[....] Starting enhanced syslogd: rsyslogd[ 14.970092] audit: type=1400 audit(1518294745.961:4): avc: denied { syslog } for pid=3650 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 '10.128.15.200' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 26.647842] ================================================================== [ 26.655217] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xe9/0x110 [ 26.662544] Read of size 4 at addr ffff8801c27b2000 by task syzkaller179921/3807 [ 26.670041] [ 26.671641] CPU: 1 PID: 3807 Comm: syzkaller179921 Not tainted 4.9.80-g8a174b47 #31 [ 26.679402] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.688725] ffff8801d74c7c60 ffffffff81d94be9 ffffea000709ec80 ffff8801c27b2000 [ 26.696691] 0000000000000000 ffff8801c27b2000 ffffffff82ed49f0 ffff8801d74c7c98 [ 26.704655] ffffffff8153e113 ffff8801c27b2000 0000000000000004 0000000000000000 [ 26.712621] Call Trace: [ 26.715178] [] dump_stack+0xc1/0x128 [ 26.720509] [] ? sock_release+0x1e0/0x1e0 [ 26.726277] [] print_address_description+0x73/0x280 [ 26.732911] [] ? sock_release+0x1e0/0x1e0 [ 26.738680] [] kasan_report+0x275/0x360 [ 26.744273] [] ? pppol2tp_session_destruct+0xe9/0x110 [ 26.751079] [] __asan_report_load4_noabort+0x14/0x20 [ 26.757798] [] pppol2tp_session_destruct+0xe9/0x110 [ 26.764435] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 26.770719] [] __sk_destruct+0x53/0x570 [ 26.776309] [] ? sock_release+0x1e0/0x1e0 [ 26.782073] [] sk_destruct+0x47/0x80 [ 26.787404] [] __sk_free+0x57/0x230 [ 26.792645] [] sk_free+0x23/0x30 [ 26.797626] [] pppol2tp_release+0x23d/0x2e0 [ 26.803566] [] sock_release+0x8d/0x1e0 [ 26.809071] [] sock_close+0x16/0x20 [ 26.814326] [] __fput+0x28c/0x6e0 [ 26.819394] [] ____fput+0x15/0x20 [ 26.824465] [] task_work_run+0x115/0x190 [ 26.830144] [] exit_to_usermode_loop+0xfc/0x120 [ 26.836432] [] syscall_return_slowpath+0x1a0/0x1e0 [ 26.842979] [] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 26.849523] [ 26.851120] Allocated by task 3806: [ 26.854715] save_stack_trace+0x16/0x20 [ 26.858656] save_stack+0x43/0xd0 [ 26.862077] kasan_kmalloc+0xad/0xe0 [ 26.865757] __kmalloc+0x11d/0x310 [ 26.869265] l2tp_session_create+0x38/0x1770 [ 26.873639] pppol2tp_connect+0x10fe/0x18f0 [ 26.877929] SYSC_connect+0x1b6/0x310 [ 26.881695] SyS_connect+0x24/0x30 [ 26.885675] entry_SYSCALL_64_fastpath+0x29/0xe8 [ 26.890400] [ 26.891996] Freed by task 3806: [ 26.895242] save_stack_trace+0x16/0x20 [ 26.899186] save_stack+0x43/0xd0 [ 26.902605] kasan_slab_free+0x72/0xc0 [ 26.906461] kfree+0x103/0x300 [ 26.909619] l2tp_session_free+0x166/0x200 [ 26.913819] l2tp_tunnel_closeall+0x26c/0x3a0 [ 26.918280] l2tp_udp_encap_destroy+0x87/0xe0 [ 26.922741] udpv6_destroy_sock+0xb1/0xd0 [ 26.926854] sk_common_release+0x6b/0x2f0 [ 26.930971] udp_lib_close+0x15/0x20 [ 26.934651] inet_release+0xfa/0x1d0 [ 26.938330] inet6_release+0x50/0x70 [ 26.942009] sock_release+0x8d/0x1e0 [ 26.945691] sock_close+0x16/0x20 [ 26.949111] __fput+0x28c/0x6e0 [ 26.952357] ____fput+0x15/0x20 [ 26.955603] task_work_run+0x115/0x190 [ 