[....] Starting enhanced syslogd: rsyslogd[ 10.787031] audit: type=1400 audit(1516598128.520:4): avc: denied { syslog } for pid=3176 comm="rsyslogd" capability=34 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=capability2 permissive=1 [?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.4' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 25.143874] ================================================================== [ 25.144932] BUG: KASAN: use-after-free in do_raw_spin_lock+0x1ac/0x1e0 [ 25.145842] Read of size 4 at addr ffff8801cbc5b95c by task syzkaller651506/3386 [ 25.146846] [ 25.147109] CPU: 1 PID: 3386 Comm: syzkaller651506 Not tainted 4.9.77-ge12a9c4 #18 [ 25.148136] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.149388] ffff8801c7da7c50 ffffffff81d941c9 ffffea00072f1680 ffff8801cbc5b95c [ 25.150575] 0000000000000000 ffff8801cbc5b95c ffff8801cbc5ba80 ffff8801c7da7c88 [ 25.151730] ffffffff8153db93 ffff8801cbc5b95c 0000000000000004 0000000000000000 [ 25.153108] Call Trace: [ 25.153528] [] dump_stack+0xc1/0x128 [ 25.154316] [] print_address_description+0x73/0x280 [ 25.155224] [] kasan_report+0x275/0x360 [ 25.156028] [] ? do_raw_spin_lock+0x1ac/0x1e0 [ 25.156861] [] __asan_report_load4_noabort+0x14/0x20 [ 25.157767] [] do_raw_spin_lock+0x1ac/0x1e0 [ 25.158614] [] _raw_spin_lock_irqsave+0x56/0x70 [ 25.159506] [] ? skb_dequeue+0x22/0x180 [ 25.160262] [] skb_dequeue+0x22/0x180 [ 25.160996] [] l2tp_session_queue_purge+0xab/0x100 [ 25.161887] [] ? sock_release+0x1e0/0x1e0 [ 25.162673] [] pppol2tp_release+0x1ff/0x2e0 [ 25.163477] [] sock_release+0x8d/0x1e0 [ 25.164296] [] sock_close+0x16/0x20 [ 25.169544] [] __fput+0x28c/0x6e0 [ 25.174615] [] ____fput+0x15/0x20 [ 25.179687] [] task_work_run+0x115/0x190 [ 25.185379] [] exit_to_usermode_loop+0xfc/0x120 [ 25.191671] [] syscall_return_slowpath+0x1a0/0x1e0 [ 25.198226] [] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 25.204775] [ 25.206373] Allocated by task 3386: [ 25.209978] save_stack_trace+0x16/0x20 [ 25.213924] save_stack+0x43/0xd0 [ 25.217345] kasan_kmalloc+0xad/0xe0 [ 25.221027] __kmalloc+0x11d/0x310 [ 25.224536] l2tp_session_create+0x38/0x1770 [ 25.228911] pppol2tp_connect+0x10fe/0x18f0 [ 25.233216] SYSC_connect+0x1b6/0x310 [ 25.236988] SyS_connect+0x24/0x30 [ 25.240510] entry_SYSCALL_64_fastpath+0x29/0xe8 [ 25.245232] [ 25.246832] Freed by task 3387: [ 25.250078] save_stack_trace+0x16/0x20 [ 25.254022] save_stack+0x43/0xd0 [ 25.257448] kasan_slab_free+0x72/0xc0 [ 25.261303] kfree+0x103/0x300 [ 25.264467] l2tp_session_free+0x166/0x200 [ 25.268669] l2tp_tunnel_closeall+0x26c/0x3a0 [ 25.273134] l2tp_udp_encap_destroy+0x87/0xe0 [ 25.277599] udpv6_destroy_sock+0xb1/0xd0 [ 25.281724] sk_common_release+0x6b/0x2f0 [ 25.285841] udp_lib_close+0x15/0x20 [ 25.289523] inet_release+0xfa/0x1d0 [ 25.293214] inet6_release+0x50/0x70 [ 25.296900] sock_release+0x8d/0x1e0 [ 25.300585] sock_close+0x16/0x20 [ 25.304008] __fput+0x28c/0x6e0 [ 25.307257] ____fput+0x15/0x20 [ 25.310505] task_work_run+0x115/0x190 [ 25.314361] exit_to_usermode_loop+0xfc/0x120 [ 25.318835] syscall_return_slowpath+0x1a0/0x1e0 [ 25.323562] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 25.328285] [ 25.329887] The buggy address belongs to the object at ffff8801cbc5b900 [ 25.329887] which belongs to the cache kmalloc-512 of size 512 [ 25.342511] The buggy address is located 92 bytes inside of [ 25.342511] 512-byte region [ffff8801cbc5b900, ffff8801cbc5bb00) [ 25.354269] The buggy address belongs to the page: [ 25.359171] page:ffffea00072f1680 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 25.369339] flags: 0x8000000000004080(slab|head) [ 25.374069] page dumped because: kasan: bad access detected [ 25.379752] [ 25.381348] Memory state around the buggy address: [ 25.386245] ffff8801cbc5b800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.393582] ffff8801cbc5b880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 25.400911] >ffff8801cbc5b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.408239] ^ [ 25.414440] ffff8801cbc5b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.421768] ffff8801cbc5ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.429354] ================================================================== [ 25.436682] Disabling lock debugging due to kernel taint [ 25.442100] Kernel panic - not syncing: panic_on_warn set ... [ 25.442100] [ 25.449432] CPU: 1 PID: 3386 Comm: syzkaller651506 Tainted: G B 4.9.77-ge12a9c4 #18 [ 25.458319] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.467646] ffff8801c7da7ba8 ffffffff81d941c9 ffffffff841970ff ffff8801c7da7c80 [ 25.475619] 0000000000000000 ffff8801cbc5b95c ffff8801cbc5ba80 ffff8801c7da7c70 [ 25.483584] ffffffff8142f3c1 0000000041b58ab3 ffffffff8418ab70 ffffffff8142f205 [ 25.491557] Call Trace: [ 25.494114] [] dump_stack+0xc1/0x128 [ 25.499452] [] panic+0x1bc/0x3a8 [ 25.504441] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 25.512639] [] kasan_end_report+0x50/0x50 [ 25.518408] [] kasan_report+0x167/0x360 [ 25.524002] [] ? do_raw_spin_lock+0x1ac/0x1e0 [ 25.530116] [] __asan_report_load4_noabort+0x14/0x20 [ 25.536846] [] do_raw_spin_lock+0x1ac/0x1e0 [ 25.542788] [] _raw_spin_lock_irqsave+0x56/0x70 [ 25.549077] [] ? skb_dequeue+0x22/0x180 [ 25.554672] [] skb_dequeue+0x22/0x180 [ 25.560094] [] l2tp_session_queue_purge+0xab/0x100 [ 25.566645] [] ? sock_release+0x1e0/0x1e0 [ 25.572415] [] pppol2tp_release+0x1ff/0x2e0 [ 25.578355] [] sock_release+0x8d/0x1e0 [ 25.583860] [] sock_close+0x16/0x20 [ 25.589105] [] __fput+0x28c/0x6e0 [ 25.594180] [] ____fput+0x15/0x20 [ 25.599254] [] task_work_run+0x115/0x190 [ 25.604941] [] exit_to_usermode_loop+0xfc/0x120 [ 25.611233] [] syscall_return_slowpath+0x1a0/0x1e0 [ 25.617782] [] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 25.624747] Dumping ftrace buffer: [ 25.628261] (ftrace buffer empty) [ 25.631942] Kernel Offset: disabled [ 25.635549] Rebooting in 86400 seconds..