffff816318e1 RDI: ffff8801d8cef4d8 [ 29.230504] RBP: ffff8801d8cef8e8 R08: ffff8801ac91a3c0 R09: 0000000000000006 [ 29.237759] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff [ 29.245023] R13: ffff8801d8cef8c0 R14: 0000000000000001 R15: ffff8801acd55500 [ 29.252289] ? vprintk_func+0x81/0xe7 [ 29.256078] ? refcount_inc_not_zero+0x2f0/0x2f0 [ 29.260817] ? graph_lock+0x170/0x170 [ 29.264616] ? debug_check_no_obj_freed+0x30b/0x595 [ 29.269613] ? __lock_is_held+0xb5/0x140 [ 29.273664] refcount_dec_and_test+0x1a/0x20 [ 29.278058] smap_release_sock+0x76/0x300 [ 29.282208] ? free_htab_elem+0x40/0x40 [ 29.286179] sock_hash_ctx_update_elem.isra.24+0x89e/0x1580 [ 29.291893] ? smap_read_sock_strparser+0xcc0/0xcc0 [ 29.297763] ? __fget+0x414/0x670 [ 29.301208] ? expand_files.part.8+0x9c0/0x9c0 [ 29.305778] ? find_held_lock+0x36/0x1c0 [ 29.309833] sock_hash_update_elem+0x157/0x2f0 [ 29.314400] ? bpf_sock_hash_update+0x90/0x90 [ 29.318882] ? kasan_check_read+0x11/0x20 [ 29.323016] ? rcu_is_watching+0x8c/0x150 [ 29.327152] ? rcu_report_qs_rnp+0x7a0/0x7a0 [ 29.331547] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 29.337068] ? bpf_sock_hash_update+0x90/0x90 [ 29.341546] map_update_elem+0x5c4/0xc90 [ 29.345593] __x64_sys_bpf+0x32d/0x510 [ 29.349467] ? bpf_prog_get+0x20/0x20 [ 29.353253] ? ksys_ioctl+0x81/0xd0 [ 29.356863] ? do_syscall_64+0x9a/0x820 [ 29.360823] do_syscall_64+0x1b9/0x820 [ 29.364695] ? syscall_return_slowpath+0x5e0/0x5e0 [ 29.369613] ? syscall_return_slowpath+0x31d/0x5e0 [ 29.374530] ? entry_SYSCALL_64_after_hwframe+0x59/0xbe [ 29.379878] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 29.384720] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 29.389890] RIP: 0033:0x445a69 [ 29.393494] Code: e8 3c 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 db 51 00 00 c3 66 2e 0f 1f 84 00 00 00 00 [ 29.412745] RSP: 002b:00007ff77d9d3db8 EFLAGS: 00000293 ORIG_RAX: 0000000000000141 [ 29.420442] RAX: ffffffffffffffda RBX: 00000000006dac94 RCX: 0000000000445a69 [ 29.427700] RDX: 0000000000000020 RSI: 0000000020000180 RDI: 0000000000000002 [ 29.434952] RBP: 00000000006dac90 R08: 0000000000000000 R09: 0000000000000000 [ 29.442212] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000 [ 29.449469] R13: 00007fff6f3a3c3f R14: 00007ff77d9d49c0 R15: 0000000000000001 [ 29.457504] Dumping ftrace buffer: [ 29.461143] (ftrace buffer empty) [ 29.464842] Kernel Offset: disabled [ 29.468464] Rebooting in 86400 seconds..