[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.395048] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 22.782212] random: sshd: uninitialized urandom read (32 bytes read, 38 bits of entropy available) [ 23.233641] random: sshd: uninitialized urandom read (32 bytes read, 38 bits of entropy available) [ 24.166889] random: nonblocking pool is initialized Warning: Permanently added '10.128.0.41' (ECDSA) to the list of known hosts. [ 30.608685] IPVS: Creating netns size=2552 id=1 executing program [ 30.709862] ================================================================== [ 30.717251] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 30.724501] Read of size 4 at addr ffff8801d8c24000 by task syz-executor821/3854 [ 30.732002] [ 30.733605] CPU: 0 PID: 3854 Comm: syz-executor821 Not tainted 4.4.138-g07c0138 #62 [ 30.741366] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 30.750694] 0000000000000000 23cfd72a4ec0bf22 ffff8801c670fcc0 ffffffff81e0ed0d [ 30.758691] ffffea0007630900 ffff8801d8c24000 0000000000000000 ffff8801d8c24000 [ 30.766668] ffffffff82f1a2b0 ffff8801c670fcf8 ffffffff81515a16 ffff8801d8c24000 [ 30.774671] Call Trace: [ 30.777231] [] dump_stack+0xc1/0x124 [ 30.782578] [] ? sock_release+0x1c0/0x1c0 [ 30.788353] [] print_address_description+0x6c/0x216 [ 30.794988] [] ? sock_release+0x1c0/0x1c0 [ 30.800758] [] kasan_report.cold.7+0x175/0x2f7 [ 30.806970] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 30.813696] [] __asan_report_load4_noabort+0x14/0x20 [ 30.820421] [] l2tp_session_queue_purge+0xf4/0x100 [ 30.826986] [] ? sock_release+0x1c0/0x1c0 [ 30.832758] [] pppol2tp_release+0x1ff/0x310 [ 30.838702] [] sock_release+0x96/0x1c0 [ 30.844210] [] sock_close+0x16/0x20 [ 30.849462] [] __fput+0x235/0x6f0 [ 30.854551] [] ____fput+0x15/0x20 [ 30.859626] [] task_work_run+0x10f/0x190 [ 30.865308] [] exit_to_usermode_loop+0x13d/0x160 [ 30.871698] [] syscall_return_slowpath+0x1b5/0x1f0 [ 30.878257] [] int_ret_from_sys_call+0x25/0xa3 [ 30.884467] [ 30.886074] Allocated by task 3853: [ 30.889672] [] save_stack_trace+0x26/0x50 [ 30.895566] [] save_stack+0x43/0xd0 [ 30.900949] [] kasan_kmalloc+0xc7/0xe0 [ 30.906577] [] __kmalloc+0x124/0x310 [ 30.912043] [] l2tp_session_create+0x39/0x1030 [ 30.918367] [] pppol2tp_connect+0x10f0/0x1910 [ 30.924604] [] SYSC_connect+0x1b8/0x300 [ 30.930318] [] SyS_connect+0x24/0x30 [ 30.935781] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 30.942450] [ 30.944049] Freed by task 3853: [ 30.947294] [] save_stack_trace+0x26/0x50 [ 30.953194] [] save_stack+0x43/0xd0 [ 30.958578] [] kasan_slab_free+0x72/0xc0 [ 30.964388] [] kfree+0xf4/0x310 [ 30.969416] [] l2tp_session_free+0x170/0x200 [ 30.975562] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 30.981976] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 30.988379] [] udp_destroy_sock+0x118/0x1a0 [ 30.994442] [] sk_common_release+0x6d/0x300 [ 31.000500] [] udp_lib_close+0x15/0x20 [ 31.006130] [] inet_release+0xff/0x1d0 [ 31.011765] [] sock_release+0x96/0x1c0 [ 