[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 16.351441] 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: [ 19.545622] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 19.868226] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 20.775562] random: sshd: uninitialized urandom read (32 bytes read, 104 bits of entropy available) [ 20.955565] random: sshd: uninitialized urandom read (32 bytes read, 109 bits of entropy available) Warning: Permanently added '10.128.15.223' (ECDSA) to the list of known hosts. [ 26.351675] random: sshd: uninitialized urandom read (32 bytes read, 116 bits of entropy available) executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 26.547725] l2tp_core: tunl 3: sockfd_lookup(fd=22) returned -9 [ 26.575238] l2tp_core: tunl 3: sockfd_lookup(fd=22) returned -9 [ 26.583214] l2tp_core: tunl 3: fd 22 wrong protocol, got 1, expected 17 executing program executing program executing program [ 26.654105] ================================================================== [ 26.661481] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xee/0x110 [ 26.668810] Read of size 4 at addr ffff8801d0d7f900 by task syzkaller200052/3311 [ 26.676309] [ 26.677910] CPU: 0 PID: 3311 Comm: syzkaller200052 Not tainted 4.4.112-g3fc4284 #32 [ 26.685671] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.694997] 0000000000000000 67bd1219ecaac6d9 ffff8801d083fc70 ffffffff81d054ed [ 26.702998] ffffea0007435f80 ffff8801d0d7f900 0000000000000000 ffff8801d0d7f900 [ 26.710982] ffffffff82dea4d0 ffff8801d083fca8 ffffffff814fd953 ffff8801d0d7f900 [ 26.718954] Call Trace: [ 26.721520] [] dump_stack+0xc1/0x124 [ 26.726855] [] ? sock_release+0x1e0/0x1e0 [ 26.732624] [] print_address_description+0x73/0x260 [ 26.739258] [] ? sock_release+0x1e0/0x1e0 [ 26.745023] [] kasan_report+0x285/0x370 [ 26.750617] [] ? pppol2tp_session_destruct+0xee/0x110 [ 26.757428] [] __asan_report_load4_noabort+0x14/0x20 [ 26.764160] [] pppol2tp_session_destruct+0xee/0x110 [ 26.770795] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 26.777084] [] sk_destruct+0x4a/0x4c0 [ 26.782504] [] __sk_free+0x57/0x230 [ 26.787753] [] sk_free+0x30/0x40 [ 26.792739] [] pppol2tp_release+0x27a/0x310 [ 26.798679] [] sock_release+0x8d/0x1e0 [ 26.804196] [] sock_close+0x16/0x20 [ 26.809444] [] __fput+0x233/0x6d0 [ 26.814516] [] ____fput+0x15/0x20 [ 26.819595] [] task_work_run+0x104/0x180 [ 26.825274] [] exit_to_usermode_loop+0x145/0x170 [ 26.831647] [] syscall_return_slowpath+0x1b5/0x1f0 [ 26.838195] [] int_ret_from_sys_call+0x25/0xa3 [ 26.844395] [ 26.845993] Allocated by task 3310: [ 26.849587] [] save_stack_trace+0x26/0x50 [ 26.855478] [] save_stack+0x43/0xd0 [ 26.860840] [] kasan_kmalloc+0xad/0xe0 [ 26.866464] [] __kmalloc+0x124/0x320 [ 26.871917] [] l2tp_session_create+0x39/0x10f0 [ 26.878233] [] pppol2tp_connect+0x10fc/0x1930 [ 26.884465] [] SYSC_connect+0x1b6/0x310 [ 26.890175] [] SyS_connect+0x24/0x30 [ 26.895638] [] entry_SYSCALL_64_fastpath+0x16/0x92 [ 26.902304] [ 26.903899] Freed by task 3310: [ 26.907143] [] save_stack_trace+0x26/0x50 [ 26.913034] [] save_stack+0x43/0xd0 [ 26.918398] [] kasan_slab_free+0x72/0xc0 [ 26.924195] [] kfree+0xfc/0x300 [ 26.929210] [] l2tp_session_free+0x170/0x200 [ 26.935357] [] l2tp_tunnel_closeall+0x2d1/0x3b0 [ 26.941759] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 