[....] Starting enhanced syslogd: rsyslogd[ 11.841032] audit: type=1400 audit(1518443830.586:4): avc: denied { syslog } for pid=3641 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 periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Starting mcstransd: [....] 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 '10.128.0.24' (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 syzkaller login: [ 19.722316] ================================================================== [ 19.729697] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xe9/0x110 [ 19.737033] Read of size 4 at addr ffff8801c6265400 by task syzkaller617232/3796 [ 19.744534] [ 19.746133] CPU: 0 PID: 3796 Comm: syzkaller617232 Not tainted 4.9.80-g8a174b47 #39 [ 19.753897] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 19.763223] ffff8801d98e7c18 ffffffff81d94be9 ffffea0007189900 ffff8801c6265400 [ 19.771204] 0000000000000000 ffff8801c6265400 ffffffff82ed49f0 ffff8801d98e7c50 [ 19.779176] ffffffff8153e113 ffff8801c6265400 0000000000000004 0000000000000000 [ 19.787148] Call Trace: [ 19.789709] [] dump_stack+0xc1/0x128 [ 19.795044] [] ? sock_release+0x1e0/0x1e0 [ 19.800816] [] print_address_description+0x73/0x280 [ 19.807453] [] ? sock_release+0x1e0/0x1e0 [ 19.813221] [] kasan_report+0x275/0x360 [ 19.818816] [] ? pppol2tp_session_destruct+0xe9/0x110 [ 19.825626] [] __asan_report_load4_noabort+0x14/0x20 [ 19.832347] [] pppol2tp_session_destruct+0xe9/0x110 [ 19.838985] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 19.845272] [] __sk_destruct+0x53/0x570 [ 19.850867] [] ? sock_release+0x1e0/0x1e0 [ 19.856634] [] sk_destruct+0x47/0x80 [ 19.861966] [] __sk_free+0x57/0x230 [ 19.867210] [] sk_free+0x23/0x30 [ 19.872197] [] pppol2tp_release+0x23d/0x2e0 [ 19.878136] [] sock_release+0x8d/0x1e0 [ 19.883644] [] sock_close+0x16/0x20 [ 19.888890] [] __fput+0x28c/0x6e0 [ 19.893962] [] ____fput+0x15/0x20 [ 19.899037] [] task_work_run+0x115/0x190 [ 19.904718] [] exit_to_usermode_loop+0xfc/0x120 [ 19.911004] [] do_fast_syscall_32+0x5de/0x890 [ 19.917119] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 19.923753] [] entry_SYSENTER_compat+0x74/0x83 [ 19.929951] [ 19.931547] Allocated by task 3796: [ 19.935144] save_stack_trace+0x16/0x20 [ 19.939089] save_stack+0x43/0xd0 [ 19.942511] kasan_kmalloc+0xad/0xe0 [ 19.946192] __kmalloc+0x11d/0x310 [ 19.949702] l2tp_session_create+0x38/0x1770 [ 19.954079] pppol2tp_connect+0x10fe/0x18f0 [ 19.958372] SYSC_connect+0x1b6/0x310 [ 19.962141] SyS_connect+0x24/0x30 [ 19.965650] do_fast_syscall_32+0x2f7/0x890 [ 19.969940] entry_SYSENTER_compat+0x74/0x83 [ 19.974315] [ 19.975913] Freed by task 3797: [ 19.979161] save_stack_trace+0x16/0x20 [ 19.983104] save_stack+0x43/0xd0 [ 19.987403] kasan_slab_free+0x72/0xc0 [ 19.991261] kfree+0x103/0x300 [ 19.994425] l2tp_session_free+0x166/0x200 [ 19.998632] l2tp_tunnel_closeall+0x26c/0x3a0 [ 20.003094] l2tp_udp_encap_destroy+0x87/0xe0 [ 20.007562] udpv6_destroy_sock+0xb1/0xd0 [ 20.011679] sk_common_release+0x6b/0x2f0 [ 20.015794] udp_lib_close+0x15/0x20 [ 20.019479] inet_release+0xfa/0x1d0 [ 20.023162] inet6_release+0x50/0x70 [ 20.026843] sock_release+0x8d/0x1e0 [ 20.030525] sock_close+0x16/0x20 [ 20.033947] __fput+0x28c/0x6e0 [ 