[....] Starting enhanced syslogd: rsyslogd[ 11.122716] audit: type=1400 audit(1516140440.580:4): avc: denied { syslog } for pid=3171 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[1G[[32m ok [39;49m8[?25h[?0c. Starting mcstransd: [....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.15.192' (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 executing program executing program syzkaller login: [ 31.711274] ================================================================== [ 31.712412] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xe9/0x110 [ 31.713398] Read of size 4 at addr ffff8801cc0d3400 by task syzkaller614837/3331 [ 31.714491] [ 31.714722] CPU: 1 PID: 3331 Comm: syzkaller614837 Not tainted 4.9.76-g8dec074 #13 [ 31.715771] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 31.717013] ffff8801c25dfc60 ffffffff81d93169 ffffea0007303480 ffff8801cc0d3400 [ 31.718167] 0000000000000000 ffff8801cc0d3400 ffffffff82ed29f0 ffff8801c25dfc98 [ 31.719320] ffffffff8153cb43 ffff8801cc0d3400 0000000000000004 0000000000000000 [ 31.720460] Call Trace: [ 31.720814] [] dump_stack+0xc1/0x128 [ 31.721572] [] ? sock_release+0x1e0/0x1e0 [ 31.722356] [] print_address_description+0x73/0x280 [ 31.723241] [] ? sock_release+0x1e0/0x1e0 [ 31.724004] [] kasan_report+0x275/0x360 [ 31.724747] [] ? pppol2tp_session_destruct+0xe9/0x110 [ 31.725685] [] __asan_report_load4_noabort+0x14/0x20 [ 31.726611] [] pppol2tp_session_destruct+0xe9/0x110 [ 31.727506] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 31.728385] [] __sk_destruct+0x53/0x570 [ 31.729126] [] ? sock_release+0x1e0/0x1e0 [ 31.729899] [] sk_destruct+0x47/0x80 [ 31.730606] [] __sk_free+0x57/0x230 [ 31.731318] [] sk_free+0x23/0x30 [ 31.735863] [] pppol2tp_release+0x23d/0x2e0 [ 31.741798] [] sock_release+0x8d/0x1e0 [ 31.747299] [] sock_close+0x16/0x20 [ 31.752546] [] __fput+0x28c/0x6e0 [ 31.757615] [] ____fput+0x15/0x20 [ 31.762681] [] task_work_run+0x115/0x190 [ 31.768360] [] exit_to_usermode_loop+0xfc/0x120 [ 31.775252] [] syscall_return_slowpath+0x1a0/0x1e0 [ 31.781803] [] entry_SYSCALL_64_fastpath+0xe0/0xe2 [ 31.788344] [ 31.789940] Allocated by task 3330: [ 31.793534] save_stack_trace+0x16/0x20 [ 31.797472] save_stack+0x43/0xd0 [ 31.800899] kasan_kmalloc+0xad/0xe0 [ 31.804600] __kmalloc+0x11d/0x310 [ 31.804609] l2tp_session_create+0x38/0x1770 [ 31.804614] pppol2tp_connect+0x10fe/0x18f0 [ 31.804620] SYSC_connect+0x1b6/0x310 [ 31.804627] SyS_connect+0x24/0x30 [ 31.804633] entry_SYSCALL_64_fastpath+0x23/0xe2 [ 31.804635] [ 31.804637] Freed by task 3330: [ 31.804643] save_stack_trace+0x16/0x20 [ 31.804647] save_stack+0x43/0xd0 [ 31.804652] kasan_slab_free+0x72/0xc0 [ 31.804656] kfree+0x103/0x300 [ 31.804661] l2tp_session_free+0x166/0x200 [ 31.804666] l2tp_tunnel_closeall+0x26c/0x3a0 [ 31.804671] l2tp_udp_encap_destroy+0x87/0xe0 [ 31.804677] udpv6_destroy_sock+0xb1/0xd0 [ 31.804684] sk_common_release+0x6b/0x2f0 [ 31.804688] udp_lib_close+0x15/0x20 [ 31.804695] inet_release+0xfa/0x1d0 [ 31.804703] inet6_release+0x50/0x70 [ 31.804708] sock_release+0x8d/0x1e0 [ 31.804713] sock_close+0x16/0x20 [ 31.804720] __fput+0x28c/0x6e0 [ 