[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 21.493293] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 25.974743] random: sshd: uninitialized urandom read (32 bytes read) [ 26.598944] random: sshd: uninitialized urandom read (32 bytes read) [ 27.464559] random: sshd: uninitialized urandom read (32 bytes read) [ 164.603596] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.13' (ECDSA) to the list of known hosts. [ 170.161507] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 170.530466] ------------[ cut here ]------------ [ 170.535556] refcount_t: underflow; use-after-free. [ 170.540750] WARNING: CPU: 0 PID: 4589 at lib/refcount.c:187 refcount_sub_and_test+0x2e7/0x350 [ 170.549495] Kernel panic - not syncing: panic_on_warn set ... [ 170.549495] [ 170.556875] CPU: 0 PID: 4589 Comm: syz-executor788 Not tainted 4.18.0-rc3+ #1 [ 170.564227] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 170.574090] Call Trace: [ 170.576771] dump_stack+0x1c9/0x2b4 executing program executing program executing program executing program [ 170.580406] ? dump_stack_print_info.cold.2+0x52/0x52 [ 170.585599] panic+0x238/0x4e7 [ 170.588792] ? add_taint.cold.5+0x16/0x16 [ 170.592941] ? __warn.cold.8+0x148/0x1ba [ 170.597603] ? __warn.cold.8+0x117/0x1ba [ 170.601657] ? refcount_sub_and_test+0x2e7/0x350 [ 170.606718] __warn.cold.8+0x163/0x1ba [ 170.610612] ? refcount_sub_and_test+0x2e7/0x350 [ 170.615359] report_bug+0x252/0x2d0 [ 170.618975] do_error_trap+0x1fc/0x4d0 [ 170.622851] ? math_error+0x3e0/0x3e0 [ 170.626662] ? vprintk_default+0x28/0x30 executing program executing program executing program executing program [ 170.630710] ? vprintk_func+0x81/0xe7 [ 170.634610] ? printk+0xa7/0xcf [ 170.637980] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 170.642819] do_invalid_op+0x1b/0x20 [ 170.646523] invalid_op+0x14/0x20 [ 170.649982] RIP: 0010:refcount_sub_and_test+0x2e7/0x350 [ 170.655326] Code: 89 de e8 2c b7 1c fe 84 db 74 07 31 db e9 46 ff ff ff e8 4c b6 1c fe 48 c7 c7 c0 40 1a 88 c6 05 36 66 3a 06 01 e8 19 d9 e7 fd <0f> 0b 31 db e9 25 ff ff ff 48 8b bd 28 ff ff ff 89 85 34 ff ff ff [ 170.674629] RSP: 0018:ffff8801d8e97780 EFLAGS: 00010286 executing program executing program executing program executing program executing program [ 170.679989] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 170.687245] RDX: 0000000000000000 RSI: ffffffff81631851 RDI: ffff8801d8e97458 [ 170.694500] RBP: ffff8801d8e97868 R08: ffff8801d88b2200 R09: 0000000000000006 [ 170.701757] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff [ 170.709023] R13: ffff8801d8e97840 R14: 0000000000000001 R15: 0000000000000000 [ 170.716314] ? vprintk_func+0x81/0xe7 [ 170.720118] ? refcount_inc_not_zero+0x2f0/0x2f0 [ 170.724881] ? graph_lock+0x170/0x170 executing program executing program executing program executing program [ 170.728683] refcount_dec_and_test+0x1a/0x20 [ 170.733080] smap_release_sock+0x76/0x320 [ 170.737220] ? sock_map_alloc+0x410/0x410 [ 170.741371] sock_hash_ctx_update_elem.isra.27+0x8cb/0x1690 [ 170.747078] ? sock_map_free+0x530/0x530 [ 170.751130] ? rcu_is_watching+0x8c/0x150 [ 170.755363] ? rcu_report_qs_rnp+0x7a0/0x7a0 [ 170.759787] ? __fget+0x414/0x670 [ 170.763232] ? expand_files.part.8+0x9c0/0x9c0 [ 170.767826] ? find_held_lock+0x36/0x1c0 [ 170.771894] sock_hash_update_elem+0x157/0x2f0 [ 170.776500] ? bpf_sock_hash_update+0x90/0x90 executing program executing program executing program executing program [ 170.780999] ? kasan_check_read+0x11/0x20 [ 170.785149] ? rcu_is_watching+0x8c/0x150 [ 170.789293] ? rcu_report_qs_rnp+0x7a0/0x7a0 [ 170.793698] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 170.799228] ? bpf_sock_hash_update+0x90/0x90 [ 170.803712] map_update_elem+0x5c4/0xc90 [ 170.807777] __x64_sys_bpf+0x32d/0x510 [ 170.811668] ? bpf_prog_get+0x20/0x20 [ 170.815463] ? kasan_check_read+0x11/0x20 [ 170.819807] ? _raw_spin_unlock_irq+0x27/0x70 [ 170.824481] ? do_syscall_64+0x9a/0x820 executing program executing program executing program executing program [ 170.828448] do_syscall_64+0x1b9/0x820 [ 170.832505] ? syscall_return_slowpath+0x5e0/0x5e0 [ 170.837990] ? syscall_return_slowpath+0x31d/0x5e0 [ 170.843258] ? entry_SYSCALL_64_after_hwframe+0x59/0xbe [ 170.848656] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 170.853547] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 170.859194] RIP: 0033:0x445fa9 executing program executing program [ 170.862386] Code: e8 7c bf 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 3b 11 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 170.882498] RSP: 002b:00007f0a02e6bce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 [ 170.890480] RAX: ffffffffffffffda RBX: 00000000006dbc3c RCX: 0000000000445fa9 [ 170.897996] RDX: 0000000000000020 RSI: 0000000020000180 RDI: 0000000000000002 [ 170.905251] RBP: 00000000006dbc38 R08: 0000000000000000 R09: 0000000000000000 [ 170.912543] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 170.920565] R13: 00007ffec1d66f0f R14: 00007f0a02e6c9c0 R15: 0000000000000005 [ 170.928778] Dumping ftrace buffer: [ 170.932574] (ftrace buffer empty) [ 170.936376] Kernel Offset: disabled [ 170.939992] Rebooting in 86400 seconds..