[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.817636] random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 24.866634] random: sshd: uninitialized urandom read (32 bytes read, 36 bits of entropy available) [ 25.402009] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 26.382805] random: nonblocking pool is initialized Warning: Permanently added '10.128.10.18' (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 [ 33.191304] ================================================================== [ 33.198706] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 33.205964] Read of size 4 at addr ffff8800b485c000 by task syz-executor090/3935 [ 33.213467] [ 33.215072] CPU: 0 PID: 3935 Comm: syz-executor090 Not tainted 4.4.132-g46155cc #42 [ 33.222836] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 33.232164] 0000000000000000 b66fa59aa0604ae8 ffff8801cc567b50 ffffffff81e0df8d [ 33.240159] ffffea0002d21700 ffff8800b485c000 0000000000000000 ffff8800b485c000 [ 33.248152] ffffffff82f18e30 ffff8801cc567b88 ffffffff8151526c ffff8800b485c000 [ 33.256142] Call Trace: [ 33.258706] [] dump_stack+0xc1/0x124 [ 33.264060] [] ? sock_release+0x1c0/0x1c0 [ 33.269832] [] print_address_description+0x6c/0x216 [ 33.276469] [] ? sock_release+0x1c0/0x1c0 [ 33.282241] [] kasan_report.cold.7+0x175/0x2f7 [ 33.288445] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 33.295174] [] __asan_report_load4_noabort+0x14/0x20 [ 33.301899] [] l2tp_session_queue_purge+0xf4/0x100 [ 33.308449] [] ? sock_release+0x1c0/0x1c0 [ 33.314222] [] pppol2tp_release+0x1ff/0x310 [ 33.320166] [] sock_release+0x96/0x1c0 [ 33.325677] [] sock_close+0x16/0x20 [ 33.330937] [] __fput+0x235/0x6f0 [ 33.336033] [] ____fput+0x15/0x20 [ 33.341110] [] task_work_run+0x10f/0x190 [ 33.346800] [] do_exit+0x9e5/0x26b0 [ 33.352051] [] ? release_task.part.17+0x1200/0x1200 [ 33.358692] [] ? __do_page_fault+0x385/0xa10 [ 33.364727] [] ? retint_user+0x18/0x3c [ 33.370238] [] do_group_exit+0x111/0x330 [ 33.375923] [] ? trace_hardirqs_on_thunk+0x17/0x19 [ 33.382474] [] SyS_exit_group+0x1d/0x20 [ 33.388073] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 33.394621] [ 33.396224] Allocated by task 3933: [ 33.399820] [] save_stack_trace+0x26/0x50 [ 33.405714] [] save_stack+0x43/0xd0 [ 33.411085] [] kasan_kmalloc+0xc7/0xe0 [ 33.416715] [] __kmalloc+0x124/0x310 [ 33.422173] [] l2tp_session_create+0x39/0x1030 [ 33.428501] [] pppol2tp_connect+0x10f0/0x1910 [ 33.434745] [] SYSC_connect+0x1b8/0x300 [ 33.440463] [] SyS_connect+0x24/0x30 [ 33.445920] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 33.452591] [ 33.454223] Freed by task 3900: [ 33.457479] [] save_stack_trace+0x26/0x50 [ 33.463372] [] save_stack+0x43/0xd0 [ 33.468739] [] kasan_slab_free+0x72/0xc0 [ 33.474543] [] kfree+0xf4/0x310 [ 33.479565] [] l2tp_session_free+0x170/0x200 [ 33.485718] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 33.492137] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 33.498551] [] udpv6_destroy_sock+0xb1/0xd0 [ 33.504615] [] sk_common_release+0x6d/0x300 [ 33.510943] [] udp_lib_close+0x15/0x20 [ 33.516587] [] inet_release+0xff/0x1d0 [ 