[....] Starting enhanced syslogd: rsyslogd[ 13.530595] audit: type=1400 audit(1519824401.457:4): avc: denied { syslog } for pid=3635 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 '10.128.0.20' (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 syzkaller login: [ 25.092640] l2tp_core: tunl 3: fd 62 wrong protocol, got 1, expected 17 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 [ 25.599032] l2tp_core: tunl 3: fd 126 wrong protocol, got 1, expected 17 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 executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 26.545459] l2tp_core: tunl 3: fd 254 wrong protocol, got 1, expected 17 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 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 [ 27.530877] ================================================================== [ 27.538251] BUG: KASAN: use-after-free in pppol2tp_release+0x293/0x2e0 [ 27.544884] Read of size 4 at addr ffff8801b8e93180 by task syzkaller269944/3792 [ 27.552383] [ 27.553980] CPU: 0 PID: 3792 Comm: syzkaller269944 Not tainted 4.9.84-ge7f51a5 #45 [ 27.561650] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.570976] ffff8801d7a7fce0 ffffffff81d956b9 ffffea0006e3a480 ffff8801b8e93180 [ 27.578962] 0000000000000000 ffff8801b8e93180 ffffffff82ed59f0 ffff8801d7a7fd18 [ 27.586935] ffffffff8153e1a3 ffff8801b8e93180 0000000000000004 0000000000000000 [ 27.594916] Call Trace: [ 27.597480] [] dump_stack+0xc1/0x128 [ 27.602815] [] ? sock_release+0x1e0/0x1e0 [ 27.608583] [] print_address_description+0x73/0x280 [ 27.615216] [] ? sock_release+0x1e0/0x1e0 [ 27.620982] [] kasan_report+0x275/0x360 [ 27.626575] [] ? pppol2tp_release+0x293/0x2e0 [ 27.632688] [] __asan_report_load4_noabort+0x14/0x20 [ 27.639410] [] pppol2tp_release+0x293/0x2e0 [ 27.645350] [] sock_release+0x8d/0x1e0 [ 27.650855] [] sock_close+0x16/0x20 [ 27.656099] [] __fput+0x28c/0x6e0 [ 27.661174] [] ____fput+0x15/0x20 [ 27.666247] [] task_work_run+0x115/0x190 [ 27.671926] [] exit_to_usermode_loop+0xfc/0x120 [ 27.678214] [] do_syscall_64+0x36f/0x490 [ 27.683896] [] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 27.690787] [ 27.692388] Allocated by task 3792: [ 27.695984] save_stack_trace+0x16/0x20 [ 27.699929] save_stack+0x43/0xd0 [ 27.703348] kasan_kmalloc+0xad/0xe0 [ 27.707031] __kmalloc+0x11d/0x310 [ 27.710972] l2tp_session_create+0x38/0x1770 [ 27.715352] pppol2tp_connect+0x10fe/0x18f0 [ 27.719646] SYSC_connect+0x1b6/0x310 [ 27.723414] SyS_connect+0x24/0x30 [ 27.726922] do_syscall_64+0x1a4/0x490 [ 27.730779] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 27.735847] [ 27.737442] Freed by task 3793: [ 27.740693] save_stack_trace+0x16/0x20 [ 27.744637] save_stack+0x43/0xd0 [ 27.748059] kasan_slab_free+0x72/0xc0 [ 27.751912] kfree+0x103/0x300 [ 27.755075] l2tp_session_free+0x166/0x200 [ 27.759278] l2tp_tunnel_closeall+0x26c/0x3a0 [ 27.763741] l2tp_udp_encap_destroy+0x87/0xe0 [ 27.768205] udpv6_destroy_sock+0xb1/0xd0 [ 27.772320] sk_common_release+0x6b/0x2f0 [ 27.776437] udp_lib_close+0x15/0x20 [ 27.780120] inet_release+0xfa/0x1d0 [ 27.783801] inet6_release+0x50/0x70 [ 27.787487] sock_release+0x8d/0x1e0 [ 27.791169] sock_close+0x16/0x20 [ 27.794591] __fput+0x28c/0x6e0 [ 27.797839] ____fput+0x15/0x20 [ 27.801086] task_work_run+0x115/0x190 [ 27.804941] exit_to_usermode_loop+0xfc/0x120 [ 27.809402] do_syscall_64+0x36f/0x490 [ 27.813256] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 27.818322] [ 27.819919] The buggy address belongs to the object at ffff8801b8e93180 [ 27.819919] which belongs to the cache kmalloc-512 of size 512 [ 27.832545] The buggy address is located 0 bytes inside of [ 27.832545] 512-byte region [ffff8801b8e93180, ffff8801b8e93380) [ 27.844212] The buggy address belongs to the page: [ 27.849109] page:ffffea0006e3a480 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 27.859277] flags: 0x8000000000004080(slab|head) [ 27.863997] page dumped because: kasan: bad access detected [ 27.869674] [ 27.871268] Memory state around the buggy address: [ 27.876175] ffff8801b8e93080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.883501] ffff8801b8e93100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 27.890830] >ffff8801b8e93180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.898158] ^ [ 27.901491] ffff8801b8e93200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.908820] ffff8801b8e93280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.916147] ================================================================== [ 27.923473] Disabling lock debugging due to kernel taint [ 27.929530] Kernel panic - not syncing: panic_on_warn set ... [ 27.929530] [ 27.936883] CPU: 0 PID: 3792 Comm: syzkaller269944 Tainted: G B 4.9.84-ge7f51a5 #45 [ 27.945774] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.955099] ffff8801d7a7fc38 ffffffff81d956b9 ffffffff8419784f ffff8801d7a7fd10 [ 27.963067] 0000000000000000 ffff8801b8e93180 ffffffff82ed59f0 ffff8801d7a7fd00 [ 27.971035] ffffffff8142f571 0000000041b58ab3 ffffffff8418b2c0 ffffffff8142f3b5 [ 27.979010] Call Trace: [ 27.981571] [] dump_stack+0xc1/0x128 [ 27.986904] [] ? sock_release+0x1e0/0x1e0 [ 27.992669] [] panic+0x1bc/0x3a8 [ 27.997655] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 28.005855] [] ? preempt_schedule+0x25/0x30 [ 28.011798] [] ? ___preempt_schedule+0x16/0x18 [ 28.017999] [] kasan_end_report+0x50/0x50 [ 28.023764] [] kasan_report+0x167/0x360 [ 28.029358] [] ? pppol2tp_release+0x293/0x2e0 [ 28.035474] [] __asan_report_load4_noabort+0x14/0x20 [ 28.042197] [] pppol2tp_release+0x293/0x2e0 [ 28.048141] [] sock_release+0x8d/0x1e0 [ 28.053648] [] sock_close+0x16/0x20 [ 28.058891] [] __fput+0x28c/0x6e0 [ 28.063962] [] ____fput+0x15/0x20 [ 28.069035] [] task_work_run+0x115/0x190 [ 28.074713] [] exit_to_usermode_loop+0xfc/0x120 [ 28.081000] [] do_syscall_64+0x36f/0x490 [ 28.086680] [] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 28.093972] Dumping ftrace buffer: [ 28.097482] (ftrace buffer empty) [ 28.101161] Kernel Offset: disabled [ 28.104757] Rebooting in 86400 seconds..