[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.321446] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. [ 13.616078] random: sshd: uninitialized urandom read (32 bytes read) [ 13.939013] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 15.074575] random: sshd: uninitialized urandom read (32 bytes read) [ 29.226196] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.59' (ECDSA) to the list of known hosts. [ 34.808951] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 36.750270] ================================================================== [ 36.757684] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 36.764930] Read of size 4 at addr ffff8801c54bd900 by task syz-executor028/3901 [ 36.772431] [ 36.774034] CPU: 1 PID: 3901 Comm: syz-executor028 Not tainted 4.9.112-g9e79039 #7 [ 36.781709] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 36.791050] ffff8801d9617cb0 ffffffff81eb3249 ffffea0007152f00 ffff8801c54bd900 [ 36.799037] 0000000000000000 ffff8801c54bd900 ffffffff83013be0 ffff8801d9617ce8 [ 36.807018] ffffffff81567bd9 ffff8801c54bd900 0000000000000004 0000000000000000 [ 36.814998] Call Trace: [ 36.817561] [] dump_stack+0xc1/0x128 [ 36.822899] [] ? sock_release+0x1c0/0x1c0 [ 36.828669] [] print_address_description+0x6c/0x234 [ 36.835307] [] ? sock_release+0x1c0/0x1c0 [ 36.841077] [] kasan_report.cold.6+0x242/0x2fe [ 36.847286] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 36.854013] [] __asan_report_load4_noabort+0x14/0x20 [ 36.860753] [] l2tp_session_queue_purge+0xf4/0x100 [ 36.867330] [] ? sock_release+0x1c0/0x1c0 [ 36.873106] [] pppol2tp_release+0x1fb/0x2e0 [ 36.879050] [] sock_release+0x96/0x1c0 [ 36.884563] [] sock_close+0x16/0x20 [ 36.889815] [] __fput+0x263/0x700 [ 36.894891] [] ____fput+0x15/0x20 [ 36.899966] [] task_work_run+0x10c/0x180 [ 36.905688] [] exit_to_usermode_loop+0xfc/0x120 [ 36.911993] [] do_syscall_64+0x364/0x490 [ 36.917685] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 36.924581] [ 36.926207] Allocated by task 3901: [ 36.929807] save_stack_trace+0x16/0x20 [ 36.933757] save_stack+0x43/0xd0 [ 36.937192] kasan_kmalloc+0xc7/0xe0 [ 36.940888] __kmalloc+0x11d/0x300 [ 36.944409] l2tp_session_create+0x38/0x16f0 [ 36.948796] pppol2tp_connect+0x10d7/0x18f0 [ 36.953094] SYSC_connect+0x1b8/0x300 [ 36.956871] SyS_connect+0x24/0x30 [ 36.960425] do_syscall_64+0x1a6/0x490 [ 36.964289] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 36.969362] [ 36.970964] Freed by task 3899: [ 36.974222] save_stack_trace+0x16/0x20 [ 36.978170] save_stack+0x43/0xd0 [ 36.981596] kasan_slab_free+0x72/0xc0 [ 36.985459] kfree+0xfb/0x310 [ 36.988542] l2tp_session_free+0x166/0x200 [ 36.992750] l2tp_tunnel_closeall+0x284/0x350 [ 36.997225] l2tp_udp_encap_destroy+0x87/0xe0 [ 37.001700] udpv6_destroy_sock+0xb1/0xd0 [ 37.005822] sk_common_release+0x6d/0x300 [ 37.009948] udp_lib_close+0x15/0x20 [ 37.013641] inet_release+0xff/0x1d0 [ 37.017333] inet6_release+0x50/0x70 [ 37.021023] sock_release+0x96/0x1c0 [ 37.024712] sock_close+0x16/0x20 [ 37.028145] __fput+0x263/0x700 [ 37.031405] ____fput+0x15/0x20 [ 37.034662] task_work_run+0x10c/0x180 [ 37.038529] exit_to_usermode_loop+0xfc/0x120 [ 37.043011] do_syscall_64+0x364/0x490 [ 37.046887] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 37.051967] [ 37.053576] The buggy address belongs to the object at ffff8801c54bd900 [ 37.053576] which belongs to the cache kmalloc-512 of size 512 [ 37.066218] The buggy address is located 0 bytes inside of [ 37.066218] 512-byte region [ffff8801c54bd900, ffff8801c54bdb00) [ 37.077912] The buggy address belongs to the page: [ 37.082834] page:ffffea0007152f00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 37.093035] flags: 0x8000000000004080(slab|head) [ 37.097775] page dumped because: kasan: bad access detected [ 37.103464] [ 37.105071] Memory state around the buggy address: [ 37.109987] ffff8801c54bd800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 37.117336] ffff8801c54bd880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 37.124683] >ffff8801c54bd900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 37.132052] ^ [ 37.135421] ffff8801c54bd980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 37.142768] ffff8801c54bda00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 37.150111] ================================================================== [ 37.157457] Disabling lock debugging due to kernel taint [ 37.163037] Kernel panic - not syncing: panic_on_warn set ... [ 37.163037] [ 37.170406] CPU: 1 PID: 3901 Comm: syz-executor028 Tainted: G B 4.9.112-g9e79039 #7 [ 37.179303] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 37.188642] ffff8801d9617c10 ffffffff81eb3249 ffffffff843c775f 00000000ffffffff [ 37.196658] 0000000000000000 0000000000000001 ffffffff83013be0 ffff8801d9617cd0 [ 37.204695] ffffffff81421a55 0000000041b58ab3 ffffffff843bae78 ffffffff81421896 [ 37.212676] Call Trace: [ 37.215252] [] dump_stack+0xc1/0x128 [ 37.220601] [] ? sock_release+0x1c0/0x1c0 [ 37.226395] [] panic+0x1bf/0x3bc [ 37.231386] [] ? add_taint.cold.6+0x16/0x16 [ 37.237329] [] ? ___preempt_schedule+0x16/0x18 [ 37.243542] [] kasan_end_report+0x47/0x4f [ 37.249311] [] kasan_report.cold.6+0x76/0x2fe [ 37.255446] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 37.262177] [] __asan_report_load4_noabort+0x14/0x20 [ 37.268916] [] l2tp_session_queue_purge+0xf4/0x100 [ 37.275486] [] ? sock_release+0x1c0/0x1c0 [ 37.281263] [] pppol2tp_release+0x1fb/0x2e0 [ 37.287215] [] sock_release+0x96/0x1c0 [ 37.292737] [] sock_close+0x16/0x20 [ 37.297998] [] __fput+0x263/0x700 [ 37.303094] [] ____fput+0x15/0x20 [ 37.308180] [] task_work_run+0x10c/0x180 [ 37.313867] [] exit_to_usermode_loop+0xfc/0x120 [ 37.320172] [] do_syscall_64+0x364/0x490 [ 37.325869] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 37.333159] Dumping ftrace buffer: [ 37.336679] (ftrace buffer empty) [ 37.340375] Kernel Offset: disabled [ 37.343981] Rebooting in 86400 seconds..