[....] 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[ 21.520814] random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 26.527258] random: sshd: uninitialized urandom read (32 bytes read, 40 bits of entropy available) [ 26.824302] random: sshd: uninitialized urandom read (32 bytes read, 40 bits of entropy available) [ 27.932822] random: nonblocking pool is initialized Warning: Permanently added '10.128.0.33' (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 executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 65.739877] ================================================================== [ 65.747724] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 65.755110] Read of size 4 at addr ffff8801d4aa1180 by task syz-executor378/6399 [ 65.762636] [ 65.764268] CPU: 0 PID: 6399 Comm: syz-executor378 Not tainted 4.4.138-g226f96b #63 [ 65.772038] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 65.781686] 0000000000000000 bfd40c655dc4ba38 ffff8801d45178b0 ffffffff81e0ed0d [ 65.789716] ffffea000752a800 ffff8801d4aa1180 0000000000000000 ffff8801d4aa1180 [ 65.797736] ffffffff82f1a2b0 ffff8801d45178e8 ffffffff81515a16 ffff8801d4aa1180 [ 65.805763] Call Trace: [ 65.808335] [] dump_stack+0xc1/0x124 [ 65.813681] [] ? sock_release+0x1c0/0x1c0 [ 65.819465] [] print_address_description+0x6c/0x216 [ 65.826129] [] ? sock_release+0x1c0/0x1c0 [ 65.831922] [] kasan_report.cold.7+0x175/0x2f7 [ 65.838230] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 65.845069] [] __asan_report_load4_noabort+0x14/0x20 [ 65.851820] [] l2tp_session_queue_purge+0xf4/0x100 [ 65.858394] [] ? sock_release+0x1c0/0x1c0 [ 65.864191] [] pppol2tp_release+0x1ff/0x310 [ 65.870148] [] sock_release+0x96/0x1c0 [ 65.875665] [] sock_close+0x16/0x20 [ 65.880944] [] __fput+0x235/0x6f0 [ 65.886026] [] ____fput+0x15/0x20 [ 65.891194] [] task_work_run+0x10f/0x190 [ 65.896894] [] do_exit+0x9e5/0x26b0 [ 65.902172] [] ? debug_check_no_locks_freed+0x210/0x210 [ 65.909167] [] ? release_task.part.17+0x1200/0x1200 [ 65.915942] [] ? debug_check_no_locks_freed+0x210/0x210 [ 65.922941] [] ? recalc_sigpending+0x76/0xa0 [ 65.929687] [] do_group_exit+0x111/0x330 [ 65.935751] [] get_signal+0x4ec/0x14b0 [ 65.941282] [] do_signal+0x8b/0x1d30 [ 65.946808] [] ? setup_sigcontext+0x780/0x780 [ 65.952942] [] ? get_unused_fd_flags+0xd0/0xd0 [ 65.959158] [] ? kernel_sock_shutdown+0x80/0x80 [ 65.965461] [] ? SyS_futex+0x1f8/0x300 [ 65.970987] [] ? fd_install+0x4d/0x60 [ 65.976596] [] ? exit_to_usermode_loop+0xe4/0x160 [ 65.983070] [] exit_to_usermode_loop+0x11a/0x160 [ 65.989738] [] syscall_return_slowpath+0x1b5/0x1f0 [ 65.996308] [] int_ret_from_sys_call+0x25/0xa3 [ 66.002526] [ 66.004141] Allocated by task 6396: [ 66.007806] [] save_stack_trace+0x26/0x50 [ 66.013726] [] save_stack+0x43/0xd0 [ 66.019121] [] kasan_kmalloc+0xc7/0xe0 [ 66.024816] [] __kmalloc+0x124/0x310 [ 66.030336] [] l2tp_session_create+0x39/0x1030 [ 66.036814] [] pppol2tp_connect+0x10f0/0x1910 [ 66.043117] [] SYSC_connect+0x1b8/0x300 [ 66.048973] [] SyS_connect+0x24/0x30 [ 66.054520] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 66.061375] [ 66.063000] Freed by task 6378: [ 66.066277] [] save_stack_trace+0x26/0x50 [ 66.072247] [] save_stack+0x43/0xd0 [ 66.077778] [] kasan_slab_free+0x72/0xc0 [ 66.083639] [] kfree+0xf4/0x310 [ 66.088743] [] l2tp_session_free+0x170/0x200 [ 66.095087] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 66.101553] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 66.108018] [] udpv6_destroy_sock+0xb1/0xd0 [ 66.115470] [] sk_common_release+0x6d/0x300 [ 66.122153] [] udp_lib_close+0x15/0x20 [ 66.128309] [] inet_release+0xff/0x1d0 [ 66.134497] [] inet6_release+0x50/0x70 [ 66.140251] [] sock_release+0x96/0x1c0 [ 66.145916] [] sock_close+0x16/0x20 [ 66.151405] [] __fput+0x235/0x6f0 [ 66.156613] [] ____fput+0x15/0x20 [ 66.161830] [] task_work_run+0x10f/0x190 [ 66.167815] [] do_exit+0x9e5/0x26b0 [ 66.173205] [] do_group_exit+0x111/0x330 [ 66.179041] [] get_signal+0x4ec/0x14b0 [ 66.184704] [] do_signal+0x8b/0x1d30 [ 66.190196] [] exit_to_usermode_loop+0x11a/0x160 [ 66.196726] [] prepare_exit_to_usermode+0xe3/0x100 [ 66.203434] [] retint_user+0x8/0x3c [ 66.208824] [ 66.210433] The buggy address belongs to the object at ffff8801d4aa1180 [ 66.210433] which belongs to the cache kmalloc-512 of size 512 [ 66.223405] The buggy address is located 0 bytes inside of [ 66.223405] 512-byte region [ffff8801d4aa1180, ffff8801d4aa1380) [ 66.235094] The buggy address belongs to the page: [ 66.252155] ------------[ cut here ]------------ [ 66.256965] WARNING: CPU: 1 PID: 3832 at kernel/locking/lockdep.c:3190 __lock_acquire+0x265f/0x5270() [ 66.266309] DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS) [ 66.271477] Kernel panic - not syncing: panic_on_warn set ... [ 66.271477] [ 66.279112] CPU: 1 PID: 3832 Comm: syz-executor378 Not tainted 4.4.138-g226f96b #63 [ 66.287056] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 66.296394] 0000000000000000 17af75a3465e2e88 ffff8801d938f5d0 ffffffff81e0ed0d [ 66.304510] ffffffff83a43da0 ffff8800baf64800 ffffffff83a55c00 0000000000000009 [ 66.312637] 0000000000000c76 ffff8801d938f690 ffffffff8140a184 0000000041b58ab3 [ 66.320895] Call Trace: [ 66.323467] [] dump_stack+0xc1/0x124 [ 66.328839] [] panic+0x19e/0x38d [ 66.334113] [] ? add_taint.cold.4+0x16/0x16 [ 66.340153] [] ? warn_slowpath_common.cold.6+0x5/0x20 [ 66.346973] [] warn_slowpath_common.cold.6+0x20/0x20 [ 66.353725] [] ? __lock_acquire+0x265f/0x5270 [ 66.359851] [] warn_slowpath_fmt+0xbf/0x100 [ 66.365803] [] ? warn_slowpath_common+0x120/0x120 [ 66.372286] [] ? depot_save_stack+0x1c9/0x610 [ 66.378419] [] __lock_acquire+0x265f/0x5270 [ 66.384367] [] ? __lock_acquire+0xa86/0x5270 [ 66.390416] [] ? kmem_cache_free+0xbe/0x340 [ 66.396366] [] ? put_files_struct+0x208/0x270 [ 66.402600] [] ? exit_files+0x83/0xb0 [ 66.408036] [] ? do_exit+0x9b7/0x26b0 [ 66.413470] [] ? do_group_exit+0x111/0x330 [ 66.419334] [] ? get_signal+0x4ec/0x14b0 [ 66.425035] [] ? debug_check_no_locks_freed+0x210/0x210 [ 66.432127] [] ? debug_check_no_locks_freed+0x210/0x210 [ 66.439138] [] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [ 66.446067] [] ? debug_check_no_locks_freed+0x210/0x210 [ 66.453083] [] lock_acquire+0x15e/0x450 [ 66.458692] [] ? dput.part.26+0x3b0/0x760 [ 66.464479] [] ? check_preemption_disabled+0x3b/0x170 [ 66.471305] [] ? dput.part.26+0x2a/0x760 [ 66.477005] [] _raw_spin_lock+0x36/0x50 [ 66.482619] [] ? dput.part.26+0x3b0/0x760 [ 66.488435] [] dput.part.26+0x3b0/0x760 [ 66.494057] [] ? dput.part.26+0x2a/0x760 [ 66.499765] [] dput+0x1f/0x30 [ 66.504528] [] path_put+0x31/0x70 [ 66.509628] [] free_fs_struct+0x22/0x60 [ 66.515256] [] exit_fs+0xe9/0x120 [ 66.520375] [] do_exit+0x9bf/0x26b0 [ 66.525668] [] ? __sigqueue_free.part.28+0x51/0x60 [ 66.532272] [] ? __sigqueue_free.part.28+0x51/0x60 [ 66.538926] [] ? release_task.part.17+0x1200/0x1200 [ 66.545596] [] do_group_exit+0x111/0x330 [ 66.551315] [] get_signal+0x4ec/0x14b0 [ 66.556857] [] ? force_sig_info+0x23e/0x310 [ 66.562830] [] do_signal+0x8b/0x1d30 [ 66.568197] [] ? is_prefetch.isra.20+0x390/0x390 [ 66.574608] [] ? setup_sigcontext+0x780/0x780 [ 66.580736] [] ? __lock_is_held+0xa2/0xf0 [ 66.586597] [] ? __bad_area_nosemaphore+0x21e/0x310 [ 66.593238] [] ? exit_to_usermode_loop+0xe4/0x160 [ 66.599878] [] exit_to_usermode_loop+0x11a/0x160 [ 66.606352] [] prepare_exit_to_usermode+0xe3/0x100 [ 66.612945] [] retint_user+0x8/0x3c [ 67.740531] Shutting down cpus with NMI [ 67.745126] Dumping ftrace buffer: [ 67.749547] (ftrace buffer empty) [ 67.753260] Kernel Offset: disabled [ 67.756866] Rebooting in 86400 seconds..