INIT: Entering runlevel: 2 [info] Using makefile-style concurrent boot in runlevel 2. [....] 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[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.24' (ECDSA) to the list of known hosts. 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 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 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 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 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 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 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 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 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 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 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 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 executing program executing program executing program executing program executing program syzkaller login: [ 43.400361] ================================================================== [ 43.407761] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xed/0x110 [ 43.415095] Read of size 4 at addr ffff8801d90e4500 by task syzkaller904363/4683 [ 43.422595] [ 43.424196] CPU: 1 PID: 4683 Comm: syzkaller904363 Not tainted 4.9.94-g8683408 #3 [ 43.431786] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 43.441115] ffff8801b5defc30 ffffffff81d9b509 ffffea0007643900 ffff8801d90e4500 [ 43.449155] 0000000000000000 ffff8801d90e4500 ffffffff82eecbe0 ffff8801b5defc68 [ 43.457146] ffffffff815652cb ffff8801d90e4500 0000000000000004 0000000000000000 [ 43.465131] Call Trace: [ 43.467710] [] dump_stack+0xc1/0x128 [ 43.473045] [] ? sock_release+0x1c0/0x1c0 [ 43.478814] [] print_address_description+0x6c/0x234 [ 43.485448] [] ? sock_release+0x1c0/0x1c0 [ 43.491221] [] kasan_report.cold.6+0x242/0x2fe [ 43.497428] [] ? pppol2tp_session_destruct+0xed/0x110 [ 43.504239] [] __asan_report_load4_noabort+0x14/0x20 [ 43.510960] [] pppol2tp_session_destruct+0xed/0x110 [ 43.517595] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 43.523883] [] __sk_destruct+0x55/0x590 [ 43.529477] [] ? sock_release+0x1c0/0x1c0 [ 43.535245] [] sk_destruct+0x63/0x80 [ 43.540579] [] __sk_free+0x15e/0x220 [ 43.545911] [] sk_free+0x2b/0x40 [ 43.550898] [] pppol2tp_release+0x239/0x2e0 [ 43.556839] [] sock_release+0x96/0x1c0 [ 43.562344] [] sock_close+0x16/0x20 [ 43.567593] [] __fput+0x263/0x700 [ 43.572682] [] ____fput+0x15/0x20 [ 43.577755] [] task_work_run+0x10c/0x180 [ 43.583434] [] exit_to_usermode_loop+0xfc/0x120 [ 43.589723] [] do_syscall_64+0x364/0x490 [ 43.595409] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 43.602301] [ 43.603907] Allocated by task 4683: [ 43.607513] save_stack_trace+0x16/0x20 [ 43.611456] save_stack+0x43/0xd0 [ 43.614879] kasan_kmalloc+0xc7/0xe0 [ 43.618563] __kmalloc+0x11d/0x300 [ 43.622074] l2tp_session_create+0x38/0x16f0 [ 43.626452] pppol2tp_connect+0x10c5/0x18e0 [ 43.630744] SYSC_connect+0x1b8/0x300 [ 43.634527] SyS_connect+0x24/0x30 [ 43.638036] do_syscall_64+0x1a6/0x490 [ 43.641894] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 43.646970] [ 43.648569] Freed by task 4684: [ 43.651818] save_stack_trace+0x16/0x20 [ 43.655761] save_stack+0x43/0xd0 [ 43.659187] kasan_slab_free+0x72/0xc0 [ 43.663044] kfree+0xfb/0x310 [ 43.666122] l2tp_session_free+0x166/0x200 [ 43.670327] l2tp_tunnel_closeall+0x284/0x350 [ 