[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.124340] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.484247] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) [ 21.728803] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) [ 22.800245] random: sshd: uninitialized urandom read (32 bytes read, 126 bits of entropy available) [ 22.900114] random: nonblocking pool is initialized Warning: Permanently added '10.128.0.44' (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 [ 35.726678] ================================================================== [ 35.734084] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 35.741352] Read of size 4 at addr ffff8800b40d6780 by task syz-executor453/4286 [ 35.748871] [ 35.750490] CPU: 0 PID: 4286 Comm: syz-executor453 Not tainted 4.4.133-g3f51ea2 #51 [ 35.758268] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 35.767616] 0000000000000000 5abf41b45dba134f ffff8801d88c7b50 ffffffff81e0e4cd [ 35.775654] ffffea0002d03580 ffff8800b40d6780 0000000000000000 ffff8800b40d6780 [ 35.783684] ffffffff82f191d0 ffff8801d88c7b88 ffffffff815154cc ffff8800b40d6780 [ 35.791705] Call Trace: [ 35.794278] [] dump_stack+0xc1/0x124 [ 35.799631] [] ? sock_release+0x1c0/0x1c0 [ 35.805416] [] print_address_description+0x6c/0x216 [ 35.812068] [] ? sock_release+0x1c0/0x1c0 [ 35.817854] [] kasan_report.cold.7+0x175/0x2f7 [ 35.824077] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 35.830822] [] __asan_report_load4_noabort+0x14/0x20 [ 35.837568] [] l2tp_session_queue_purge+0xf4/0x100 [ 35.844156] [] ? sock_release+0x1c0/0x1c0 [ 35.849950] [] pppol2tp_release+0x1ff/0x310 [ 35.855914] [] sock_release+0x96/0x1c0 [ 35.861445] [] sock_close+0x16/0x20 [ 35.866713] [] __fput+0x235/0x6f0 [ 35.871807] [] ____fput+0x15/0x20 [ 35.876902] [] task_work_run+0x10f/0x190 [ 35.882600] [] do_exit+0x9e5/0x26b0 [ 35.887873] [] ? release_task.part.17+0x1200/0x1200 [ 35.894527] [] ? __do_page_fault+0x385/0xa10 [ 35.900588] [] ? retint_user+0x18/0x3c [ 35.906117] [] do_group_exit+0x111/0x330 [ 35.911818] [] ? trace_hardirqs_on_thunk+0x17/0x19 [ 35.918392] [] SyS_exit_group+0x1d/0x20 [ 35.924005] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 35.930568] [ 35.932181] Allocated by task 4284: [ 35.935788] [] save_stack_trace+0x26/0x50 [ 35.941703] [] save_stack+0x43/0xd0 [ 35.947088] [] kasan_kmalloc+0xc7/0xe0 [ 35.952736] [] __kmalloc+0x124/0x310 [ 35.958213] [] l2tp_session_create+0x39/0x1030 [ 35.964554] [] pppol2tp_connect+0x10f0/0x1910 [ 35.970817] [] SYSC_connect+0x1b8/0x300 [ 35.976554] [] SyS_connect+0x24/0x30 [ 35.982031] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 35.988723] [ 35.990335] Freed by task 4256: [ 35.993591] [] save_stack_trace+0x26/0x50 [ 35.999507] [] save_stack+0x43/0xd0 [ 36.004987] [] kasan_slab_free+0x72/0xc0 [ 36.010813] [] kfree+0xf4/0x310 [ 36.015857] [] l2tp_session_free+0x170/0x200 [ 36.022028] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 36.028462] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 36.034894] [] udpv6_destroy_sock+0xb1/0xd0 [ 36.040984] [] sk_common_release+0x6d/0x300 [ 36.047063] [] udp_lib_close+0x15/0x20 [ 36.052706] [] inet_release+0xff/0x1d0 [ 36.058370] [] inet6_release+0x50/0x70 [ 36.064000] [] sock_release+0x96/0x1c0 [ 36.069627] [] sock_close+0x16/0x20 [ 36.074998] [] __fput+0x235/0x6f0 [ 36.080218] [] ____fput+0x15/0x20 [ 36.085436] [] task_work_run+0x10f/0x190 [ 36.091250] [] do_exit+0x9e5/0x26b0 [ 36.096615] [] do_group_exit+0x111/0x330 [ 36.102419] [] SyS_exit_group+0x1d/0x20 [ 36.108132] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 36.114808] [ 36.116418] The buggy address belongs to the object at ffff8800b40d6780 [ 36.116418] which belongs to