26.959456] exit_to_usermode_loop+0xfc/0x120 [ 26.963917] syscall_return_slowpath+0x1a0/0x1e0 [ 26.968641] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 26.973361] [ 26.974961] The buggy address belongs to the object at ffff8801c27b2000 [ 26.974961] which belongs to the cache kmalloc-512 of size 512 [ 26.987581] The buggy address is located 0 bytes inside of [ 26.987581] 512-byte region [ffff8801c27b2000, ffff8801c27b2200) [ 26.999243] The buggy address belongs to the page: [ 27.004141] page:ffffea000709ec80 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 27.014302] flags: 0x8000000000004080(slab|head) [ 27.019021] page dumped because: kasan: bad access detected [ 27.024693] [ 27.026286] Memory state around the buggy address: [ 27.031182] ffff8801c27b1f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.038512] ffff8801c27b1f80: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc [ 27.045840] >ffff8801c27b2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.053167] ^ [ 27.056501] ffff8801c27b2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.063825] ffff8801c27b2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.071146] ================================================================== [ 27.078471] Disabling lock debugging due to kernel taint [ 27.084648] Kernel panic - not syncing: panic_on_warn set ... [ 27.084648] [ 27.092007] CPU: 1 PID: 3807 Comm: syzkaller179921 Tainted: G B 4.9.80-g8a174b47 #31 [ 27.100982] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.110311] ffff8801d74c7bb8 ffffffff81d94be9 ffffffff841970c7 ffff8801d74c7c90 [ 27.118286] 0000000000000000 ffff8801c27b2000 ffffffff82ed49f0 ffff8801d74c7c80 [ 27.126265] ffffffff8142f5c1 0000000041b58ab3 ffffffff8418ab38 ffffffff8142f405 [ 27.134235] Call Trace: [ 27.136797] [] dump_stack+0xc1/0x128 [ 27.142131] [] ? sock_release+0x1e0/0x1e0 [ 27.147897] [] panic+0x1bc/0x3a8 [ 27.152882] [] ? percpu_up_read_preempt_enable.constprop.53+0xd7/0xd7 [ 27.161080] [] ? preempt_schedule+0x25/0x30 [ 27.167021] [] ? ___preempt_schedule+0x16/0x18 [ 27.173222] [] kasan_end_report+0x50/0x50 [ 27.178990] [] kasan_report+0x167/0x360 [ 27.184582] [] ? pppol2tp_session_destruct+0xe9/0x110 [ 27.191391] [] __asan_report_load4_noabort+0x14/0x20 [ 27.198112] [] pppol2tp_session_destruct+0xe9/0x110 [ 27.204745] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 27.211034] [] __sk_destruct+0x53/0x570 [ 27.216628] [] ? sock_release+0x1e0/0x1e0 [ 27.222395] [] sk_destruct+0x47/0x80 [ 27.227726] [] __sk_free+0x57/0x230 [ 27.232972] [] sk_free+0x23/0x30 [ 27.237957] [] pppol2tp_release+0x23d/0x2e0 [ 27.243896] [] sock_release+0x8d/0x1e0 [ 27.249401] [] sock_close+0x16/0x20 [ 27.254646] [] __fput+0x28c/0x6e0 [ 27.259716] [] ____fput+0x15/0x20 [ 27.264787] [] task_work_run+0x115/0x190 [ 27.270468] [] exit_to_usermode_loop+0xfc/0x120 [ 27.276754] [] syscall_return_slowpath+0x1a0/0x1e0 [ 27.283308] [] entry_SYSCALL_64_fastpath+0xe6/0xe8 [ 27.290262] Dumping ftrace buffer: [ 27.293773] (ftrace buffer empty) [ 27.297450] Kernel Offset: disabled [ 27.301045] Rebooting in 86400 seconds..