[....] Starting enhanced syslogd: rsyslogd[ 12.390705] audit: type=1400 audit(1518665929.263:4): avc: denied { syslog } for pid=3649 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 '10.128.0.27' (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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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: [ 25.265069] ================================================================== [ 25.272451] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xe8/0x100 [ 25.279689] Read of size 4 at addr ffff8801d4771b80 by task syzkaller653530/5400 [ 25.287186] [ 25.288782] CPU: 0 PID: 5400 Comm: syzkaller653530 Not tainted 4.9.81-gd2c57b6 #34 [ 25.296456] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.305776] ffff8801d3907878 ffffffff81d94de9 ffffea000751dc00 ffff8801d4771b80 [ 25.313731] 0000000000000000 ffff8801d4771b80 ffffffff82ed49f0 ffff8801d39078b0 [ 25.321689] ffffffff8153e173 ffff8801d4771b80 0000000000000004 0000000000000000 [ 25.329652] Call Trace: [ 25.332207] [] dump_stack+0xc1/0x128 [ 25.337537] [] ? sock_release+0x1e0/0x1e0 [ 25.343301] [] print_address_description+0x73/0x280 [ 25.349933] [] ? sock_release+0x1e0/0x1e0 [ 25.355695] [] kasan_report+0x275/0x360 [ 25.361378] [] ? l2tp_session_queue_purge+0xe8/0x100 [ 25.368105] [] __asan_report_load4_noabort+0x14/0x20 [ 25.374828] [] l2tp_session_queue_purge+0xe8/0x100 [ 25.381376] [] ? sock_release+0x1e0/0x1e0 [ 25.387144] [] pppol2tp_release+0x1ff/0x2e0 [ 25.393081] [] sock_release+0x8d/0x1e0 [ 25.398582] [] sock_close+0x16/0x20 [ 25.403822] [] __fput+0x28c/0x6e0 [ 25.408888] [] ____fput+0x15/0x20 [ 25.413960] [] task_work_run+0x115/0x190 [ 25.419634] [] do_exit+0x7e7/0x2a40 [ 25.424877] [] ? release_task+0x1240/0x1240 [ 25.430814] [] ? __dequeue_signal+0xa3/0x550 [ 25.436840] [] ? recalc_sigpending+0x72/0x90 [ 25.442866] [] do_group_exit+0x108/0x320 [ 25.448543] [] get_signal+0x4d4/0x14e0 [ 25.454044] [] ? exit_robust_list+0x230/0x230 [ 25.460155] [] do_signal+0x87/0x19f0 [ 25.465486] [] ? __fdget+0x18/0x20 [ 25.470642] [] ? sockfd_lookup_light+0x118/0x160 [ 25.477012] [] ? fput+0xd2/0x140 [ 25.481992] [] ? setup_sigcontext+0x7d0/0x7d0 [ 25.488104] [] ? __sys_sendmsg+0xee/0x190 [ 25.493868] [] ? SyS_shutdown+0x1b0/0x1b0 [ 25.499631] [] ? do_futex+0x15c0/0x15c0 [ 25.505220] [] ? __do_page_fault+0x3bd/0xd40 [ 25.511247] [] ? exit_to_usermode_loop+0xac/0x120 [ 25.517701] [] exit_to_usermode_loop+0xe1/0x120 [ 25.523989] [] do_syscall_64+0x370/0x490 [ 25.529673] [] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 25.536563] [ 25.538158] Allocated by task 5393: [ 25.541750] save_stack_trace+0x16/0x20 [ 25.545690] save_stack+0x43/0xd0 [ 25.549107] kasan_kmalloc+0xad/0xe0 [ 25.552784] __kmalloc+0x11d/0x310 [ 25.556292] l2tp_session_create+0x38/0x1770 [ 25.560667] pppol2tp_connect+0x10fe/0x18f0 [ 25.564956] SYSC_connect+0x1b6/0x310 [ 25.568719] SyS_connect+0x24/0x30 [ 25.572222] do_syscall_64+0x1a5/0x490 [ 25.576075] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 25.581139] [ 25.582732] Freed by task 5390: [ 25.585975] save_stack_trace+0x16/0x20 [ 25.589915] save_stack+0x43/0xd0 [ 25.593333] kasan_slab_free+0x72/0xc0 [ 25.597186] kfree+0x103/0x300 [ 25.600346] l2tp_session_free+0x166/0x200 [ 25.604546] l2tp_tunnel_closeall+0x26c/0x3a0 [ 25.609004] l2tp_udp_encap_destroy+0x87/0xe0 [ 25.613463] udpv6_destroy_sock+0xb1/0xd0 [ 25.617577] sk_common_release+0x6b/0x2f0 [ 25.621691] udp_lib_close+0x15/0x20 [ 25.625371] inet_release+0xfa/0x1d0 [ 25.629050] inet6_release+0x50/0x70 [ 25.632728] sock_release+0x8d/0x1e0 [ 25.636411] sock_close+0x16/0x20 [ 25.639828] __fput+0x28c/0x6e0 [ 25.643071] ____fput+0x15/0x20 [ 25.646314] task_work_run+0x115/0x190 [ 25.650170] do_exit+0x7e7/0x2a40 [ 25.653591] do_group_exit+0x108/0x320 [ 