33.522222] [] inet6_release+0x50/0x70 [ 33.527853] [] sock_release+0x96/0x1c0 [ 33.533485] [] sock_close+0x16/0x20 [ 33.538855] [] __fput+0x235/0x6f0 [ 33.544061] [] ____fput+0x15/0x20 [ 33.549256] [] task_work_run+0x10f/0x190 [ 33.555061] [] do_exit+0x9e5/0x26b0 [ 33.560429] [] do_group_exit+0x111/0x330 [ 33.566235] [] SyS_exit_group+0x1d/0x20 [ 33.571949] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 33.578641] [ 33.580244] The buggy address belongs to the object at ffff8800b485c000 [ 33.580244] which belongs to the cache kmalloc-512 of size 512 [ 33.592884] The buggy address is located 0 bytes inside of [ 33.592884] 512-byte region [ffff8800b485c000, ffff8800b485c200) [ 33.604554] The buggy address belongs to the page: [ 35.251256] PANIC: double fault, error_code: 0x0 [ 35.256050] CPU: 0 PID: 3935 Comm: syz-executor090 Not tainted 4.4.132-g46155cc #42 [ 35.263817] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 35.273146] task: ffff8801cdc98000 task.stack: ffff8801cc560000 [ 35.279178] RIP: 0010:[] [] dump_page_badflags+0x1a/0x70 [ 35.287942] RSP: 0000:ffff880100000000 EFLAGS: 00010086 [ 35.293365] RAX: ffff8801cdc98000 RBX: ffffea0002d21700 RCX: 0000000000000000 [ 35.300609] RDX: 0000000000000000 RSI: ffffffff83aa9be0 RDI: ffffea0002d21700 [ 35.307862] RBP: ffff880100000030 R08: 0000000000000001 R09: 0000000000000000 [ 35.315115] R10: 0000000000000001 R11: ffffffff858ed134 R12: 0000000000000000 [ 35.322358] R13: ffffffff83aa9be0 R14: ffff8800b485c000 R15: ffff8800b485c200 [ 35.329605] FS: 00007f5419132700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 35.337812] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 35.343667] CR2: ffff8800fffffff8 CR3: 00000000b1260000 CR4: 00000000001606f0 [ 35.350924] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 35.358169] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 35.365410] Stack: [ 35.367633] [ 35.369233] Call Trace: [ 35.371789] [ 35.373822] Code: df e8 2b c7 06 00 eb dd 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 49 89 f5 41 54 49 89 d4 53 48 89 fb 48 83 ec 08 71 48 ec ff 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea [ 35.401223] Kernel panic - not syncing: Machine halted. [ 35.406561] CPU: 0 PID: 3935 Comm: syz-executor090 Not tainted 4.4.132-g46155cc #42 [ 35.414326] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 35.423652] 0000000000000000 b66fa59aa0604ae8 ffff8801db20ce40 ffffffff81e0df8d [ 35.431641] ffffffff83a376e0 0000000000000000 ffffffff83a08060 ffff880100000000 [ 35.439636] ffff8800b485c200 ffff8801db20cf00 ffffffff81409de4 0000000041b58ab3 [ 35.447626] Call Trace: [ 35.450180] <#DF> [] dump_stack+0xc1/0x124 [ 35.456254] [] panic+0x19e/0x38d [ 35.461244] [] ? add_taint.cold.4+0x16/0x16 [ 35.467211] [] ? vprintk_emit+0x249/0x840 [ 35.472991] [] ? vprintk_emit+0x249/0x840 [ 35.478768] [] df_debug+0x2d/0x2d [ 35.483846] [] do_double_fault+0x113/0x230 [ 35.489705] [] double_fault+0x2d/0x40 [ 35.495132] [] ? dump_page_badflags+0x1a/0x70 [ 35.501258] <> [ 35.504939] Dumping ftrace buffer: [ 35.508788] (ftrace buffer empty) [ 35.512474] Kernel Offset: disabled [ 35.516083] Rebooting in 86400 seconds..