[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 12.656834] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. [ 13.287393] random: sshd: uninitialized urandom read (32 bytes read) [ 13.627305] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 14.914264] random: sshd: uninitialized urandom read (32 bytes read) [ 15.032504] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.31' (ECDSA) to the list of known hosts. [ 20.521012] random: sshd: uninitialized urandom read (32 bytes read) 2018/06/25 17:49:57 parsed 1 programs [ 21.957643] random: cc1: uninitialized urandom read (8 bytes read) 2018/06/25 17:49:59 executed programs: 0 [ 22.741742] IPVS: Creating netns size=2536 id=1 [ 22.877953] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready [ 22.888966] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready [ 22.929949] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready [ 22.941991] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready [ 22.981841] IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready [ 22.992825] IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready [ 23.004268] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready [ 23.016973] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready [ 23.466423] IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready [ 23.489135] IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready [ 23.495276] IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready [ 23.502646] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready [ 24.799974] ================================================================== [ 24.807352] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 24.814599] Read of size 4 at addr ffff8801d47f3400 by task syz-executor0/4221 [ 24.821926] [ 24.823531] CPU: 0 PID: 4221 Comm: syz-executor0 Not tainted 4.9.109-g7cecc75 #5 [ 24.831035] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 24.840374] ffff8801d924fca0 ffffffff81eb3e29 ffffea000751fc80 ffff8801d47f3400 [ 24.848354] 0000000000000000 ffff8801d47f3400 ffffffff83013be0 ffff8801d924fcd8 [ 24.856331] ffffffff81567a89 ffff8801d47f3400 0000000000000004 0000000000000000 [ 24.864321] Call Trace: [ 24.866881] [] dump_stack+0xc1/0x128 [ 24.872223] [] ? sock_release+0x1c0/0x1c0 [ 24.877998] [] print_address_description+0x6c/0x234 [ 24.884637] [] ? sock_release+0x1c0/0x1c0 [ 24.890406] [] kasan_report.cold.6+0x242/0x2fe [ 24.896611] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 24.903332] [] __asan_report_load4_noabort+0x14/0x20 [ 24.910055] [] l2tp_session_queue_purge+0xf4/0x100 [ 24.916607] [] ? sock_release+0x1c0/0x1c0 [ 24.922377] [] pppol2tp_release+0x1fb/0x2e0 [ 24.928319] [] sock_release+0x96/0x1c0 [ 24.933828] [] sock_close+0x16/0x20 [ 24.939075] [] __fput+0x263/0x700 [ 24.944149] [] ____fput+0x15/0x20 [ 24.949232] [] task_work_run+0x10c/0x180 [ 24.954916] [] exit_to_usermode_loop+0xfc/0x120 [ 24.961204] [] do_fast_syscall_32+0x5c3/0x870 [ 24.967317] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 24.973955] [] entry_SYSENTER_compat+0x90/0xa2 [ 24.980153] [ 24.981752] Allocated by task 4221: [ 24.985360] save_stack_trace+0x16/0x20 [ 24.989305] save_stack+0x43/0xd0 [ 24.992729] kasan_kmalloc+0xc7/0xe0 [ 24.996412] __kmalloc+0x11d/0x300 [ 24.999921] l2tp_session_create+0x38/0x16f0 [ 25.004297] pppol2tp_connect+0x10d7/0x18f0 [ 25.008592] SYSC_connect+0x1b8/0x300 [ 25.012361] SyS_connect+0x24/0x30 [ 25.015874] do_fast_syscall_32+0x2f7/0x870 [ 25.020177] entry_SYSENTER_compat+0x90/0xa2 [ 25.024555] [ 25.026152] Freed by task 4220: [ 25.029400] save_stack_trace+0x16/0x20 [ 25.033344] save_stack+0x43/0xd0 [ 25.036767] kasan_slab_free+0x72/0xc0 [ 25.040625] kfree+0xfb/0x310 [ 25.043715] l2tp_session_free+0x166/0x200 [ 25.047918] l2tp_tunnel_closeall+0x284/0x350 [ 25.052385] l2tp_udp_encap_destroy+0x87/0xe0 [ 25.056851] udp_destroy_sock+0x118/0x1a0 [ 25.060970] sk_common_release+0x6d/0x300 [ 25.065087] udp_lib_close+0x15/0x20 [ 25.068781] inet_release+0xff/0x1d0 [ 25.072463] sock_release+0x96/0x1c0 [ 25.076144] sock_close+0x16/0x20 [ 25.079566] __fput+0x263/0x700 [ 25.082817] ____fput+0x15/0x20 [ 25.086068] task_work_run+0x10c/0x180 [ 25.089924] exit_to_usermode_loop+0xfc/0x120 [ 25.094389] do_fast_syscall_32+0x5c3/0x870 [ 25.098680] entry_SYSENTER_compat+0x90/0xa2 [ 25.103054] [ 25.104654] The buggy address belongs to the object at ffff8801d47f3400 [ 25.104654] which belongs to the cache kmalloc-512 of size 512 [ 25.117279] The buggy address is located 0 bytes inside of [ 25.117279] 512-byte region [ffff8801d47f3400, ffff8801d47f3600) [ 25.128948] The buggy address belongs to the page: [ 25.133852] page:ffffea000751fc80 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 25.144033] flags: 0x8000000000004080(slab|head) [ 25.148755] page dumped because: kasan: bad access detected [ 25.154430] [ 25.156029] Memory state around the buggy address: [ 25.160926] ffff8801d47f3300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.168265] ffff8801d47f3380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 25.175595] >ffff8801d47f3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.182935] ^ [ 25.186271] ffff8801d47f3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.193613] ffff8801d47f3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 25.200939] ================================================================== [ 25.208270] Disabling lock debugging due to kernel taint [ 25.214060] Kernel panic - not syncing: panic_on_warn set ... [ 25.214060] [ 25.221411] CPU: 0 PID: 4221 Comm: syz-executor0 Tainted: G B 4.9.109-g7cecc75 #5 [ 25.230130] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.239460] ffff8801d924fc00 ffffffff81eb3e29 ffffffff843c62e7 00000000ffffffff [ 25.247447] 0000000000000000 0000000000000000 ffffffff83013be0 ffff8801d924fcc0 [ 25.255431] ffffffff81421925 0000000041b58ab3 ffffffff843b9a00 ffffffff81421766 [ 25.263418] Call Trace: [ 25.265980] [] dump_stack+0xc1/0x128 [ 25.271320] [] ? sock_release+0x1c0/0x1c0 [ 25.277093] [] panic+0x1bf/0x3bc [ 25.282084] [] ? add_taint.cold.6+0x16/0x16 [ 25.288026] [] ? ___preempt_schedule+0x16/0x18 [ 25.294236] [] kasan_end_report+0x47/0x4f [ 25.300011] [] kasan_report.cold.6+0x76/0x2fe [ 25.306127] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 25.312851] [] __asan_report_load4_noabort+0x14/0x20 [ 25.319574] [] l2tp_session_queue_purge+0xf4/0x100 [ 25.326124] [] ? sock_release+0x1c0/0x1c0 [ 25.331898] [] pppol2tp_release+0x1fb/0x2e0 [ 25.337840] [] sock_release+0x96/0x1c0 [ 25.343348] [] sock_close+0x16/0x20 [ 25.348598] [] __fput+0x263/0x700 [ 25.353672] [] ____fput+0x15/0x20 [ 25.358748] [] task_work_run+0x10c/0x180 [ 25.364430] [] exit_to_usermode_loop+0xfc/0x120 [ 25.370720] [] do_fast_syscall_32+0x5c3/0x870 [ 25.376838] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 25.383483] [] entry_SYSENTER_compat+0x90/0xa2 [ 25.390158] Dumping ftrace buffer: [ 25.393669] (ftrace buffer empty) [ 25.397351] Kernel Offset: disabled [ 25.400949] Rebooting in 86400 seconds..