[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.380695] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 19.210495] random: sshd: uninitialized urandom read (32 bytes read) [ 19.567004] random: sshd: uninitialized urandom read (32 bytes read) [ 20.579932] random: sshd: uninitialized urandom read (32 bytes read) [ 20.706429] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.43' (ECDSA) to the list of known hosts. [ 26.210790] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 26.446952] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 26.455194] IP: [] l2tp_session_free+0x11c/0x200 [ 26.461612] PGD 1bb572067 [ 26.464254] PUD 1c3eeb067 PMD 0 [ 26.467735] [ 26.469355] Oops: 0002 [#1] PREEMPT SMP KASAN [ 26.473866] Dumping ftrace buffer: [ 26.477377] (ftrace buffer empty) [ 26.481064] Modules linked in: [ 26.484388] CPU: 1 PID: 3795 Comm: syz-executor588 Not tainted 4.9.113-g47bbcd6 #62 [ 26.492183] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.501523] task: ffff8801b9133000 task.stack: ffff8801d8cf0000 [ 26.507553] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 26.516437] RSP: 0018:ffff8801d8cf7ca0 EFLAGS: 00010246 [ 26.521858] RAX: dffffc0000000000 RBX: ffff8801ca2dcf00 RCX: 0000000000000000 [ 26.529104] RDX: 1ffff100370a4ab0 RSI: ffffffff836bcce1 RDI: ffff8801b8525580 [ 26.536347] RBP: ffff8801d8cf7cc0 R08: ffff8801b91338e8 R09: 0000000000000000 [ 26.543598] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b8525400 [ 26.550846] R13: ffff8801ca2dcf08 R14: 0000000000000000 R15: ffffffff83013be0 [ 26.558092] FS: 00000000007ef880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 26.566289] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 26.572150] CR2: 0000000000000080 CR3: 00000001bc9c7000 CR4: 00000000001606f0 [ 26.579394] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 26.586638] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 26.593900] Stack: [ 26.596024] ffff8801c8361980 ffff8801ca2dcf00 ffff8801c8361d50 ffff8801c8361c58 [ 26.604041] ffff8801d8cf7ce8 ffffffff836c45f2 ffff8801c8361dc0 ffff8801c8361980 [ 26.612026] ffffffff836c4520 ffff8801d8cf7d20 ffffffff83021095 ffff8801c8361dc0 [ 26.620011] Call Trace: [ 26.623186] [] pppol2tp_session_destruct+0xd2/0x110 [ 26.629824] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 26.636116] [] __sk_destruct+0x55/0x590 [ 26.641711] [] ? sock_release+0x1c0/0x1c0 [ 26.647478] [] sk_destruct+0x63/0x80 [ 26.652820] [] __sk_free+0x4f/0x220 [ 26.658070] [] sk_free+0x2b/0x40 [ 26.663060] [] pppol2tp_release+0x239/0x2e0 [ 26.669011] [] sock_release+0x96/0x1c0 [ 26.674521] [] sock_close+0x16/0x20 [ 26.679773] [] __fput+0x263/0x700 [ 26.684849] [] ____fput+0x15/0x20 [ 26.689927] [] task_work_run+0x10c/0x180 [ 26.695614] [] exit_to_usermode_loop+0xfc/0x120 [ 26.701913] [] do_syscall_64+0x364/0x490 [ 26.707595] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 26.714486] 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 55 1d ca fd 4c 89 ea 48 b8 00 [ 26.741323] RIP [] l2tp_session_free+0x11c/0x200 [ 26.747833] RSP [ 26.751443] CR2: 0000000000000080 [ 26.754944] ---[ end trace 33aed7eaafc7d5f5 ]--- [ 26.759700] Kernel panic - not syncing: Fatal exception [ 26.765078] Dumping ftrace buffer: [ 26.768589] (ftrace buffer empty) [ 26.772271] Kernel Offset: disabled [ 26.775868] Rebooting in 86400 seconds..