31.017399] [] sock_close+0x16/0x20 [ 31.022772] [] __fput+0x235/0x6f0 [ 31.027962] [] ____fput+0x15/0x20 [ 31.033154] [] task_work_run+0x10f/0x190 [ 31.038952] [] exit_to_usermode_loop+0x13d/0x160 [ 31.045454] [] syscall_return_slowpath+0x1b5/0x1f0 [ 31.052119] [] int_ret_from_sys_call+0x25/0xa3 [ 31.058451] [ 31.060052] The buggy address belongs to the object at ffff8801d8c24000 [ 31.060052] which belongs to the cache kmalloc-512 of size 512 [ 31.072677] The buggy address is located 0 bytes inside of [ 31.072677] 512-byte region [ffff8801d8c24000, ffff8801d8c24200) [ 31.084464] The buggy address belongs to the page: [ 32.479620] PANIC: double fault, error_code: 0x0 [ 32.484390] CPU: 0 PID: 3854 Comm: syz-executor821 Not tainted 4.4.138-g07c0138 #62 [ 32.492164] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.501493] task: ffff8801d8db8000 task.stack: ffff8801c6708000 [ 32.507522] RIP: 0010:[] [] dump_page_badflags+0x12/0x70 [ 32.516297] RSP: 0018:ffff880100000000 EFLAGS: 00010046 [ 32.521719] RAX: ffff8801d8db8000 RBX: ffffea0007630900 RCX: 0000000000000000 [ 32.528963] RDX: 0000000000000000 RSI: ffffffff83aa9de0 RDI: ffffea0007630900 [ 32.536206] RBP: ffff880100000020 R08: 0000000000000001 R09: 0000000000000000 [ 32.543448] R10: 0000000000000001 R11: ffffffff858ed0f4 R12: 0000000000000000 [ 32.550694] R13: ffffffff83aa9de0 R14: ffff8801d8c24000 R15: ffff8801d8c24200 [ 32.557937] FS: 00007f87bf1cd700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 32.566135] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 32.571988] CR2: ffff8800fffffff8 CR3: 00000001c9950000 CR4: 00000000001606f0 [ 32.579236] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 32.586477] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 32.593717] Stack: [ 32.595835] [ 32.597434] Call Trace: [ 32.599998] [ 32.602029] Code: 42 9f 84 5b 5d c3 48 89 df e8 fb c8 06 00 eb dd 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 49 89 f5 41 54 49 89 d4 <53> 48 89 fb 48 83 ec 08 e8 71 45 ec ff 48 89 da 48 b8 00 00 00 [ 32.629104] Kernel panic - not syncing: Machine halted. [ 32.634440] CPU: 0 PID: 3854 Comm: syz-executor821 Not tainted 4.4.138-g07c0138 #62 [ 32.642209] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.651537] 0000000000000000 23cfd72a4ec0bf22 ffff8801db20ce40 ffffffff81e0ed0d [ 32.659515] ffffffff83a375c0 0000000000000000 ffffffff83a08060 ffff880100000000 [ 32.667503] ffff8801d8c24200 ffff8801db20cf00 ffffffff8140a184 0000000041b58ab3 [ 32.675485] Call Trace: [ 32.678043] <#DF> [] dump_stack+0xc1/0x124 [ 32.684120] [] panic+0x19e/0x38d [ 32.689106] [] ? add_taint.cold.4+0x16/0x16 [ 32.695050] [] ? vprintk_emit+0x249/0x840 [ 32.700816] [] ? vprintk_emit+0x249/0x840 [ 32.706585] [] df_debug+0x2d/0x2d [ 32.711660] [] do_double_fault+0x113/0x230 [ 32.717522] [] double_fault+0x2d/0x40 [ 32.722944] [] ? dump_page_badflags+0x12/0x70 [ 32.729056] <> [ 32.732531] Dumping ftrace buffer: [ 32.736383] (ftrace buffer empty) [ 32.740063] Kernel Offset: disabled [ 32.743679] Rebooting in 86400 seconds..