the cache kmalloc-512 of size 512 [ 36.129061] The buggy address is located 0 bytes inside of [ 36.129061] 512-byte region [ffff8800b40d6780, ffff8800b40d6980) [ 36.140739] The buggy address belongs to the page: [ 36.145693] ------------[ cut here ]------------ [ 36.150574] WARNING: CPU: 1 PID: 4319 at kernel/locking/lockdep.c:3123 __lock_acquire+0x23b8/0x5270() [ 36.159932] DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH) [ 36.165216] Kernel panic - not syncing: panic_on_warn set ... [ 36.165216] [ 36.172896] CPU: 1 PID: 4319 Comm: ÌHÿÿÿÿutor453 Not tainted 4.4.133-g3f51ea2 #51 [ 36.180691] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 36.190034] 0000000000000000 4be4fcfc0914b425 ffff8801db307460 ffffffff81e0e4cd [ 36.198037] ffffffff83a43ec0 ffff8801d88b3000 ffffffff83a55d20 0000000000000009 [ 36.206077] 0000000000000c33 ffff8801db307520 ffffffff81409f34 0000000041b58ab3 [ 36.214193] Call Trace: [ 36.216753] [] dump_stack+0xc1/0x124 [ 36.222859] [] panic+0x19e/0x38d [ 36.227861] [] ? add_taint.cold.4+0x16/0x16 [ 36.233821] [] ? warn_slowpath_common.cold.6+0x5/0x20 [ 36.240765] [] warn_slowpath_common.cold.6+0x20/0x20 [ 36.247531] [] ? __lock_acquire+0x23b8/0x5270 [ 36.253875] [] warn_slowpath_fmt+0xbf/0x100 [ 36.259861] [] ? warn_slowpath_common+0x120/0x120 [ 36.266500] [] ? raw_local_deliver+0x66c/0xa60 [ 36.273084] [] __lock_acquire+0x23b8/0x5270 [ 36.279123] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.286156] [] ? ip_local_deliver_finish+0x64e/0xa60 [ 36.292919] [] ? ip_local_deliver_finish+0x12a/0xa60 [ 36.299701] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.306731] [] ? ip_call_ra_chain+0x540/0x540 [ 36.312884] [] ? mark_held_locks+0xc7/0x130 [ 36.318864] [] ? update_group_capacity+0x5c9/0xbf0 [ 36.325453] [] lock_acquire+0x15e/0x450 [ 36.331068] [] ? vprintk_emit+0xa9/0x840 [ 36.336765] [] _raw_spin_lock+0x36/0x50 [ 36.342402] [] ? vprintk_emit+0xa9/0x840 [ 36.348119] [] vprintk_emit+0xa9/0x840 [ 36.353664] [] ? update_sd_lb_stats+0x38a/0x33b0 [ 36.360077] [] vprintk+0x28/0x30 [ 36.365083] [] vprintk_default+0x1d/0x30 [ 36.370880] [] printk+0xaf/0xd7 [ 36.376841] [] ? log_wakeup_reason.cold.1+0x13f/0x13f [ 36.383791] [] ? check_preemption_disabled+0x3b/0x170 [ 36.390650] [] ? kasan_die_handler.cold.3+0x5/0x22 [ 36.397255] [] kasan_die_handler.cold.3+0x11/0x22 [ 36.403779] [] notifier_call_chain+0xb9/0x1e0 [ 36.409926] [] atomic_notifier_call_chain+0x7f/0x140 [ 36.416661] [] ? blocking_notifier_call_chain+0xa0/0xa0 [ 36.423856] [] notify_die+0xdf/0x160 [ 36.429394] [] ? atomic_notifier_call_chain+0x140/0x140 [ 36.436429] [] ? cpuacct_account_field+0xec/0x2f0 [ 36.442946] [] ? search_exception_tables+0x31/0x40 [ 36.449546] [] do_general_protection+0x20a/0x2b0 [ 36.455972] [] general_protection+0x28/0x30 [ 36.462002] [] ? cpuacct_account_field+0xec/0x2f0 [ 36.468500] [] ? cpuacct_charge+0x380/0x380 [ 36.474477] [] account_system_time+0x1a6/0x4c0 [ 36.480719] [] account_process_tick+0xdc/0x310 [ 36.486973] [] ? kvm_clock_read+0x23/0x40 [ 36.492795] [] update_process_times+0x23/0x70 [ 36.498971] [] tick_sched_handle.isra.15+0x55/0xf0 [ 36.505743] [] tick_sched_timer+0x72/0x120 [ 36.511652] [] ? tick_sched_do_timer+0xa0/0xa0 [ 36.517874] [] __hrtimer_run_queues+0x3ad/0x1000 [ 36.524300] [] ? retrigger_next_event+0x1c0/0x1c0 [ 36.530812] [] ? kvm_clock_read+0x23/0x40 [ 36.536602] [] ? kvm_clock_get_cycles+0x9/0x10 [ 36.542832] [] ? hrtimer_interrupt+0x12d/0x430 [ 36.549072] [] hrtimer_interrupt+0x1b1/0x430 [ 36.555137] [] local_apic_timer_interrupt+0x74/0xa0 [ 36.561807] [] smp_apic_timer_interrupt+0x7c/0xa0 [ 36.568305] [] apic_timer_interrupt+0xa0/0xb0 [ 36.574450] [ 37.700201] PANIC: double fault, error_code: 0x0