[....] 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[ 19.217045] random: sshd: uninitialized urandom read (32 bytes read, 31 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 22.965390] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) [ 23.319722] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) [ 24.394685] random: nonblocking pool is initialized Warning: Permanently added '10.128.10.47' (ECDSA) to the list of known hosts. executing program [ 30.247384] ================================================================== [ 30.254788] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 30.262035] Read of size 4 at addr ffff8801d098a500 by task syz-executor135/3704 [ 30.269548] [ 30.271151] CPU: 0 PID: 3704 Comm: syz-executor135 Not tainted 4.4.135-ge75204c #55 [ 30.278913] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 30.288241] 0000000000000000 7888d6a6395578bf ffff8801cd217cc0 ffffffff81e0ed0d [ 30.296227] ffffea0007426280 ffff8801d098a500 0000000000000000 ffff8801d098a500 [ 30.304213] ffffffff82f1a1e0 ffff8801cd217cf8 ffffffff81515946 ffff8801d098a500 [ 30.312516] Call Trace: [ 30.315078] [] dump_stack+0xc1/0x124 [ 30.320416] [] ? sock_release+0x1c0/0x1c0 [ 30.326197] [] print_address_description+0x6c/0x216 [ 30.332834] [] ? sock_release+0x1c0/0x1c0 [ 30.338603] [] kasan_report.cold.7+0x175/0x2f7 [ 30.344806] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 30.351531] [] __asan_report_load4_noabort+0x14/0x20 [ 30.358252] [] l2tp_session_queue_purge+0xf4/0x100 [ 30.364800] [] ? sock_release+0x1c0/0x1c0 [ 30.370567] [] pppol2tp_release+0x1ff/0x310 [ 30.376509] [] sock_release+0x96/0x1c0 [ 30.382026] [] sock_close+0x16/0x20 [ 30.387285] [] __fput+0x235/0x6f0 [ 30.392367] [] ____fput+0x15/0x20 [ 30.397442] [] task_work_run+0x10f/0x190 [ 30.403126] [] exit_to_usermode_loop+0x13d/0x160 [ 30.409504] [] syscall_return_slowpath+0x1b5/0x1f0 [ 30.416056] [] int_ret_from_sys_call+0x25/0xa3 [ 30.422256] [ 30.423857] Allocated by task 3703: [ 30.427462] [] save_stack_trace+0x26/0x50 [ 30.433356] [] save_stack+0x43/0xd0 [ 30.438723] [] kasan_kmalloc+0xc7/0xe0 [ 30.444353] [] __kmalloc+0x124/0x310 [ 30.449806] [] l2tp_session_create+0x39/0x1030 [ 30.456138] [] pppol2tp_connect+0x10f0/0x1910 [ 30.462372] [] SYSC_connect+0x1b8/0x300 [ 30.468083] [] SyS_connect+0x24/0x30 [ 30.473535] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 30.480203] [ 30.481800] Freed by task 3703: [ 30.485048] [] save_stack_trace+0x26/0x50 [ 30.490942] [] save_stack+0x43/0xd0 [ 30.496307] [] kasan_slab_free+0x72/0xc0 [ 30.502106] [] kfree+0xf4/0x310 [ 30.507125] [] l2tp_session_free+0x170/0x200 [ 30.513282] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 30.519700] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 30.526108] [] udp_destroy_sock+0x118/0x1a0 [ 30.532181] [] sk_common_release+0x6d/0x300 [ 30.538239] [] udp_lib_close+0x15/0x20 [ 30.543862] [] inet_release+0xff/0x1d0 [ 30.549497] [] sock_release+0x96/0x1c0 [ 30.555123] [] sock_close+0x16/0x20 [ 30.560486] [] __fput+0x235/0x6f0 [ 30.565679] [] ____fput+0x15/0x20 [ 30.570876] [] task_work_run+0x10f/0x190 [ 30.576675] [] exit_to_usermode_loop+0x13d/0x160 [ 30.583170] [] syscall_return_slowpath+0x1b5/0x1f0 [ 30.589846] [] int_ret_from_sys_call+0x25/0xa3 [ 30.596167] [ 30.597768] The buggy address belongs to the object at ffff8801d098a500 [ 30.597768] which belongs to the cache kmalloc-512 of size 512 [ 30.610395] The buggy address is located 0 bytes inside of [ 30.610395] 512-byte region [ffff8801d098a500, ffff8801d098a700) [ 30.622064] The buggy address belongs to the page: [ 32.059337] PANIC: double fault, error_code: 0x0 [ 32.064119] CPU: 0 PID: 3704 Comm: syz-executor135 Not tainted 4.4.135-ge75204c #55 [ 32.071883] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.081209] task: ffff8800b1b81800 task.stack: ffff8801cd210000 [ 32.087237] RIP: 0010:[] [] dump_page_badflags+0x12/0x70 [ 32.095995] RSP: 0018:ffff880100000000 EFLAGS: 00010046 [ 32.101414] RAX: ffff8800b1b81800 RBX: ffffea0007426280 RCX: 0000000000000000 [ 32.108655] RDX: 0000000000000000 RSI: ffffffff83aa9ee0 RDI: ffffea0007426280 [ 32.115895] RBP: ffff880100000020 R08: 0000000000000001 R09: 0000000000000000 [ 32.123137] R10: 0000000000000001 R11: ffffffff858ed134 R12: 0000000000000000 [ 32.130377] R13: ffffffff83aa9ee0 R14: ffff8801d098a500 R15: ffff8801d098a700 [ 32.137618] FS: 00007f318ca7c700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 32.145813] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 32.151664] CR2: ffff8800fffffff8 CR3: 00000001cd973000 CR4: 00000000001606f0 [ 32.158918] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 32.166168] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 32.173406] Stack: [ 32.175525] [ 32.177122] Call Trace: [ 32.179683] [ 32.181715] Code: 41 9f 84 5b 5d c3 48 89 df e8 9b 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 e1 45 ec ff 48 89 da 48 b8 00 00 00 [ 32.208912] Kernel panic - not syncing: Machine halted. [ 32.214251] CPU: 0 PID: 3704 Comm: syz-executor135 Not tainted 4.4.135-ge75204c #55 [ 32.222014] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.231337] 0000000000000000 7888d6a6395578bf ffff8801db20ce40 ffffffff81e0ed0d [ 32.239313] ffffffff83a376e0 0000000000000000 ffffffff83a08060 ffff880100000000 [ 32.247285] ffff8801d098a700 ffff8801db20cf00 ffffffff8140a104 0000000041b58ab3 [ 32.255268] Call Trace: [ 32.257822] <#DF> [] dump_stack+0xc1/0x124 [ 32.263892] [] panic+0x19e/0x38d [ 32.268891] [] ? add_taint.cold.4+0x16/0x16 [ 32.274833] [] ? vprintk_emit+0x249/0x840 [ 32.280601] [] ? vprintk_emit+0x249/0x840 [ 32.286371] [] df_debug+0x2d/0x2d [ 32.291447] [] do_double_fault+0x113/0x230 [ 32.297304] [] double_fault+0x2d/0x40 [ 32.302726] [] ? dump_page_badflags+0x12/0x70 [ 32.308837] <> [ 32.312488] Dumping ftrace buffer: [ 32.316344] (ftrace buffer empty) [ 32.320025] Kernel Offset: disabled [ 32.323636] Rebooting in 86400 seconds..