[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.440927] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 27.167895] random: sshd: uninitialized urandom read (32 bytes read) [ 27.515353] random: sshd: uninitialized urandom read (32 bytes read) [ 27.883539] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.27' (ECDSA) to the list of known hosts. [ 33.630336] urandom_read: 1 callbacks suppressed [ 33.630340] random: sshd: uninitialized urandom read (32 bytes read) 2018/08/20 10:51:38 parsed 1 programs [ 34.942655] random: cc1: uninitialized urandom read (8 bytes read) 2018/08/20 10:51:40 executed programs: 0 [ 35.890804] IPVS: Creating netns size=2536 id=1 [ 36.008876] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready [ 36.020684] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready [ 36.062562] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready [ 36.073997] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready [ 36.115537] IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready [ 36.127073] IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready [ 36.138915] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready [ 36.152704] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready [ 36.196904] ip (3911) used greatest stack depth: 23624 bytes left [ 36.640251] IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready [ 36.665141] IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready [ 36.671673] IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready [ 36.679133] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready [ 40.008157] ================================================================== [ 40.015534] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 40.022786] Read of size 4 at addr ffff8801d4562500 by task syz-executor0/4418 [ 40.030116] [ 40.031722] CPU: 1 PID: 4418 Comm: syz-executor0 Not tainted 4.9.122-g54068d6 #30 [ 40.039315] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 40.048690] ffff8801d0127ca0 ffffffff81eb8829 ffffea0007515880 ffff8801d4562500 [ 40.056765] 0000000000000000 ffff8801d4562500 ffffffff83019be0 ffff8801d0127cd8 [ 40.064756] ffffffff8156b6be ffff8801d4562500 0000000000000004 0000000000000000 [ 40.072756] Call Trace: [ 40.075331] [] dump_stack+0xc1/0x128 [ 40.080673] [] ? sock_release+0x1c0/0x1c0 [ 40.086447] [] print_address_description+0x6c/0x234 [ 40.093087] [] ? sock_release+0x1c0/0x1c0 [ 40.098858] [] kasan_report.cold.6+0x242/0x2fe [ 40.105064] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 40.111792] [] __asan_report_load4_noabort+0x14/0x20 [ 40.118523] [] l2tp_session_queue_purge+0xf4/0x100 [ 40.125128] [] ? sock_release+0x1c0/0x1c0 [ 40.130915] [] pppol2tp_release+0x1fb/0x2e0 [ 40.136864] [] sock_release+0x96/0x1c0 [ 40.142374] [] sock_close+0x16/0x20 [ 40.147630] [] __fput+0x263/0x700 [ 40.152708] [] ____fput+0x15/0x20 [ 40.157791] [] task_work_run+0x10c/0x180 [ 40.163480] [] exit_to_usermode_loop+0xfc/0x120 [ 40.169784] [] do_fast_syscall_32+0x5c3/0x870 [ 40.175906] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 40.182546] [] entry_SYSENTER_compat+0x90/0xa2 [ 40.188746] [ 40.190353] Allocated by task 4418: [ 40.193951] save_stack_trace+0x16/0x20 [ 40.197895] save_stack+0x43/0xd0 [ 40.201321] kasan_kmalloc+0xc7/0xe0 [ 40.205006] __kmalloc+0x11d/0x300 [ 40.208522] l2tp_session_create+0x38/0x16f0 [ 40.212903] pppol2tp_connect+0x10d7/0x18f0 [ 40.217196] SYSC_connect+0x1b8/0x300 [ 40.220966] SyS_connect+0x24/0x30 [ 40.224480] do_fast_syscall_32+0x2f7/0x870 [ 40.228783] entry_SYSENTER_compat+0x90/0xa2 [ 40.233160] [ 40.234758] Freed by task 4416: [ 40.238023] save_stack_trace+0x16/0x20 [ 40.241967] save_stack+0x43/0xd0 [ 40.245390] kasan_slab_free+0x72/0xc0 [ 40.249248] kfree+0xfb/0x310 [ 40.252329] l2tp_session_free+0x166/0x200 [ 40.256533] l2tp_tunnel_closeall+0x284/0x350 [ 40.261000] l2tp_udp_encap_destroy+0x87/0xe0 [ 40.265466] udpv6_destroy_sock+0xb1/0xd0 [ 40.269585] sk_common_release+0x6d/0x300 [ 40.273707] udp_lib_close+0x15/0x20 [ 40.277393] inet_release+0xff/0x1d0 [ 40.281080] inet6_release+0x50/0x70 [ 40.284775] sock_release+0x96/0x1c0 [ 40.288462] sock_close+0x16/0x20 [ 40.291890] __fput+0x263/0x700 [ 40.295143] ____fput+0x15/0x20 [ 40.298398] task_work_run+0x10c/0x180 [ 40.302258] exit_to_usermode_loop+0xfc/0x120 [ 40.306727] do_fast_syscall_32+0x5c3/0x870 [ 40.311025] entry_SYSENTER_compat+0x90/0xa2 [ 40.315401] [ 40.317001] The buggy address belongs to the object at ffff8801d4562500 [ 40.317001] which belongs to the cache kmalloc-512 of size 512 [ 40.329670] The buggy address is located 0 bytes inside of [ 40.329670] 512-byte region [ffff8801d4562500, ffff8801d4562700) [ 40.341348] The buggy address belongs to the page: [ 40.346253] page:ffffea0007515880 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 40.356441] flags: 0x8000000000004080(slab|head) [ 40.361175] page dumped because: kasan: bad access detected [ 40.366860] [ 40.368460] Memory state around the buggy address: [ 40.373361] ffff8801d4562400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 40.380692] ffff8801d4562480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 40.388033] >ffff8801d4562500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 40.395364] ^ [ 40.398702] ffff8801d4562580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 40.406092] ffff8801d4562600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 40.413432] ================================================================== [ 40.420769] Disabling lock debugging due to kernel taint [ 40.426671] Kernel panic - not syncing: panic_on_warn set ... [ 40.426671] [ 40.434018] CPU: 1 PID: 4418 Comm: syz-executor0 Tainted: G B 4.9.122-g54068d6 #30 [ 40.442826] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 40.452160] ffff8801d0127c00 ffffffff81eb8829 ffffffff843c81db 00000000ffffffff [ 40.460142] 0000000000000000 0000000000000001 ffffffff83019be0 ffff8801d0127cc0 [ 40.468181] ffffffff81423f35 0000000041b58ab3 ffffffff843bb838 ffffffff81423d76 [ 40.476162] Call Trace: [ 40.478725] [] dump_stack+0xc1/0x128 [ 40.484066] [] ? sock_release+0x1c0/0x1c0 [ 40.489845] [] panic+0x1bf/0x3bc [ 40.494836] [] ? add_taint.cold.6+0x16/0x16 [ 40.500789] [] ? ___preempt_schedule+0x16/0x18 [ 40.507043] [] kasan_end_report+0x47/0x4f [ 40.512825] [] kasan_report.cold.6+0x76/0x2fe [ 40.518951] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 40.525682] [] __asan_report_load4_noabort+0x14/0x20 [ 40.532422] [] l2tp_session_queue_purge+0xf4/0x100 [ 40.538984] [] ? sock_release+0x1c0/0x1c0 [ 40.544766] [] pppol2tp_release+0x1fb/0x2e0 [ 40.550726] [] sock_release+0x96/0x1c0 [ 40.556245] [] sock_close+0x16/0x20 [ 40.561499] [] __fput+0x263/0x700 [ 40.566575] [] ____fput+0x15/0x20 [ 40.571651] [] task_work_run+0x10c/0x180 [ 40.577335] [] exit_to_usermode_loop+0xfc/0x120 [ 40.583633] [] do_fast_syscall_32+0x5c3/0x870 [ 40.589756] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 40.596415] [] entry_SYSENTER_compat+0x90/0xa2 [ 40.602979] Dumping ftrace buffer: [ 40.606500] (ftrace buffer empty) [ 40.610228] Kernel Offset: disabled [ 40.613840] Rebooting in 86400 seconds..