43.674792] l2tp_udp_encap_destroy+0x87/0xe0 [ 43.679280] udpv6_destroy_sock+0xb1/0xd0 [ 43.683401] sk_common_release+0x6d/0x300 [ 43.687519] udp_lib_close+0x15/0x20 [ 43.691204] inet_release+0xff/0x1d0 [ 43.694888] inet6_release+0x50/0x70 [ 43.698579] sock_release+0x96/0x1c0 [ 43.702262] sock_close+0x16/0x20 [ 43.705688] __fput+0x263/0x700 [ 43.708936] ____fput+0x15/0x20 [ 43.712190] task_work_run+0x10c/0x180 [ 43.716048] exit_to_usermode_loop+0xfc/0x120 [ 43.720513] do_syscall_64+0x364/0x490 [ 43.724373] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 43.729444] [ 43.731043] The buggy address belongs to the object at ffff8801d90e4500 [ 43.731043] which belongs to the cache kmalloc-512 of size 512 [ 43.743671] The buggy address is located 0 bytes inside of [ 43.743671] 512-byte region [ffff8801d90e4500, ffff8801d90e4700) [ 43.755346] The buggy address belongs to the page: [ 43.760259] page:ffffea0007643900 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 43.770457] flags: 0x8000000000004080(slab|head) [ 43.775183] page dumped because: kasan: bad access detected [ 43.780861] [ 43.782458] Memory state around the buggy address: [ 43.787368] ffff8801d90e4400: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc [ 43.794708] ffff8801d90e4480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 43.802045] >ffff8801d90e4500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 43.809374] ^ [ 43.812709] ffff8801d90e4580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 43.820037] ffff8801d90e4600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 43.827363] ================================================================== [ 43.834690] Disabling lock debugging due to kernel taint [ 43.840584] Kernel panic - not syncing: panic_on_warn set ... [ 43.840584] [ 43.847929] CPU: 1 PID: 4683 Comm: syzkaller904363 Tainted: G B 4.9.94-g8683408 #3 [ 43.856733] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 43.866060] ffff8801b5defb90 ffffffff81d9b509 ffffffff841a8a65 00000000ffffffff [ 43.874056] 0000000000000000 0000000000000001 ffffffff82eecbe0 ffff8801b5defc50 [ 43.882033] ffffffff8141f845 0000000041b58ab3 ffffffff8419c168 ffffffff8141f686 [ 43.890031] Call Trace: [ 43.892595] [] dump_stack+0xc1/0x128 [ 43.897943] [] ? sock_release+0x1c0/0x1c0 [ 43.903712] [] panic+0x1bf/0x3bc [ 43.908701] [] ? add_taint.cold.6+0x16/0x16 [ 43.914645] [] ? ___preempt_schedule+0x16/0x18 [ 43.920853] [] kasan_end_report+0x47/0x4f [ 43.926625] [] kasan_report.cold.6+0x76/0x2fe [ 43.932743] [] ? pppol2tp_session_destruct+0xed/0x110 [ 43.939554] [] __asan_report_load4_noabort+0x14/0x20 [ 43.946278] [] pppol2tp_session_destruct+0xed/0x110 [ 43.952924] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 43.959226] [] __sk_destruct+0x55/0x590 [ 43.965378] [] ? sock_release+0x1c0/0x1c0 [ 43.971152] [] sk_destruct+0x63/0x80 [ 43.976489] [] __sk_free+0x15e/0x220 [ 43.981831] [] sk_free+0x2b/0x40 [ 43.986822] [] pppol2tp_release+0x239/0x2e0 [ 43.992768] [] sock_release+0x96/0x1c0 [ 43.998276] [] sock_close+0x16/0x20 [ 44.003525] [] __fput+0x263/0x700 [ 44.008606] [] ____fput+0x15/0x20 [ 44.013682] [] task_work_run+0x10c/0x180 [ 44.019364] [] exit_to_usermode_loop+0xfc/0x120 [ 44.025663] [] do_syscall_64+0x364/0x490 [ 44.031354] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 44.038642] Dumping ftrace buffer: [ 44.042159] (ftrace buffer empty) [ 44.045842] Kernel Offset: disabled [ 44.049444] Rebooting in 86400 seconds..