[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[   20.709223] 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: [   31.817735] random: sshd: uninitialized urandom read (32 bytes read, 39 bits of entropy available)
[   32.353735] random: sshd: uninitialized urandom read (32 bytes read, 39 bits of entropy available)
[   33.279104] random: sshd: uninitialized urandom read (32 bytes read, 112 bits of entropy available)
[   33.436344] random: sshd: uninitialized urandom read (32 bytes read, 114 bits of entropy available)
Warning: Permanently added '10.128.0.54' (ECDSA) to the list of known hosts.
[   38.881250] random: sshd: uninitialized urandom read (32 bytes read, 120 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
[   44.065585] random: nonblocking pool is initialized
[   44.153019] ==================================================================
[   44.160437] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100
[   44.167700] Read of size 4 at addr ffff8800b525aa00 by task syz-executor527/4032
[   44.175204] 
[   44.176808] CPU: 1 PID: 4032 Comm: syz-executor527 Not tainted 4.4.141-g8ddb600 #76
[   44.184575] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   44.193947]  0000000000000000 c286931854bfd17c ffff8801c6d37cc0 ffffffff81e1002d
[   44.202008]  ffffea0002d49680 ffff8800b525aa00 0000000000000000 ffff8800b525aa00
[   44.210067]  ffffffff82f1c220 ffff8801c6d37cf8 ffffffff81515ae6 ffff8800b525aa00
[   44.218088] Call Trace:
[   44.220689]  [<ffffffff81e1002d>] dump_stack+0xc1/0x124
[   44.226056]  [<ffffffff82f1c220>] ? sock_release+0x1c0/0x1c0
[   44.231845]  [<ffffffff81515ae6>] print_address_description+0x6c/0x216
[   44.238489]  [<ffffffff82f1c220>] ? sock_release+0x1c0/0x1c0
[   44.244280]  [<ffffffff81515e05>] kasan_report.cold.7+0x175/0x2f7
[   44.250499]  [<ffffffff8359d1c4>] ? l2tp_session_queue_purge+0xf4/0x100
[   44.257250]  [<ffffffff814f98d4>] __asan_report_load4_noabort+0x14/0x20
[   44.263995]  [<ffffffff8359d1c4>] l2tp_session_queue_purge+0xf4/0x100
[   44.270566]  [<ffffffff82f1c220>] ? sock_release+0x1c0/0x1c0
[   44.276339]  [<ffffffff835a9cff>] pppol2tp_release+0x1ff/0x310
[   44.282379]  [<ffffffff82f1c0f6>] sock_release+0x96/0x1c0
[   44.287891]  [<ffffffff82f1c236>] sock_close+0x16/0x20
[   44.293143]  [<ffffffff81522ed5>] __fput+0x235/0x6f0
[   44.298220]  [<ffffffff81523415>] ____fput+0x15/0x20
[   44.303305]  [<ffffffff8118bdbf>] task_work_run+0x10f/0x190
[   44.309172]  [<ffffffff8100362d>] exit_to_usermode_loop+0x13d/0x160
[   44.315563]  [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0
[   44.322129]  [<ffffffff838c4d35>] int_ret_from_sys_call+0x25/0xa3
[   44.328329] 
[   44.329941] Allocated by task 4033:
[   44.333538]  [<ffffffff81033c86>] save_stack_trace+0x26/0x50
[   44.339451]  [<ffffffff814f89a3>] save_stack+0x43/0xd0
[   44.344816]  [<ffffffff814f8c87>] kasan_kmalloc+0xc7/0xe0
[   44.350456]  [<ffffffff814f53a4>] __kmalloc+0x124/0x310
[   44.355917]  [<ffffffff835a2609>] l2tp_session_create+0x39/0x1030
[   44.362340]  [<ffffffff835a7310>] pppol2tp_connect+0x10f0/0x1910
[   44.368586]  [<ffffffff82f20b18>] SYSC_connect+0x1b8/0x300
[   44.374308]  [<ffffffff82f23454>] SyS_connect+0x24/0x30
[   44.379773]  [<ffffffff838c4ba5>] entry_SYSCALL_64_fastpath+0x22/0x9e
[   44.386479] 
[   44.388089] Freed by task 4033:
[   44.391336]  [<ffffffff81033c86>] save_stack_trace+0x26/0x50
[   44.397232]  [<ffffffff814f89a3>] save_stack+0x43/0xd0
[   44.402614]  [<ffffffff814f92d2>] kasan_slab_free+0x72/0xc0
[   44.408425]  [<ffffffff814f67d4>] kfree+0xf4/0x310
[   44.413470]  [<ffffffff8359f570>] l2tp_session_free+0x170/0x200
[   44.419620]  [<ffffffff835a1929>] l2tp_tunnel_closeall+0x2b9/0x350
[   44.426030]  [<ffffffff835a243b>] l2tp_udp_encap_destroy+0x8b/0xf0
