[....] Starting enhanced syslogd: rsyslogd[ 12.153962] audit: type=1400 audit(1518443810.040:4): avc: denied { syslog } for pid=3646 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 '10.128.0.17' (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 syzkaller login: [ 33.891589] ================================================================== [ 33.898970] BUG: KASAN: use-after-free in pppol2tp_release+0x293/0x2e0 [ 33.905604] Read of size 4 at addr ffff8801bf7be280 by task syzkaller117096/3812 [ 33.913101] [ 33.914699] CPU: 1 PID: 3812 Comm: syzkaller117096 Not tainted 4.9.80-g8a174b47 #31 [ 33.922458] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 33.931780] ffff8801d70d7d18 ffffffff81d94be9 ffffea0006fdef80 ffff8801bf7be280 [ 33.939747] 0000000000000000 ffff8801bf7be280 ffffffff82ed49f0 ffff8801d70d7d50 [ 33.947705] ffffffff8153e113 ffff8801bf7be280 0000000000000004 0000000000000000 [ 33.955683] Call Trace: [ 33.958241] [] dump_stack+0xc1/0x128 [ 33.963576] [] ? sock_release+0x1e0/0x1e0 [ 33.969347] [] print_address_description+0x73/0x280 [ 33.975997] [] ? sock_release+0x1e0/0x1e0 [ 33.981762] [] kasan_report+0x275/0x360 [ 33.987358] [] ? pppol2tp_release+0x293/0x2e0 [ 33.993470] [] __asan_report_load4_noabort+0x14/0x20 [ 34.000192] [] pppol2tp_release+0x293/0x2e0 [ 34.006132] [] sock_release+0x8d/0x1e0 [ 34.011660] [] sock_close+0x16/0x20 [ 34.017268] [] __fput+0x28c/0x6e0 [ 34.022349] [] ____fput+0x15/0x20 [ 34.027421] [] task_work_run+0x115/0x190 [ 34.033103] [] exit_to_usermode_loop+0xfc/0x120 [ 34.039392] [] syscall_return_slowpath+0x1a0/0x1e0 [ 34.045942] [] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 34.052488] [ 34.054087] Allocated by task 3812: [ 34.057682] save_stack_trace+0x16/0x20 [ 34.061624] save_stack+0x43/0xd0 [ 34.065043] kasan_kmalloc+0xad/0xe0 [ 34.068724] __kmalloc+0x11d/0x310 [ 34.072233] l2tp_session_create+0x38/0x1770 [ 34.076611] pppol2tp_connect+0x10fe/0x18f0 [ 34.080901] SYSC_connect+0x1b6/0x310 [ 34.084669] SyS_connect+0x24/0x30 [ 34.088178] entry_SYSCALL_64_fastpath+0x29/0xe8 [ 34.092900] [ 34.094505] Freed by task 3813: [ 34.097752] save_stack_trace+0x16/0x20 [ 34.101694] save_stack+0x43/0xd0 [ 34.105112] kasan_slab_free+0x72/0xc0 [ 34.108969] kfree+0x103/0x300 [ 34.112132] l2tp_session_free+0x166/0x200 [ 34.116335] l2tp_tunnel_closeall+0x26c/0x3a0 [ 34.120799] l2tp_udp_encap_destroy+0x87/0xe0 [ 34.125284] udpv6_destroy_sock+0xb1/0xd0 [ 34.129404] sk_common_release+0x6b/0x2f0 [ 34.133523] udp_lib_close+0x15/0x20 [ 34.137208] inet_release+0xfa/0x1d0 [ 34.140893] inet6_release+0x50/0x70 [ 34.144575] sock_release+0x8d/0x1e0 [ 34.148259] sock_close+0x16/0x20 [ 34.151679] __fput+0x28c/0x6e0 [ 34.154924] ____fput+0x15/0x20 [ 34.158174] task_work_run+0x115/0x190 [ 34.162029] exit_to_usermode_loop+0xfc/0x120 [ 34.166496] syscall_return_slowpath+0x1a0/0x1e0 [ 34.171220] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 34.175940] [ 34.177537] The buggy address belongs to the object at ffff8801bf7be280 [ 34.177537] which belongs to the cache kmalloc-512 of size 512 [ 34.190161] The buggy address is located 0 bytes inside of [ 34.190161] 512-byte region [ffff8801bf7be280, ffff8801bf7be480) [ 34.202203] The buggy address belongs to the page: [ 34.207105] page:ffffea0006fdef80 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 34.217268] flags: 0x8000000000004080(slab|head) [ 34.221990] page dumped because: kasan: bad access detected [ 34.227666] [ 34.229261] Memory state around the buggy address: [ 34.234159] ffff8801bf7be180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.241484] ffff8801bf7be200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 34.248987] >ffff8801bf7be280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.256314] ^ [ 34.259649] ffff8801bf7be300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.266975] ffff8801bf7be380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.274302] ================================================================== [ 34.281624] Disabling lock debugging due to kernel taint [ 34.287704] Kernel panic - not syncing: panic_on_warn set ... [ 34.287704] [ 34.295072] CPU: 0 PID: 3812 Comm: syzkaller117096 Tainted: G B 4.9.80-g8a174b47 #31 [ 34.304052] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 34.313380] ffff8801d70d7c70 ffffffff81d94be9 ffffffff841970c7 ffff8801d70d7d48 [ 34.321353] 0000000000000000 ffff8801bf7be280 ffffffff82ed49f0 ffff8801d70d7d38 [ 34.329322] ffffffff8142f5c1 0000000041b58ab3 ffffffff8418ab38 ffffffff8142f405 [ 34.337300] Call Trace: [ 34.339861] [] dump_stack+0xc1/0x128 [ 34.345196] [] ? sock_release+0x1e0/0x1e0 [ 34.350973] [] panic+0x1bc/0x3a8 [ 34.355959] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 34.364158] [] ? preempt_schedule+0x25/0x30 [ 34.370641] [] ? ___preempt_schedule+0x16/0x18 [ 34.376937] [] kasan_end_report+0x50/0x50 [ 34.382713] [] kasan_report+0x167/0x360 [ 34.388311] [] ? pppol2tp_release+0x293/0x2e0 [ 34.394428] [] __asan_report_load4_noabort+0x14/0x20 [ 34.401149] [] pppol2tp_release+0x293/0x2e0 [ 34.407092] [] sock_release+0x8d/0x1e0 [ 34.412596] [] sock_close+0x16/0x20 [ 34.417844] [] __fput+0x28c/0x6e0 [ 34.422924] [] ____fput+0x15/0x20 [ 34.427998] [] task_work_run+0x115/0x190 [ 34.433678] [] exit_to_usermode_loop+0xfc/0x120 [ 34.439968] [] syscall_return_slowpath+0x1a0/0x1e0 [ 34.446517] [] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 34.453439] Dumping ftrace buffer: [ 34.456948] (ftrace buffer empty) [ 34.460630] Kernel Offset: disabled [ 34.464227] Rebooting in 86400 seconds..