[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.818857] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.624559] random: sshd: uninitialized urandom read (32 bytes read) [ 22.015783] random: sshd: uninitialized urandom read (32 bytes read) [ 22.551778] random: sshd: uninitialized urandom read (32 bytes read) [ 27.513139] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.1' (ECDSA) to the list of known hosts. [ 33.228436] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 33.434565] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 33.442967] IP: [] l2tp_session_free+0x11c/0x200 [ 33.449400] PGD 1c2247067 [ 33.452044] PUD 1c141e067 PMD 0 [ 33.455532] [ 33.457165] Oops: 0002 [#1] PREEMPT SMP KASAN [ 33.461635] Dumping ftrace buffer: [ 33.465164] (ftrace buffer empty) [ 33.468854] Modules linked in: [ 33.472163] CPU: 1 PID: 3759 Comm: syz-executor632 Not tainted 4.9.124-g09eb2ba #31 [ 33.479943] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 33.489285] task: ffff8801bd8ee000 task.stack: ffff8801bc1c8000 [ 33.495317] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 33.504186] RSP: 0018:ffff8801bc1cfc98 EFLAGS: 00010246 [ 33.509616] RAX: dffffc0000000000 RBX: ffff8801ca6f9900 RCX: 0000000000000000 [ 33.516877] RDX: 1ffff10037848970 RSI: ffffffff836c4711 RDI: ffff8801bc244b80 [ 33.524130] RBP: ffff8801bc1cfcb8 R08: ffff8801bd8ee8e8 R09: 0000000000000000 [ 33.531384] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801bc244a00 [ 33.538641] R13: ffff8801ca6f9908 R14: 0000000000000000 R15: 0000000000000000 [ 33.545895] FS: 0000000001f13880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 33.554107] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 33.559980] CR2: 0000000000000080 CR3: 00000001c1573000 CR4: 00000000001606f0 [ 33.567345] Stack: [ 33.569475] ffff8801d57ac400 ffff8801ca6f9900 ffff8801d57ac7d0 ffff8801d57ac6d8 [ 33.577493] ffff8801bc1cfce0 ffffffff836cc022 ffff8801d57ac840 ffff8801d57ac400 [ 33.585697] ffffffff836cbf50 ffff8801bc1cfd18 ffffffff830281f5 ffff8801d57ac840 [ 33.593776] Call Trace: [ 33.596351] [] pppol2tp_session_destruct+0xd2/0x110 [ 33.602997] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 33.609310] [] __sk_destruct+0x55/0x590 [ 33.614929] [] sk_destruct+0x63/0x80 [ 33.620412] [] __sk_free+0x4f/0x220 [ 33.625670] [] sk_free+0x2b/0x40 [ 33.630671] [] pppol2tp_release+0x239/0x2e0 [ 33.636627] [] __sock_release+0xd7/0x260 [ 33.642323] [] ? __sock_release+0x260/0x260 [ 33.648286] [] sock_close+0x19/0x20 [ 33.653549] [] __fput+0x263/0x700 [ 33.658656] [] ____fput+0x15/0x20 [ 33.663825] [] task_work_run+0x10c/0x180 [ 33.669542] [] exit_to_usermode_loop+0xfc/0x120 [ 33.675841] [] do_syscall_64+0x364/0x490 [ 33.681535] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 33.688438] Code: 49 8d bc 24 80 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 c6 00 00 00 4d 8b b4 24 80 01 00 00 41 ff 8e 80 00 00 00 74 69 e8 a5 c5 c9 fd 4c 89 ea 48 b8 00 [ 33.715485] RIP [] l2tp_session_free+0x11c/0x200 [ 33.722104] RSP [ 33.725708] CR2: 0000000000000080 [ 33.729447] ---[ end trace 337db620c01e4434 ]--- [ 33.735549] Kernel panic - not syncing: Fatal exception [ 33.741472] Dumping ftrace buffer: [ 33.744998] (ftrace buffer empty) [ 33.748688] Kernel Offset: disabled [ 33.752291] Rebooting in 86400 seconds..