[   44.432450]  [<ffffffff83494761>] udpv6_destroy_sock+0xb1/0xd0
[   44.438511]  [<ffffffff82f319cd>] sk_common_release+0x6d/0x300
[   44.444600]  [<ffffffff83493415>] udp_lib_close+0x15/0x20
[   44.450230]  [<ffffffff832faecf>] inet_release+0xff/0x1d0
[   44.455874]  [<ffffffff8341db40>] inet6_release+0x50/0x70
[   44.461504]  [<ffffffff82f1c0f6>] sock_release+0x96/0x1c0
[   44.467157]  [<ffffffff82f1c236>] sock_close+0x16/0x20
[   44.472548]  [<ffffffff81522ed5>] __fput+0x235/0x6f0
[   44.477772]  [<ffffffff81523415>] ____fput+0x15/0x20
[   44.482971]  [<ffffffff8118bdbf>] task_work_run+0x10f/0x190
[   44.488776]  [<ffffffff8100362d>] exit_to_usermode_loop+0x13d/0x160
[   44.495291]  [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0
[   44.501977]  [<ffffffff838c4d35>] int_ret_from_sys_call+0x25/0xa3
[   44.508319] 
[   44.509923] The buggy address belongs to the object at ffff8800b525aa00
[   44.509923]  which belongs to the cache kmalloc-512 of size 512
[   44.522563] The buggy address is located 0 bytes inside of
[   44.522563]  512-byte region [ffff8800b525aa00, ffff8800b525ac00)
[   44.534240] The buggy address belongs to the page:
[   46.001180] PANIC: double fault, error_code: 0x0
[   46.006077] CPU: 1 PID: 4032 Comm: syz-executor527 Not tainted 4.4.141-g8ddb600 #76
[   46.013948] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   46.023306] task: ffff8801d8fe1800 task.stack: ffff8801c6d30000
[   46.029353] RIP: 0010:[<ffffffff8148d002>]  [<ffffffff8148d002>] dump_page_badflags+0x12/0x70
[   46.038495] RSP: 0018:ffff880100000000  EFLAGS: 00010046
[   46.043931] RAX: ffff8801d8fe1800 RBX: ffffea0002d49680 RCX: 0000000000000000
[   46.051209] RDX: 0000000000000000 RSI: ffffffff83aaa220 RDI: ffffea0002d49680
[   46.058468] RBP: ffff880100000020 R08: 0000000000000001 R09: 0000000000000000
[   46.065724] R10: 0000000000000001 R11: ffffffff858ed134 R12: 0000000000000000
[   46.072979] R13: ffffffff83aaa220 R14: ffff8800b525aa00 R15: ffff8800b525ac00
[   46.080238] FS:  0000000002352880(0063) GS:ffff8801db300000(0000) knlGS:0000000000000000
[   46.088458] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   46.094317] CR2: ffff8800fffffff8 CR3: 00000001c8672000 CR4: 00000000001606f0
[   46.101581] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   46.108843] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   46.116089] Stack:
[   46.118209] 
[   46.119810] Call Trace:
[   46.122363]  <UNK> 
[   46.124397] Code: 47 9f 84 5b 5d c3 48 89 df e8 fb c8 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 e8 11 45 ec ff 48 89 da 48 b8 00 00 00 
[   46.152110] Kernel panic - not syncing: Machine halted.
[   46.157465] CPU: 1 PID: 4032 Comm: syz-executor527 Not tainted 4.4.141-g8ddb600 #76
[   46.165240] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   46.174571]  0000000000000000 c286931854bfd17c ffff8801db30ce40 ffffffff81e1002d
[   46.182575]  ffffffff83a37a20 0000000000000000 ffffffff83a08060 ffff880100000000
[   46.190582]  ffff8800b525ac00 ffff8801db30cf00 ffffffff8140a1f4 0000000041b58ab3
[   46.198607] Call Trace:
[   46.201175]  <#DF>  [<ffffffff81e1002d>] dump_stack+0xc1/0x124
[   46.207265]  [<ffffffff8140a1f4>] panic+0x19e/0x38d
[   46.212358]  [<ffffffff8140a056>] ? add_taint.cold.4+0x16/0x16
[   46.218326]  [<ffffffff8125d2b9>] ? vprintk_emit+0x249/0x840
[   46.224104]  [<ffffffff8125d2b9>] ? vprintk_emit+0x249/0x840
[   46.229888]  [<ffffffff811217d4>] df_debug+0x2d/0x2d
[   46.234976]  [<ffffffff81012023>] do_double_fault+0x113/0x230
[   46.240848]  [<ffffffff838c5c7d>] double_fault+0x2d/0x40
[   46.246297]  [<ffffffff8148d002>] ? dump_page_badflags+0x12/0x70
[   46.252423]  <<EOE>>  <UNK> 
[   46.255989] Dumping ftrace buffer:
[   46.259902]    (ftrace buffer empty)
[   46.263616] Kernel Offset: disabled
[   46.267247] Rebooting in 86400 seconds..