31.804725] ____fput+0x15/0x20 [ 31.804730] task_work_run+0x115/0x190 [ 31.804736] exit_to_usermode_loop+0xfc/0x120 [ 31.804741] syscall_return_slowpath+0x1a0/0x1e0 [ 31.804746] entry_SYSCALL_64_fastpath+0xe0/0xe2 [ 31.804747] [ 31.804752] The buggy address belongs to the object at ffff8801cc0d3400 [ 31.804752] which belongs to the cache kmalloc-512 of size 512 [ 31.804761] The buggy address is located 0 bytes inside of [ 31.804761] 512-byte region [ffff8801cc0d3400, ffff8801cc0d3600) [ 31.804762] The buggy address belongs to the page: [ 31.804772] page:ffffea0007303480 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 31.804776] flags: 0x8000000000004080(slab|head) [ 31.804779] page dumped because: kasan: bad access detected [ 31.804780] [ 31.804781] Memory state around the buggy address: [ 31.804787] ffff8801cc0d3300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 31.804791] ffff8801cc0d3380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 31.804796] >ffff8801cc0d3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 31.804797] ^ [ 31.804802] ffff8801cc0d3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 31.804806] ffff8801cc0d3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 31.804808] ================================================================== [ 31.804810] Disabling lock debugging due to kernel taint [ 31.807643] Kernel panic - not syncing: panic_on_warn set ... [ 31.807643] [ 31.807652] CPU: 1 PID: 3331 Comm: syzkaller614837 Tainted: G B 4.9.76-g8dec074 #13 [ 31.807655] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 31.807666] ffff8801c25dfbb8 ffffffff81d93169 ffffffff84195c2f ffff8801c25dfc90 [ 31.807675] 0000000000000000 ffff8801cc0d3400 ffffffff82ed29f0 ffff8801c25dfc80 [ 31.807683] ffffffff8142e371 0000000041b58ab3 ffffffff84189690 ffffffff8142e1b5 [ 31.807685] Call Trace: [ 31.807695] [] dump_stack+0xc1/0x128 [ 31.807704] [] ? sock_release+0x1e0/0x1e0 [ 31.807713] [] panic+0x1bc/0x3a8 [ 31.807721] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 31.807730] [] ? preempt_schedule+0x25/0x30 [ 31.807736] [] ? ___preempt_schedule+0x16/0x18 [ 31.807744] [] kasan_end_report+0x50/0x50 [ 31.807751] [] kasan_report+0x167/0x360 [ 31.807763] [] ? pppol2tp_session_destruct+0xe9/0x110 [ 31.807770] [] __asan_report_load4_noabort+0x14/0x20 [ 31.807777] [] pppol2tp_session_destruct+0xe9/0x110 [ 31.807783] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 31.807791] [] __sk_destruct+0x53/0x570 [ 31.807797] [] ? sock_release+0x1e0/0x1e0 [ 31.807803] [] sk_destruct+0x47/0x80 [ 31.807809] [] __sk_free+0x57/0x230 [ 31.807815] [] sk_free+0x23/0x30 [ 31.807821] [] pppol2tp_release+0x23d/0x2e0 [ 31.807828] [] sock_release+0x8d/0x1e0 [ 31.807834] [] sock_close+0x16/0x20 [ 31.807842] [] __fput+0x28c/0x6e0 [ 31.807849] [] ____fput+0x15/0x20 [ 31.807855] [] task_work_run+0x115/0x190 [ 31.807862] [] exit_to_usermode_loop+0xfc/0x120 [ 31.807868] [] syscall_return_slowpath+0x1a0/0x1e0 [ 31.807875] [] entry_SYSCALL_64_fastpath+0xe0/0xe2 [ 31.808622] Dumping ftrace buffer: [ 31.808625] (ftrace buffer empty) [ 31.808627] Kernel Offset: disabled [ 32.236658] Rebooting in 86400 seconds..