[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.285001] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 16.103696] random: sshd: uninitialized urandom read (32 bytes read) [ 16.406486] random: sshd: uninitialized urandom read (32 bytes read) [ 17.359664] random: sshd: uninitialized urandom read (32 bytes read) [ 17.489520] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.16' (ECDSA) to the list of known hosts. [ 22.900977] random: sshd: uninitialized urandom read (32 bytes read) net.ipv6.conf.syz_tun.accept_dad = 0 net.ipv6.conf.syz_tun.router_solicitations = 0 [ 22.981061] IPVS: Creating netns size=2536 id=1 executing program [ 23.106139] ================================================================== [ 23.113548] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 23.120796] Read of size 4 at addr ffff8801ca38f680 by task syz-executor077/3812 [ 23.128300] [ 23.129923] CPU: 1 PID: 3812 Comm: syz-executor077 Not tainted 4.9.113-g90e7a90 #16 [ 23.137688] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 23.147019] ffff8801d9ae7cb0 ffffffff81eb4569 ffffea000728e380 ffff8801ca38f680 [ 23.155026] 0000000000000000 ffff8801ca38f680 ffffffff83014be0 ffff8801d9ae7ce8 [ 23.163033] ffffffff81567c59 ffff8801ca38f680 0000000000000004 0000000000000000 [ 23.171029] Call Trace: [ 23.173595] [] dump_stack+0xc1/0x128 [ 23.178937] [] ? sock_release+0x1c0/0x1c0 [ 23.184709] [] print_address_description+0x6c/0x234 [ 23.191359] [] ? sock_release+0x1c0/0x1c0 [ 23.197144] [] kasan_report.cold.6+0x242/0x2fe [ 23.203363] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 23.210105] [] __asan_report_load4_noabort+0x14/0x20 [ 23.216843] [] l2tp_session_queue_purge+0xf4/0x100 [ 23.223401] [] ? sock_release+0x1c0/0x1c0 [ 23.229174] [] pppol2tp_release+0x1fb/0x2e0 [ 23.235123] [] sock_release+0x96/0x1c0 [ 23.240635] [] sock_close+0x16/0x20 [ 23.245899] [] __fput+0x263/0x700 [ 23.250977] [] ____fput+0x15/0x20 [ 23.256056] [] task_work_run+0x10c/0x180 [ 23.261743] [] exit_to_usermode_loop+0xfc/0x120 [ 23.268035] [] do_syscall_64+0x364/0x490 [ 23.273722] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.280621] [ 23.282226] Allocated by task 3811: [ 23.285829] save_stack_trace+0x16/0x20 [ 23.289777] save_stack+0x43/0xd0 [ 23.293206] kasan_kmalloc+0xc7/0xe0 [ 23.296902] __kmalloc+0x11d/0x300 [ 23.300419] l2tp_session_create+0x38/0x16f0 [ 23.304800] pppol2tp_connect+0x10d7/0x18f0 [ 23.309099] SYSC_connect+0x1b8/0x300 [ 23.312894] SyS_connect+0x24/0x30 [ 23.316410] do_syscall_64+0x1a6/0x490 [ 23.320272] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.325344] [ 23.326947] Freed by task 3811: [ 23.330203] save_stack_trace+0x16/0x20 [ 23.334155] save_stack+0x43/0xd0 [ 23.337582] kasan_slab_free+0x72/0xc0 [ 23.341456] kfree+0xfb/0x310 [ 23.344539] l2tp_session_free+0x166/0x200 [ 23.348746] l2tp_tunnel_closeall+0x284/0x350 [ 23.353226] l2tp_udp_encap_destroy+0x87/0xe0 [ 23.357696] udpv6_destroy_sock+0xb1/0xd0 [ 23.361816] sk_common_release+0x6d/0x300 [ 23.365938] udp_lib_close+0x15/0x20 [ 23.369641] inet_release+0xff/0x1d0 [ 23.373330] inet6_release+0x50/0x70 [ 23.377030] sock_release+0x96/0x1c0 [ 23.380718] sock_close+0x16/0x20 [ 23.384147] __fput+0x263/0x700 [ 23.387409] ____fput+0x15/0x20 [ 23.390664] task_work_run+0x10c/0x180 [ 23.394527] exit_to_usermode_loop+0xfc/0x120 [ 23.398995] do_syscall_64+0x364/0x490 [ 23.402856] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.407934] [ 23.409542] The buggy address belongs to the object at ffff8801ca38f680 [ 23.409542] which belongs to the cache kmalloc-512 of size 512 [ 23.422258] The buggy address is located 0 bytes inside of [ 23.422258] 512-byte region [ffff8801ca38f680, ffff8801ca38f880) [ 23.433932] The buggy address belongs to the page: [ 23.438838] page:ffffea000728e380 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 23.446803] flags: 0x8000000000004080(slab|head) [ 23.446805] page dumped because: kasan: bad access detected [ 23.446806] [ 23.446808] Memory state around the buggy address: [ 23.446815] ffff8801ca38f580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 23.446819] ffff8801ca38f600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 23.446824] >ffff8801ca38f680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 23.446826] ^ [ 23.446830] ffff8801ca38f700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 23.446835] ffff8801ca38f780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 23.446837] ================================================================== [ 23.446839] Disabling lock debugging due to kernel taint [ 23.450623] Kernel panic - not syncing: panic_on_warn set ... [ 23.450623] [ 23.450632] CPU: 1 PID: 3812 Comm: syz-executor077 Tainted: G B 4.9.113-g90e7a90 #16 [ 23.450636] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 23.450650] ffff8801d9ae7c10 ffffffff81eb4569 ffffffff843c87af 00000000ffffffff [ 23.450658] 0000000000000000 0000000000000001 ffffffff83014be0 ffff8801d9ae7cd0 [ 23.450667] ffffffff81421a55 0000000041b58ab3 ffffffff843bbec8 ffffffff81421896 [ 23.450669] Call Trace: [ 23.450686] [] dump_stack+0xc1/0x128 [ 23.450699] [] ? sock_release+0x1c0/0x1c0 [ 23.450709] [] panic+0x1bf/0x3bc [ 23.450717] [] ? add_taint.cold.6+0x16/0x16 [ 23.450727] [] ? ___preempt_schedule+0x16/0x18 [ 23.450736] [] kasan_end_report+0x47/0x4f [ 23.450743] [] kasan_report.cold.6+0x76/0x2fe [ 23.450753] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 23.450763] [] __asan_report_load4_noabort+0x14/0x20 [ 23.450770] [] l2tp_session_queue_purge+0xf4/0x100 [ 23.450778] [] ? sock_release+0x1c0/0x1c0 [ 23.450786] [] pppol2tp_release+0x1fb/0x2e0 [ 23.450793] [] sock_release+0x96/0x1c0 [ 23.450800] [] sock_close+0x16/0x20 [ 23.450808] [] __fput+0x263/0x700 [ 23.450816] [] ____fput+0x15/0x20 [ 23.450828] [] task_work_run+0x10c/0x180 [ 23.450835] [] exit_to_usermode_loop+0xfc/0x120 [ 23.450842] [] do_syscall_64+0x364/0x490 [ 23.450852] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.451277] Dumping ftrace buffer: [ 23.451281] (ftrace buffer empty) [ 23.451284] Kernel Offset: disabled [ 23.699905] Rebooting in 86400 seconds..