[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.528962] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 20.617010] random: sshd: uninitialized urandom read (32 bytes read) [ 20.928637] random: sshd: uninitialized urandom read (32 bytes read) [ 21.422678] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.35' (ECDSA) to the list of known hosts. [ 27.212660] urandom_read: 1 callbacks suppressed [ 27.212664] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 27.414219] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 27.422451] IP: [] l2tp_session_free+0x11c/0x200 [ 27.428895] PGD 1cacb1067 [ 27.431540] PUD 1cad16067 PMD 0 [ 27.435030] [ 27.436663] Oops: 0002 [#1] PREEMPT SMP KASAN [ 27.441135] Dumping ftrace buffer: [ 27.444702] (ftrace buffer empty) [ 27.448394] Modules linked in: [ 27.451686] CPU: 0 PID: 3793 Comm: syz-executor179 Not tainted 4.9.121-g681e57b #77 [ 27.459453] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.468785] task: ffff8801b9538000 task.stack: ffff8801d94d0000 [ 27.474877] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 27.483751] RSP: 0018:ffff8801d94d7ca0 EFLAGS: 00010246 [ 27.489172] RAX: dffffc0000000000 RBX: ffff8801b8ae8500 RCX: 0000000000000000 [ 27.496419] RDX: 1ffff10036fc57a0 RSI: ffffffff836c29a1 RDI: ffff8801b7e2bd00 [ 27.503664] RBP: ffff8801d94d7cc0 R08: ffff8801b95388e8 R09: 0000000000000000 [ 27.510912] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b7e2bb80 [ 27.518159] R13: ffff8801b8ae8508 R14: 0000000000000000 R15: ffffffff83018be0 [ 27.525405] FS: 00000000011a7880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 27.533605] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.539475] CR2: 0000000000000080 CR3: 00000001b7abf000 CR4: 00000000001606f0 [ 27.546730] Stack: [ 27.548884] ffff8801b7944c80 ffff8801b8ae8500 ffff8801b7945050 ffff8801b7944f58 [ 27.556900] ffff8801d94d7ce8 ffffffff836ca2b2 ffff8801b79450c0 ffff8801b7944c80 [ 27.564887] ffffffff836ca1e0 ffff8801d94d7d20 ffffffff830260f5 ffff8801b79450c0 [ 27.573016] Call Trace: [ 27.575589] [] pppol2tp_session_destruct+0xd2/0x110 [ 27.582239] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 27.588787] [] __sk_destruct+0x55/0x590 [ 27.594390] [] ? sock_release+0x1c0/0x1c0 [ 27.600320] [] sk_destruct+0x63/0x80 [ 27.605674] [] __sk_free+0x4f/0x220 [ 27.610933] [] sk_free+0x2b/0x40 [ 27.616134] [] pppol2tp_release+0x239/0x2e0 [ 27.622093] [] sock_release+0x96/0x1c0 [ 27.627612] [] sock_close+0x16/0x20 [ 27.632870] [] __fput+0x263/0x700 [ 27.638068] [] ____fput+0x15/0x20 [ 27.643152] [] task_work_run+0x10c/0x180 [ 27.648845] [] exit_to_usermode_loop+0xfc/0x120 [ 27.655147] [] do_syscall_64+0x364/0x490 [ 27.660843] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.667851] 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 65 df c9 fd 4c 89 ea 48 b8 00 [ 27.695073] RIP [] l2tp_session_free+0x11c/0x200 [ 27.701588] RSP [ 27.705193] CR2: 0000000000000080 [ 27.709100] ---[ end trace f9db2d33c86a7fa8 ]--- [ 27.713841] Kernel panic - not syncing: Fatal exception [ 27.719503] Dumping ftrace buffer: [ 27.723078] (ftrace buffer empty) [ 27.726775] Kernel Offset: disabled [ 27.730382] Rebooting in 86400 seconds..