25.657447] get_signal+0x4d4/0x14e0 [ 25.661130] do_signal+0x87/0x19f0 [ 25.664638] exit_to_usermode_loop+0xe1/0x120 [ 25.669097] do_syscall_64+0x370/0x490 [ 25.672951] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 25.678017] [ 25.679613] The buggy address belongs to the object at ffff8801d4771b80 [ 25.679613] which belongs to the cache kmalloc-512 of size 512 [ 25.692232] The buggy address is located 0 bytes inside of [ 25.692232] 512-byte region [ffff8801d4771b80, ffff8801d4771d80) [ 25.703894] The buggy address belongs to the page: [ 25.708789] page:ffffea000751dc00 count:1 mapcount:0 mapping: (null) index:0xffff8801d4771400 compound_mapcount: 0 [ 25.720254] flags: 0x8000000000004080(slab|head) [ 25.724972] page dumped because: kasan: bad access detected [ 25.730644] [ 25.732239] Memory state around the buggy address: [ 25.737131] ffff8801d4771a80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc [ 25.744457] ffff8801d4771b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 25.751783] >ffff8801d4771b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.759110] ^ executing program executing program executing program executing program executing program [ 25.762448] ffff8801d4771c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.769774] ffff8801d4771c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.777103] ================================================================== [ 25.784437] Disabling lock debugging due to kernel taint [ 25.792199] Kernel panic - not syncing: panic_on_warn set ... [ 25.792199] [ 25.799573] CPU: 0 PID: 5400 Comm: syzkaller653530 Tainted: G B 4.9.81-gd2c57b6 #34 executing program executing program [ 25.808483] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.817818] ffff8801d39077d0 ffffffff81d94de9 ffffffff84197637 ffff8801d39078a8 [ 25.825802] 0000000000000000 ffff8801d4771b80 ffffffff82ed49f0 ffff8801d3907898 [ 25.833804] ffffffff8142f621 0000000041b58ab3 ffffffff8418b0a8 ffffffff8142f465 [ 25.841811] Call Trace: [ 25.844374] [] dump_stack+0xc1/0x128 [ 25.849708] [] ? sock_release+0x1e0/0x1e0 [ 25.855477] [] panic+0x1bc/0x3a8 [ 25.860462] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 25.868659] [] ? preempt_schedule+0x25/0x30 [ 25.874600] [] ? ___preempt_schedule+0x16/0x18 [ 25.880800] [] kasan_end_report+0x50/0x50 [ 25.886565] [] kasan_report+0x167/0x360 [ 25.892157] [] ? l2tp_session_queue_purge+0xe8/0x100 [ 25.898880] [] __asan_report_load4_noabort+0x14/0x20 [ 25.905601] [] l2tp_session_queue_purge+0xe8/0x100 [ 25.912146] [] ? sock_release+0x1e0/0x1e0 [ 25.917911] [] pppol2tp_release+0x1ff/0x2e0 [ 25.923852] [] sock_release+0x8d/0x1e0 [ 25.929355] [] sock_close+0x16/0x20 [ 25.934599] [] __fput+0x28c/0x6e0 [ 25.939673] [] ____fput+0x15/0x20 [ 25.944742] [] task_work_run+0x115/0x190 [ 25.950429] [] do_exit+0x7e7/0x2a40 [ 25.955676] [] ? release_task+0x1240/0x1240 [ 25.961613] [] ? __dequeue_signal+0xa3/0x550 [ 25.967639] [] ? recalc_sigpending+0x72/0x90 [ 25.973665] [] do_group_exit+0x108/0x320 [ 25.979342] [] get_signal+0x4d4/0x14e0 [ 25.984852] [] ? exit_robust_list+0x230/0x230 [ 25.990968] [] do_signal+0x87/0x19f0 [ 25.996299] [] ? __fdget+0x18/0x20 [ 26.001460] [] ? sockfd_lookup_light+0x118/0x160 [ 26.007835] [] ? fput+0xd2/0x140 [ 26.012828] [] ? setup_sigcontext+0x7d0/0x7d0 [ 26.018944] [] ? __sys_sendmsg+0xee/0x190 [ 26.024715] [] ? SyS_shutdown+0x1b0/0x1b0 [ 26.030479] [] ? do_futex+0x15c0/0x15c0 [ 26.036075] [] ? __do_page_fault+0x3bd/0xd40 [ 26.042102] [] ? exit_to_usermode_loop+0xac/0x120 [ 26.048561] [] exit_to_usermode_loop+0xe1/0x120 [ 26.054854] [] do_syscall_64+0x370/0x490 [ 26.060541] [] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 26.067850] Dumping ftrace buffer: [ 26.071358] (ftrace buffer empty) [ 26.075034] Kernel Offset: disabled [ 26.078626] Rebooting in 86400 seconds..