[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.968092] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 23.604723] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 23.751757] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 24.510460] random: sshd: uninitialized urandom read (32 bytes read, 73 bits of entropy available) [ 52.903844] random: sshd: uninitialized urandom read (32 bytes read, 85 bits of entropy available) Warning: Permanently added '10.128.10.17' (ECDSA) to the list of known hosts. [ 58.500413] random: sshd: uninitialized urandom read (32 bytes read, 93 bits of entropy available) executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 74.187314] ================================================================== [ 74.194747] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 74.202003] Read of size 4 at addr ffff8801d7717900 by task syz-executor661/6947 [ 74.209514] [ 74.211129] CPU: 0 PID: 6947 Comm: syz-executor661 Not tainted 4.4.147-ga5fc665 #80 [ 74.218914] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 74.228365] 0000000000000000 36ac9e711a25615f ffff8801d6a378b8 ffffffff81e12a4d [ 74.236368] ffffea00075dc580 ffff8801d7717900 0000000000000000 ffff8801d7717900 [ 74.244457] ffffffff82f1f9a0 ffff8801d6a378f0 ffffffff81517fd6 ffff8801d7717900 [ 74.252494] Call Trace: [ 74.255063] [] dump_stack+0xc1/0x124 [ 74.260410] [] ? sock_release+0x1c0/0x1c0 [ 74.266192] [] print_address_description+0x6c/0x216 [ 74.272842] [] ? sock_release+0x1c0/0x1c0 [ 74.278621] [] kasan_report.cold.7+0x175/0x2f7 [ 74.284837] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 74.291625] [] __asan_report_load4_noabort+0x14/0x20 [ 74.298648] [] l2tp_session_queue_purge+0xf4/0x100 [ 74.305269] [] ? sock_release+0x1c0/0x1c0 [ 74.311059] [] pppol2tp_release+0x1ff/0x310 [ 74.317009] [] sock_release+0x96/0x1c0 [ 74.322525] [] sock_close+0x16/0x20 [ 74.327780] [] __fput+0x235/0x6f0 [ 74.332862] [] ____fput+0x15/0x20 [ 74.337951] [] task_work_run+0x10f/0x190 [ 74.343653] [] do_exit+0x9e5/0x26b0 [ 74.348911] [] ? __sigqueue_free.part.28+0x51/0x60 [ 74.355641] [] ? __sigqueue_free.part.28+0x51/0x60 [ 74.362249] [] ? release_task.part.17+0x1200/0x1200 [ 74.368903] [] do_group_exit+0x111/0x330 [ 74.374595] [] get_signal+0x4ec/0x14b0 [ 74.380115] [] ? force_sig_info+0x23e/0x310 [ 74.386073] [] do_signal+0x8b/0x1d30 [ 74.391416] [] ? is_prefetch.isra.20+0x390/0x390 [ 74.397800] [] ? setup_sigcontext+0x780/0x780 [ 74.403925] [] ? __lock_is_held+0xa2/0xf0 [ 74.409701] [] ? __bad_area_nosemaphore+0x21e/0x310 [ 74.416342] [] ? exit_to_usermode_loop+0xe4/0x160 [ 74.422823] [] exit_to_usermode_loop+0x11a/0x160 [ 74.429208] [] prepare_exit_to_usermode+0xe3/0x100 [ 74.435774] [] retint_user+0x8/0x3c [ 74.441050] [ 74.442704] Allocated by task 6943: [ 74.446312] [] save_stack_trace+0x26/0x50 [ 74.452213] [] save_stack+0x43/0xd0 [ 74.457611] [] kasan_kmalloc+0xc7/0xe0 [ 74.463270] [] __kmalloc+0x124/0x310 [ 74.468736] [] l2tp_session_create+0x39/0x1030 [ 74.475096] [] pppol2tp_connect+0x10f0/0x1910 [ 74.481350] [] SYSC_connect+0x1b8/0x300 [ 74.487082] [] SyS_connect+0x24/0x30 [ 74.492547] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 74.499242] [ 74.500848] Freed by task 6913: [ 74.504106] [] save_stack_trace+0x26/0x50 [ 74.510007] [] save_stack+0x43/0xd0 [ 74.515386] [] kasan_slab_free+0x72/0xc0 [ 74.521206] [] kfree+0xf4/0x310 [ 74.526242] [] l2tp_session_free+0x170/0x200 [ 74.532421] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 74.538847] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 74.545266] [] udpv6_destroy_sock+0xb1/0xd0 [ 74.551344] [] sk_common_release+0x6d/0x300 [ 74.557417] [] udp_lib_close+0x15/0x20 [ 74.563113] [] inet_release+0xff/0x1d0 [ 74.568766] [] inet6_release+0x50/0x70 [ 74.574404] [] sock_release+0x96/0x1c0 [ 74.580042] [] sock_close+0x16/0x20 [ 74.585419] [] __fput+0x235/0x6f0 [ 74.590626] [] ____fput+0x15/0x20 [ 74.595829] [] task_work_run+0x10f/0x190 [ 74.601643] [] do_exit+0x9e5/0x26b0 [ 74.607026] [] do_group_exit+0x111/0x330 [ 74.612842] [] get_signal+0x4ec/0x14b0 [ 74.618481] [] do_signal+0x8b/0x1d30 [ 74.623945] [] exit_to_usermode_loop+0x11a/0x160 [ 74.630453] [] prepare_exit_to_usermode+0xe3/0x100 [ 74.637141] [] retint_user+0x8/0x3c [ 74.642525] [ 74.644143] The buggy address belongs to the object at ffff8801d7717900 [ 74.644143] which belongs to the cache kmalloc-512 of size 512 [ 74.656776] The buggy address is located 0 bytes inside of [ 74.656776] 512-byte region [ffff8801d7717900, ffff8801d7717b00) [ 74.668448] The buggy address belongs to the page: [ 74.683617] ------------[ cut here ]------------ [ 74.688413] WARNING: CPU: 1 PID: 3835 at kernel/sched/core.c:7946 __might_sleep+0x138/0x1a0() [ 74.697119] do not call blocking ops when !TASK_RUNNING; state=1 set at [] do_nanosleep+0x102/0x4f0 [ 74.707875] Kernel panic - not syncing: panic_on_warn set ... [ 74.707875] [ 75.836015] Shutting down cpus with NMI [ 75.840336] Dumping ftrace buffer: [ 75.843907] (ftrace buffer empty) [ 75.847598] Kernel Offset: disabled [ 75.851202] Rebooting in 86400 seconds..