26.948167] [] udpv6_destroy_sock+0xb1/0xd0 [ 26.954246] [] sk_common_release+0x6b/0x300 [ 26.960316] [] udp_lib_close+0x15/0x20 [ 26.965940] [] inet_release+0xfa/0x1d0 [ 26.971566] [] inet6_release+0x50/0x70 [ 26.977191] [] sock_release+0x8d/0x1e0 [ 26.982815] [] sock_close+0x16/0x20 [ 26.988178] [] __fput+0x233/0x6d0 [ 26.993367] [] ____fput+0x15/0x20 [ 26.998556] [] task_work_run+0x104/0x180 [ 27.004352] [] exit_to_usermode_loop+0x145/0x170 [ 27.010844] [] syscall_return_slowpath+0x1b5/0x1f0 [ 27.017512] [] int_ret_from_sys_call+0x25/0xa3 [ 27.023831] [ 27.025430] The buggy address belongs to the object at ffff8801d0d7f900 [ 27.025430] which belongs to the cache kmalloc-512 of size 512 [ 27.038056] The buggy address is located 0 bytes inside of [ 27.038056] 512-byte region [ffff8801d0d7f900, ffff8801d0d7fb00) [ 27.049724] The buggy address belongs to the page: [ 28.586239] PANIC: double fault, error_code: 0x0 [ 28.591035] CPU: 0 PID: 3311 Comm: syzkaller200052 Not tainted 4.4.112-g3fc4284 #32 [ 28.598797] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.608122] task: ffff8801d0db0000 task.stack: ffff8801d0838000 [ 28.614149] RIP: 0010:[] [] dump_page_badflags+0x8/0x250 [ 28.622917] RSP: 0018:ffff880100000000 EFLAGS: 00010046 [ 28.628336] RAX: ffff8801d0db0000 RBX: ffffea0007435f80 RCX: ffffffff8148fea0 [ 28.635581] RDX: 0000000000000000 RSI: ffffffff838a8620 RDI: ffffea0007435f80 [ 28.642822] RBP: ffff880100000010 R08: 0000000000000001 R09: 0000000000000000 [ 28.650064] R10: 0000000000000002 R11: fffffbfff0ad7a1e R12: 0000000000000000 [ 28.657316] R13: ffffffff838a8620 R14: 0000000000000000 R15: 0000000000000000 [ 28.664559] FS: 00007fcf99da9700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 28.672753] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 28.678606] CR2: ffff8800fffffff8 CR3: 00000001d2330000 CR4: 0000000000160670 [ 28.685850] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 28.693100] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 28.700341] Stack: [ 28.702460] [ 28.704057] Call Trace: [ 28.706617] [ 28.708647] Code: 00 e9 83 fd ff ff e8 a8 e2 06 00 e9 50 fd ff ff e8 9e e2 06 00 e9 1d fd ff ff 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 01 [ 28.735760] Kernel panic - not syncing: Machine halted. [ 28.741093] CPU: 0 PID: 3311 Comm: syzkaller200052 Not tainted 4.4.112-g3fc4284 #32 [ 28.748855] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.758178] 0000000000000000 67bd1219ecaac6d9 ffff8801db20ce38 ffffffff81d054ed [ 28.766149] ffffffff83836a60 ffff8801db20cf10 ffffffff83808040 ffff880100000000 [ 28.774129] 0000000000000000 ffff8801db20cf00 ffffffff81419dca 0000000041b58ab3 [ 28.782098] Call Trace: [ 28.784650] <#DF> [] dump_stack+0xc1/0x124 [ 28.790719] [] panic+0x1aa/0x388 [ 28.795705] [] ? percpu_up_read.constprop.45+0xe1/0xe1 [ 28.802603] [] ? vprintk_emit+0x242/0x850 [ 28.808372] [] ? dump_page_badflags+0x1d/0x250 [ 28.814574] [] ? vprintk_emit+0x242/0x850 [ 28.820348] [] df_debug+0x2d/0x30 [ 28.825424] [] do_double_fault+0x10b/0x210 [ 28.831279] [] double_fault+0x2d/0x40 [ 28.836704] [] ? dump_page_badflags+0x180/0x250 [ 28.842999] [] ? dump_page_badflags+0x8/0x250 [ 28.849109] <> [ 28.852510] Dumping ftrace buffer: [ 28.856352] (ftrace buffer empty) [ 28.860030] Kernel Offset: disabled [ 28.863635] Rebooting in 86400 seconds..