20.037194] ____fput+0x15/0x20 [ 20.040444] task_work_run+0x115/0x190 [ 20.044303] exit_to_usermode_loop+0xfc/0x120 [ 20.048766] do_fast_syscall_32+0x5de/0x890 [ 20.053059] entry_SYSENTER_compat+0x74/0x83 [ 20.057433] [ 20.059030] The buggy address belongs to the object at ffff8801c6265400 [ 20.059030] which belongs to the cache kmalloc-512 of size 512 [ 20.071653] The buggy address is located 0 bytes inside of [ 20.071653] 512-byte region [ffff8801c6265400, ffff8801c6265600) [ 20.083320] The buggy address belongs to the page: [ 20.088220] page:ffffea0007189900 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 20.098386] flags: 0x8000000000004080(slab|head) [ 20.103107] page dumped because: kasan: bad access detected [ 20.108785] [ 20.110382] Memory state around the buggy address: [ 20.115366] ffff8801c6265300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb executing program [ 20.122694] ffff8801c6265380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 20.130022] >ffff8801c6265400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 20.137349] ^ [ 20.140684] ffff8801c6265480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 20.148013] ffff8801c6265500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 20.155338] ================================================================== [ 20.162664] Disabling lock debugging due to kernel taint [ 20.170424] Kernel panic - not syncing: panic_on_warn set ... [ 20.170424] [ 20.177777] CPU: 0 PID: 3796 Comm: syzkaller617232 Tainted: G B 4.9.80-g8a174b47 #39 [ 20.186753] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 20.196080] ffff8801d98e7b70 ffffffff81d94be9 ffffffff841970c7 ffff8801d98e7c48 [ 20.204053] 0000000000000000 ffff8801c6265400 ffffffff82ed49f0 ffff8801d98e7c38 [ 20.212024] ffffffff8142f5c1 0000000041b58ab3 ffffffff8418ab38 ffffffff8142f405 [ 20.219992] Call Trace: [ 20.222554] [] dump_stack+0xc1/0x128 [ 20.227889] [] ? sock_release+0x1e0/0x1e0 [ 20.233657] [] panic+0x1bc/0x3a8 [ 20.239338] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 20.247536] [] ? preempt_schedule+0x25/0x30 [ 20.253477] [] ? ___preempt_schedule+0x16/0x18 [ 20.259678] [] kasan_end_report+0x50/0x50 [ 20.265446] [] kasan_report+0x167/0x360 [ 20.271042] [] ? pppol2tp_session_destruct+0xe9/0x110 [ 20.277850] [] __asan_report_load4_noabort+0x14/0x20 [ 20.284570] [] pppol2tp_session_destruct+0xe9/0x110 [ 20.291205] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 20.297492] [] __sk_destruct+0x53/0x570 [ 20.303085] [] ? sock_release+0x1e0/0x1e0 [ 20.308852] [] sk_destruct+0x47/0x80 [ 20.314186] [] __sk_free+0x57/0x230 [ 20.319432] [] sk_free+0x23/0x30 [ 20.324416] [] pppol2tp_release+0x23d/0x2e0 [ 20.330359] [] sock_release+0x8d/0x1e0 [ 20.335867] [] sock_close+0x16/0x20 [ 20.341116] [] __fput+0x28c/0x6e0 [ 20.346189] [] ____fput+0x15/0x20 [ 20.351261] [] task_work_run+0x115/0x190 [ 20.356941] [] exit_to_usermode_loop+0xfc/0x120 [ 20.363228] [] do_fast_syscall_32+0x5de/0x890 [ 20.369345] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 20.375979] [] entry_SYSENTER_compat+0x74/0x83 [ 20.382630] Dumping ftrace buffer: [ 20.386141] (ftrace buffer empty) [ 20.389819] Kernel Offset: disabled [ 20.393412] Rebooting in 86400 seconds..