[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.878715] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 19.920764] random: sshd: uninitialized urandom read (32 bytes read) [ 20.522956] random: sshd: uninitialized urandom read (32 bytes read) [ 21.366135] random: sshd: uninitialized urandom read (32 bytes read) [ 21.510393] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.56' (ECDSA) to the list of known hosts. [ 26.995081] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 27.146907] ================================================================== [ 27.154352] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 27.161638] Read of size 4 at addr ffff8801cb254280 by task syz-executor082/3816 [ 27.169154] [ 27.170769] CPU: 1 PID: 3816 Comm: syz-executor082 Not tainted 4.9.99-gc462abb #20 [ 27.178454] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.187818] ffff8801b60e7cb0 ffffffff81eb0f09 ffffea00072c9500 ffff8801cb254280 [ 27.195886] 0000000000000000 ffff8801cb254280 ffffffff8300fbe0 ffff8801b60e7ce8 [ 27.203959] ffffffff815652eb ffff8801cb254280 0000000000000004 0000000000000000 [ 27.213086] Call Trace: [ 27.215654] [] dump_stack+0xc1/0x128 [ 27.220993] [] ? sock_release+0x1c0/0x1c0 [ 27.226770] [] print_address_description+0x6c/0x234 [ 27.233421] [] ? sock_release+0x1c0/0x1c0 [ 27.239199] [] kasan_report.cold.6+0x242/0x2fe [ 27.245413] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 27.252141] [] __asan_report_load4_noabort+0x14/0x20 [ 27.258873] [] l2tp_session_queue_purge+0xf4/0x100 [ 27.265426] [] ? sock_release+0x1c0/0x1c0 [ 27.271199] [] pppol2tp_release+0x1fb/0x2e0 [ 27.277151] [] sock_release+0x96/0x1c0 [ 27.282676] [] sock_close+0x16/0x20 [ 27.287929] [] __fput+0x263/0x700 [ 27.293022] [] ____fput+0x15/0x20 [ 27.298138] [] task_work_run+0x10c/0x180 [ 27.303830] [] exit_to_usermode_loop+0xfc/0x120 [ 27.310127] [] do_syscall_64+0x364/0x490 [ 27.315831] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.322737] [ 27.324366] Allocated by task 3815: [ 27.327978] save_stack_trace+0x16/0x20 [ 27.331933] save_stack+0x43/0xd0 [ 27.335361] kasan_kmalloc+0xc7/0xe0 [ 27.339063] __kmalloc+0x11d/0x300 [ 27.342594] l2tp_session_create+0x38/0x16f0 [ 27.348024] pppol2tp_connect+0x10d7/0x18f0 [ 27.352322] SYSC_connect+0x1b8/0x300 [ 27.356108] SyS_connect+0x24/0x30 [ 27.359634] do_syscall_64+0x1a6/0x490 [ 27.363496] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.368567] [ 27.370167] Freed by task 3815: [ 27.373428] save_stack_trace+0x16/0x20 [ 27.377378] save_stack+0x43/0xd0 [ 27.380802] kasan_slab_free+0x72/0xc0 [ 27.384663] kfree+0xfb/0x310 [ 27.387751] l2tp_session_free+0x166/0x200 [ 27.391960] l2tp_tunnel_closeall+0x284/0x350 [ 27.396428] l2tp_udp_encap_destroy+0x87/0xe0 [ 27.400896] udpv6_destroy_sock+0xb1/0xd0 [ 27.405029] sk_common_release+0x6d/0x300 [ 27.409153] udp_lib_close+0x15/0x20 [ 27.412849] inet_release+0xff/0x1d0 [ 27.416553] inet6_release+0x50/0x70 [ 27.420245] sock_release+0x96/0x1c0 [ 27.423942] sock_close+0x16/0x20 [ 27.427378] __fput+0x263/0x700 [ 27.430650] ____fput+0x15/0x20 [ 27.433903] task_work_run+0x10c/0x180 [ 27.437788] exit_to_usermode_loop+0xfc/0x120 [ 27.442257] do_syscall_64+0x364/0x490 [ 27.446129] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.451200] [ 27.452810] The buggy address belongs to the object at ffff8801cb254280 [ 27.452810] which belongs to the cache kmalloc-512 of size 512 [ 27.465459] The buggy address is located 0 bytes inside of [ 27.465459] 512-byte region [ffff8801cb254280, ffff8801cb254480) [ 27.477153] The buggy address belongs to the page: [ 27.482083] page:ffffea00072c9500 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 27.492286] flags: 0x8000000000004080(slab|head) [ 27.497013] page dumped because: kasan: bad access detected [ 27.502691] [ 27.504290] Memory state around the buggy address: [ 27.509195] ffff8801cb254180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.516525] ffff8801cb254200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 27.523859] >ffff8801cb254280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.531186] ^ [ 27.534521] ffff8801cb254300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.541851] ffff8801cb254380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.549183] ================================================================== [ 27.556519] Disabling lock debugging due to kernel taint [ 27.562094] Kernel panic - not syncing: panic_on_warn set ... [ 27.562094] [ 27.569450] CPU: 1 PID: 3816 Comm: syz-executor082 Tainted: G B 4.9.99-gc462abb #20 [ 27.578347] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.587688] ffff8801b60e7c10 ffffffff81eb0f09 ffffffff843c4fe5 00000000ffffffff [ 27.595680] 0000000000000000 0000000000000001 ffffffff8300fbe0 ffff8801b60e7cd0 [ 27.603676] ffffffff8141f855 0000000041b58ab3 ffffffff843b86e8 ffffffff8141f696 [ 27.611654] Call Trace: [ 27.614219] [] dump_stack+0xc1/0x128 [ 27.619569] [] ? sock_release+0x1c0/0x1c0 [ 27.625344] [] panic+0x1bf/0x3bc [ 27.630340] [] ? add_taint.cold.6+0x16/0x16 [ 27.636385] [] ? ___preempt_schedule+0x16/0x18 [ 27.642597] [] kasan_end_report+0x47/0x4f [ 27.648375] [] kasan_report.cold.6+0x76/0x2fe [ 27.654502] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 27.661245] [] __asan_report_load4_noabort+0x14/0x20 [ 27.667981] [] l2tp_session_queue_purge+0xf4/0x100 [ 27.674543] [] ? sock_release+0x1c0/0x1c0 [ 27.680317] [] pppol2tp_release+0x1fb/0x2e0 [ 27.686283] [] sock_release+0x96/0x1c0 [ 27.691822] [] sock_close+0x16/0x20 [ 27.697076] [] __fput+0x263/0x700 [ 27.702152] [] ____fput+0x15/0x20 [ 27.707230] [] task_work_run+0x10c/0x180 [ 27.712922] [] exit_to_usermode_loop+0xfc/0x120 [ 27.719218] [] do_syscall_64+0x364/0x490 [ 27.724913] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.732386] Dumping ftrace buffer: [ 27.735915] (ftrace buffer empty) [ 27.739600] Kernel Offset: disabled [ 27.743201] Rebooting in 86400 seconds..