[....] 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[ 13.381996] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 16.373694] random: sshd: uninitialized urandom read (32 bytes read) [ 16.700632] random: sshd: uninitialized urandom read (32 bytes read) [ 17.239986] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.29' (ECDSA) to the list of known hosts. [ 22.983689] urandom_read: 1 callbacks suppressed [ 22.983692] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 23.202524] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 23.210875] IP: [] l2tp_session_free+0x11c/0x200 [ 23.217305] PGD 1ca2d8067 [ 23.219957] PUD 1bafd4067 PMD 0 [ 23.223439] [ 23.225069] Oops: 0002 [#1] PREEMPT SMP KASAN [ 23.229549] Dumping ftrace buffer: [ 23.233090] (ftrace buffer empty) [ 23.236775] Modules linked in: [ 23.240063] CPU: 1 PID: 3798 Comm: syz-executor760 Not tainted 4.9.122-g54068d6 #26 [ 23.247831] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 23.257162] task: ffff8801b8930000 task.stack: ffff8801b5cd0000 [ 23.263192] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 23.272097] RSP: 0018:ffff8801b5cd7ca0 EFLAGS: 00010246 [ 23.277528] RAX: dffffc0000000000 RBX: ffff8801b6293180 RCX: 0000000000000000 [ 23.284794] RDX: 1ffff10036df33a0 RSI: ffffffff836c39a1 RDI: ffff8801b6f99d00 [ 23.292049] RBP: ffff8801b5cd7cc0 R08: ffff8801b89308e8 R09: 0000000000000000 [ 23.299293] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6f99b80 [ 23.306684] R13: ffff8801b6293188 R14: 0000000000000000 R15: ffffffff83019be0 [ 23.313931] FS: 0000000000a74880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 23.322131] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 23.327990] CR2: 0000000000000080 CR3: 00000001c2ece000 CR4: 00000000001606f0 [ 23.335236] Stack: [ 23.337363] ffff8801c3c8d500 ffff8801b6293180 ffff8801c3c8d8d0 ffff8801c3c8d7d8 [ 23.345386] ffff8801b5cd7ce8 ffffffff836cb2b2 ffff8801c3c8d940 ffff8801c3c8d500 [ 23.353429] ffffffff836cb1e0 ffff8801b5cd7d20 ffffffff830270f5 ffff8801c3c8d940 [ 23.361444] Call Trace: [ 23.364016] [] pppol2tp_session_destruct+0xd2/0x110 [ 23.370740] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 23.377083] [] __sk_destruct+0x55/0x590 [ 23.382693] [] ? sock_release+0x1c0/0x1c0 [ 23.388470] [] sk_destruct+0x63/0x80 [ 23.393811] [] __sk_free+0x4f/0x220 [ 23.399065] [] sk_free+0x2b/0x40 [ 23.404059] [] pppol2tp_release+0x239/0x2e0 [ 23.410006] [] sock_release+0x96/0x1c0 [ 23.415522] [] sock_close+0x16/0x20 [ 23.420779] [] __fput+0x263/0x700 [ 23.425867] [] ____fput+0x15/0x20 [ 23.431014] [] task_work_run+0x10c/0x180 [ 23.436828] [] exit_to_usermode_loop+0xfc/0x120 [ 23.443130] [] do_syscall_64+0x364/0x490 [ 23.448821] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.455723] 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 95 d3 c9 fd 4c 89 ea 48 b8 00 [ 23.482772] RIP [] l2tp_session_free+0x11c/0x200 [ 23.489284] RSP [ 23.492896] CR2: 0000000000000080 [ 23.496494] ---[ end trace 0e81d490e2cd571d ]--- [ 23.501250] Kernel panic - not syncing: Fatal exception [ 23.506909] Dumping ftrace buffer: [ 23.510435] (ftrace buffer empty) [ 23.514123] Kernel Offset: disabled [ 23.517723] Rebooting in 86400 seconds..