[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 16.868493] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 20.911302] random: sshd: uninitialized urandom read (32 bytes read) [ 21.457558] random: sshd: uninitialized urandom read (32 bytes read) [ 21.950328] random: sshd: uninitialized urandom read (32 bytes read) [ 22.341977] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.63' (ECDSA) to the list of known hosts. [ 28.158513] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 28.383599] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 28.391870] IP: [] l2tp_session_free+0x11c/0x200 [ 28.398307] PGD 1b6501067 [ 28.400953] PUD 1b67e6067 PMD 0 [ 28.404510] [ 28.406199] Oops: 0002 [#1] PREEMPT SMP KASAN [ 28.410679] Dumping ftrace buffer: [ 28.414195] (ftrace buffer empty) [ 28.417887] Modules linked in: [ 28.421183] CPU: 0 PID: 3819 Comm: syz-executor641 Not tainted 4.9.120-gf85543b #24 [ 28.428996] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.438335] task: ffff8801b6754800 task.stack: ffff8801b54e8000 [ 28.444368] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 28.453227] RSP: 0018:ffff8801b54efca0 EFLAGS: 00010246 [ 28.458655] RAX: dffffc0000000000 RBX: ffff8801b54d8a00 RCX: 0000000000000000 [ 28.465905] RDX: 1ffff10039627030 RSI: ffffffff836c29a1 RDI: ffff8801cb138180 [ 28.473156] RBP: ffff8801b54efcc0 R08: ffff8801b67550e8 R09: 0000000000000000 [ 28.480540] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801cb138000 [ 28.487791] R13: ffff8801b54d8a08 R14: 0000000000000000 R15: ffffffff83018be0 [ 28.495044] FS: 0000000000890880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 28.503250] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 28.509108] CR2: 0000000000000080 CR3: 00000001c26f1000 CR4: 00000000001606f0 [ 28.516364] Stack: [ 28.518509] ffff8801b6eb0000 ffff8801b54d8a00 ffff8801b6eb03d0 ffff8801b6eb02d8 [ 28.526526] ffff8801b54efce8 ffffffff836ca2b2 ffff8801b6eb0440 ffff8801b6eb0000 [ 28.534547] ffffffff836ca1e0 ffff8801b54efd20 ffffffff830260f5 ffff8801b6eb0440 [ 28.542669] Call Trace: [ 28.545250] [] pppol2tp_session_destruct+0xd2/0x110 [ 28.551899] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 28.558199] [] __sk_destruct+0x55/0x590 [ 28.563805] [] ? sock_release+0x1c0/0x1c0 [ 28.569582] [] sk_destruct+0x63/0x80 [ 28.574928] [] __sk_free+0x4f/0x220 [ 28.580184] [] sk_free+0x2b/0x40 [ 28.585184] [] pppol2tp_release+0x239/0x2e0 [ 28.591139] [] sock_release+0x96/0x1c0 [ 28.596656] [] sock_close+0x16/0x20 [ 28.601914] [] __fput+0x263/0x700 [ 28.606999] [] ____fput+0x15/0x20 [ 28.612084] [] task_work_run+0x10c/0x180 [ 28.617824] [] exit_to_usermode_loop+0xfc/0x120 [ 28.624125] [] do_syscall_64+0x364/0x490 [ 28.629820] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 28.636823] 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 15 de c9 fd 4c 89 ea 48 b8 00 [ 28.664191] RIP [] l2tp_session_free+0x11c/0x200 [ 28.670699] RSP [ 28.674347] CR2: 0000000000000080 [ 28.678243] ---[ end trace 47125ad6dbb4d87d ]--- [ 28.682995] Kernel panic - not syncing: Fatal exception [ 28.688664] Dumping ftrace buffer: [ 28.692188] (ftrace buffer empty) [ 28.695879] Kernel Offset: disabled [ 28.699488] Rebooting in 86400 seconds..