[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 20.450852] 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: [ 26.391916] random: sshd: uninitialized urandom read (32 bytes read, 41 bits of entropy available) [ 26.841379] random: sshd: uninitialized urandom read (32 bytes read, 41 bits of entropy available) [ 27.359208] random: sshd: uninitialized urandom read (32 bytes read, 53 bits of entropy available) [ 27.528592] random: sshd: uninitialized urandom read (32 bytes read, 55 bits of entropy available) Warning: Permanently added '10.128.0.30' (ECDSA) to the list of known hosts. [ 33.150857] random: sshd: uninitialized urandom read (32 bytes read, 60 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 [ 39.399560] ================================================================== [ 39.406946] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 39.414202] Read of size 4 at addr ffff8801d8cfc000 by task syz-executor928/5649 [ 39.421707] [ 39.423315] CPU: 1 PID: 5649 Comm: syz-executor928 Not tainted 4.4.147-ga5fc665 #16 [ 39.431081] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 39.440413] 0000000000000000 d030d8a78fd8a1c5 ffff8801cb4678b8 ffffffff81e12a4d [ 39.448426] ffffea0007633f00 ffff8801d8cfc000 0000000000000000 ffff8801d8cfc000 [ 39.456472] ffffffff82f1f9a0 ffff8801cb4678f0 ffffffff81517fd6 ffff8801d8cfc000 [ 39.464483] Call Trace: [ 39.467055] [] dump_stack+0xc1/0x124 [ 39.472402] [] ? sock_release+0x1c0/0x1c0 [ 39.478181] [] print_address_description+0x6c/0x216 [ 39.484827] [] ? sock_release+0x1c0/0x1c0 [ 39.490606] [] kasan_report.cold.7+0x175/0x2f7 [ 39.496816] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 39.503559] [] __asan_report_load4_noabort+0x14/0x20 [ 39.510291] [] l2tp_session_queue_purge+0xf4/0x100 [ 39.516873] [] ? sock_release+0x1c0/0x1c0 [ 39.522678] [] pppol2tp_release+0x1ff/0x310 [ 39.528633] [] sock_release+0x96/0x1c0 [ 39.534153] [] sock_close+0x16/0x20 [ 39.539411] [] __fput+0x235/0x6f0 [ 39.544496] [] ____fput+0x15/0x20 [ 39.549580] [] task_work_run+0x10f/0x190 [ 39.555269] [] do_exit+0x9e5/0x26b0 [ 39.560526] [] ? __sigqueue_free.part.28+0x51/0x60 [ 39.567100] [] ? __sigqueue_free.part.28+0x51/0x60 [ 39.573658] [] ? release_task.part.17+0x1200/0x1200 [ 39.580302] [] do_group_exit+0x111/0x330 [ 39.586004] [] get_signal+0x4ec/0x14b0 [ 39.591520] [] ? force_sig_info+0x23e/0x310 [ 39.597470] [] do_signal+0x8b/0x1d30 [ 39.602812] [] ? is_prefetch.isra.20+0x390/0x390 [ 39.609196] [] ? setup_sigcontext+0x780/0x780 [ 39.615322] [] ? __lock_is_held+0xa2/0xf0 [ 39.621100] [] ? __bad_area_nosemaphore+0x21e/0x310 [ 39.627743] [] ? exit_to_usermode_loop+0xe4/0x160 [ 39.634212] [] exit_to_usermode_loop+0x11a/0x160 [ 39.640595] [] prepare_exit_to_usermode+0xe3/0x100 [ 39.647166] [] retint_user+0x8/0x3c [ 39.652434] [ 39.654041] Allocated by task 5646: [ 39.657638] [] save_stack_trace+0x26/0x50 [ 39.663540] [] save_stack+0x43/0xd0 [ 39.668931] [] kasan_kmalloc+0xc7/0xe0 [ 39.674585] [] __kmalloc+0x124/0x310 [ 39.680354] [] l2tp_session_create+0x39/0x1030 [ 39.686693] [] pppol2tp_connect+0x10f0/0x1910 [ 39.692950] [] SYSC_connect+0x1b8/0x300 [ 39.698699] [] SyS_connect+0x24/0x30 [ 39.704163] [] do_fast_syscall_32+0x324/0x8b0 [ 39.710410] [] sysenter_flags_fixed+0xd/0x1a [ 39.716570] [ 39.718172] Freed by task 5625: [ 39.721422] [] save_stack_trace+0x26/0x50 [ 39.727318] [] save_stack+0x43/0xd0 [ 39.732707] [] kasan_slab_free+0x72/0xc0 [ 39.738539] [] kfree+0xf4/0x310 [ 39.743580] [] l2tp_session_free+0x170/0x200 [ 39.749740] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 39.756175] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 39.762615] [] udpv6_destroy_sock+0xb1/0xd0 [ 39.768687] [] sk_common_release+0x6d/0x300 [ 39.774765] [] udp_lib_close+0x15/0x20 [ 39.780439] [] inet_release+0xff/0x1d0 [ 39.786083] [] inet6_release+0x50/0x70 [ 39.791741] [] sock_release+0x96/0x1c0 [ 39.797372] [] sock_close+0x16/0x20 [ 39.802747] [] __fput+0x235/0x6f0 [ 39.807973] [] ____fput+0x15/0x20 [ 39.813177] [] task_work_run+0x10f/0x190 [ 39.818983] [] do_exit+0x9e5/0x26b0 [ 39.824354] [] do_group_exit+0x111/0x330 [ 39.830156] [] get_signal+0x4ec/0x14b0 [ 39.835795] [] do_signal+0x8b/0x1d30 [ 39.841256] [] exit_to_usermode_loop+0x11a/0x160 [ 39.847761] [] prepare_exit_to_usermode+0xe3/0x100 [ 39.854440] [] retint_user+0x8/0x3c [ 39.859820] [ 39.861443] The buggy address belongs to the object at ffff8801d8cfc000 [ 39.861443] which belongs to the cache kmalloc-512 of size 512 [ 39.874085] The buggy address is located 0 bytes inside of [ 39.874085] 512-byte region [ffff8801d8cfc000, ffff8801d8cfc200) [ 39.885855] The buggy address belongs to the page: [ 41.301226] PANIC: double fault, error_code: 0x0 [ 41.306063] CPU: 1 PID: 5649 Comm: syz-executor928 Not tainted 4.4.147-ga5fc665 #16 [ 41.314034] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 41.323396] task: ffff8800bae9e000 task.stack: ffff8801cb460000 [ 41.329449] RIP: 0010:[] [] dump_page_badflags+0xd/0x70 [ 41.338172] RSP: 0018:ffff880100000000 EFLAGS: 00010046 [ 41.343614] RAX: ffff8800bae9e000 RBX: ffffea0007633f00 RCX: 0000000000000000 [ 41.350897] RDX: 0000000000000000 RSI: ffffffff83aaad60 RDI: ffffea0007633f00 [ 41.358273] RBP: ffff880100000018 R08: 0000000000000001 R09: 0000000000000000 [ 41.365612] R10: 0000000000000001 R11: ffffffff858f0274 R12: 0000000000000000 [ 41.372891] R13: ffffffff83aaad60 R14: ffff8801d8cfc000 R15: ffff8801d8cfc200 [ 41.380156] FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 41.388390] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 [ 41.394266] CR2: ffff8800fffffff8 CR3: 00000000b4b83000 CR4: 00000000001606f0 [ 41.401583] Stack: [ 41.403732] [ 41.405340] Call Trace: [ 41.407909] [ 41.409947] Code: f0 48 ff 80 28 5b 9f 84 5b 5d c3 48 89 df e8 3b c9 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 01 43 ec ff 48 89 da [ 41.438422] Kernel panic - not syncing: Machine halted. [ 41.443793] CPU: 1 PID: 5649 Comm: syz-executor928 Not tainted 4.4.147-ga5fc665 #16 [ 41.451675] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 41.461016] 0000000000000000 d030d8a78fd8a1c5 ffff8801db30ce40 ffffffff81e12a4d [ 41.469081] ffffffff83a38560 0000000000000000 ffffffff83a08060 ffff880100000000 [ 41.477122] ffff8801d8cfc200 ffff8801db30cf00 ffffffff8140c6a4 0000000041b58ab3 [ 41.485185] Call Trace: [ 41.487756] <#DF> [] dump_stack+0xc1/0x124 [ 41.493967] [] panic+0x19e/0x38d Inconsistency de[ 41.498982] [] ? add_taint.cold.4+0x16/0x16 [ 41.506358] [] ? vprintk_emit+0x249/0x840 [ 41.512157] [] ? vprintk_emit+0x249/0x840 [ 41.517975] [] df_debug+0x2d/0x2d [ 41.523083] [] do_double_fault+0x113/0x230 [ 41.529249] [] double_fault+0x2d/0x40 tected by ld.so:[ 41.534747] [] ? dump_page_badflags+0xd/0x70 [ 41.542265] <> dl-fini.c: 197: [ 41.545698] Dumping ftrace buffer: [ 41.550500] (ftrace buffer empty) [ 41.554260] Kernel Offset: disabled [ 41.558067] Rebooting in 86400 seconds..