[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.231120] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 27.422003] random: sshd: uninitialized urandom read (32 bytes read) [ 27.894226] random: sshd: uninitialized urandom read (32 bytes read) [ 28.380484] random: sshd: uninitialized urandom read (32 bytes read) [ 32.915171] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.45' (ECDSA) to the list of known hosts. [ 38.447629] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 38.658833] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 38.667246] IP: [<ffffffff836c4abc>] l2tp_session_free+0x11c/0x200 [ 38.673688] PGD 1c6aa7067 [ 38.676331] PUD 1c864c067 PMD 0 [ 38.679822] [ 38.681449] Oops: 0002 [#1] PREEMPT SMP KASAN [ 38.686083] Dumping ftrace buffer: [ 38.689601] (ftrace buffer empty) [ 38.693288] Modules linked in: [ 38.696652] CPU: 1 PID: 3813 Comm: syz-executor457 Not tainted 4.9.123-g520d10d3 #81 [ 38.704518] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 38.713848] task: ffff8801b857e000 task.stack: ffff8801b7058000 [ 38.719882] RIP: 0010:[<ffffffff836c4abc>] [<ffffffff836c4abc>] l2tp_session_free+0x11c/0x200 [ 38.728861] RSP: 0018:ffff8801b705fc98 EFLAGS: 00010246 [ 38.734284] RAX: dffffc0000000000 RBX: ffff8801b7708c80 RCX: 0000000000000000 [ 38.741528] RDX: 1ffff10036e1ad20 RSI: ffffffff836c4a91 RDI: ffff8801b70d6900 [ 38.748777] RBP: ffff8801b705fcb8 R08: ffff8801b857e8e8 R09: 0000000000000000 [ 38.756113] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b70d6780 [ 38.763366] R13: ffff8801b7708c88 R14: 0000000000000000 R15: 0000000000000000 [ 38.770613] FS: 0000000001f96880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 38.778823] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 38.784682] CR2: 0000000000000080 CR3: 00000001c7702000 CR4: 00000000001606f0 [ 38.791929] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 38.799177] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 38.806422] Stack: [ 38.808557] ffff8801b773e600 ffff8801b7708c80 ffff8801b773e9d0 ffff8801b773e8d8 [ 38.816593] ffff8801b705fce0 ffffffff836cc3a2 ffff8801b773ea40 ffff8801b773e600 [ 38.824786] ffffffff836cc2d0 ffff8801b705fd18 ffffffff830281f5 ffff8801b773ea40 [ 38.832887] Call Trace: [ 38.835457] [<ffffffff836cc3a2>] pppol2tp_session_destruct+0xd2/0x110 [ 38.842101] [<ffffffff836cc2d0>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 38.848397] [<ffffffff830281f5>] __sk_destruct+0x55/0x590 [ 38.853998] [<ffffffff8302fc83>] sk_destruct+0x63/0x80 [ 38.859338] [<ffffffff8302fcef>] __sk_free+0x4f/0x220 [ 38.864588] [<ffffffff8302feeb>] sk_free+0x2b/0x40 [ 38.869579] [<ffffffff836cf6a9>] pppol2tp_release+0x239/0x2e0 [ 38.875527] [<ffffffff83018357>] __sock_release+0xd7/0x260 [ 38.881213] [<ffffffff830184e0>] ? __sock_release+0x260/0x260 [ 38.887276] [<ffffffff830184f9>] sock_close+0x19/0x20 [ 38.892558] [<ffffffff8157cb13>] __fput+0x263/0x700 [ 38.897637] [<ffffffff8157d035>] ____fput+0x15/0x20 [ 38.902812] [<ffffffff8119a66c>] task_work_run+0x10c/0x180 [ 38.908512] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 38.914809] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 38.920510] [<ffffffff83a01d93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 38.927412] 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 <f0> 41 ff 8e 80 00 00 00 74 69 e8 e5 c2 c9 fd 4c 89 ea 48 b8 00 [ 38.954630] RIP [<ffffffff836c4abc>] l2tp_session_free+0x11c/0x200 [ 38.961142] RSP <ffff8801b705fc98> [ 38.964741] CR2: 0000000000000080 [ 38.968273] ---[ end trace 8e4e7f940d07729f ]--- [ 38.973040] Kernel panic - not syncing: Fatal exception [ 38.978717] Dumping ftrace buffer: [ 38.982243] (ftrace buffer empty) [ 38.985933] Kernel Offset: disabled [ 38.989542] Rebooting in 86400 seconds..