[ 16.719839] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 20.427172] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 20.786447] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 21.678422] random: sshd: uninitialized urandom read (32 bytes read, 105 bits of entropy available) [ 21.883656] random: sshd: uninitialized urandom read (32 bytes read, 115 bits of entropy available) Warning: Permanently added '10.128.15.231' (ECDSA) to the list of known hosts. [ 27.292706] random: sshd: uninitialized urandom read (32 bytes read, 125 bits of entropy available) executing program executing program executing program executing program [ 27.427121] ================================================================== [ 27.434508] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xee/0x110 [ 27.441839] Read of size 4 at addr ffff8801d0e98f00 by task syzkaller717112/3336 [ 27.449352] [ 27.450956] CPU: 1 PID: 3336 Comm: syzkaller717112 Not tainted 4.4.112-g3fc4284 #32 [ 27.458723] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.468059] 0000000000000000 27f87a603c5d43e7 ffff8801d07ffc70 ffffffff81d054ed [ 27.476079] ffffea000743a600 ffff8801d0e98f00 0000000000000000 ffff8801d0e98f00 [ 27.484093] ffffffff82dea4d0 ffff8801d07ffca8 ffffffff814fd953 ffff8801d0e98f00 [ 27.492100] Call Trace: [ 27.494672] [] dump_stack+0xc1/0x124 [ 27.500023] [] ? sock_release+0x1e0/0x1e0 [ 27.505808] [] print_address_description+0x73/0x260 [ 27.512462] [] ? sock_release+0x1e0/0x1e0 [ 27.518258] [] kasan_report+0x285/0x370 [ 27.523875] [] ? pppol2tp_session_destruct+0xee/0x110 [ 27.530707] [] __asan_report_load4_noabort+0x14/0x20 [ 27.537448] [] pppol2tp_session_destruct+0xee/0x110 [ 27.544110] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 27.550419] [] sk_destruct+0x4a/0x4c0 [ 27.555860] [] __sk_free+0x57/0x230 [ 27.561110] [] sk_free+0x30/0x40 [ 27.566107] [] pppol2tp_release+0x27a/0x310 [ 27.572056] [] sock_release+0x8d/0x1e0 [ 27.577573] [] sock_close+0x16/0x20 [ 27.582832] [] __fput+0x233/0x6d0 [ 27.587911] [] ____fput+0x15/0x20 [ 27.592984] [] task_work_run+0x104/0x180 [ 27.598665] [] exit_to_usermode_loop+0x145/0x170 [ 27.605042] [] syscall_return_slowpath+0x1b5/0x1f0 [ 27.611590] [] int_ret_from_sys_call+0x25/0xa3 [ 27.617788] [ 27.619384] Allocated by task 3335: [ 27.622982] [] save_stack_trace+0x26/0x50 [ 27.628873] [] save_stack+0x43/0xd0 [ 27.634236] [] kasan_kmalloc+0xad/0xe0 [ 27.639864] [] __kmalloc+0x124/0x320 [ 27.645320] [] l2tp_session_create+0x39/0x10f0 [ 27.651653] [] pppol2tp_connect+0x10fc/0x1930 [ 27.657901] [] SYSC_connect+0x1b6/0x310 [ 27.663619] [] SyS_connect+0x24/0x30 [ 27.669075] [] entry_SYSCALL_64_fastpath+0x16/0x92 [ 27.675748] [ 27.677347] Freed by task 3335: [ 27.680592] [] save_stack_trace+0x26/0x50 [ 27.686485] [] save_stack+0x43/0xd0 [ 27.691853] [] kasan_slab_free+0x72/0xc0 [ 27.697650] [] kfree+0xfc/0x300 [ 27.702662] [] l2tp_session_free+0x170/0x200 [ 27.708809] [] l2tp_tunnel_closeall+0x2d1/0x3b0 [ 27.715214] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 27.721620] [] udpv6_destroy_sock+0xb1/0xd0 [ 27.727690] [] sk_common_release+0x6b/0x300 [ 27.733747] [] udp_lib_close+0x15/0x20 [ 27.739382] [] inet_release+0xfa/0x1d0 [ 27.745014] [] inet6_release+0x50/0x70 [ 27.750652] [] sock_release+0x8d/0x1e0 [ 27.756278] [] sock_close+0x16/0x20 [ 27.761642] [] __fput+0x233/0x6d0 [ 27.766831] [] ____fput+0x15/0x20 [ 27.772025] [] task_work_run+0x104/0x180 [ 27.777823] [] exit_to_usermode_loop+0x145/0x170 [ 27.784320] [] syscall_return_slowpath+0x1b5/0x1f0 [ 27.790999] [] int_ret_from_sys_call+0x25/0xa3 [ 27.797320] [ 27.798919] The buggy address belongs to the object at ffff8801d0e98f00 [ 27.798919] which belongs to the cache kmalloc-512 of size 512 [ 27.811549] The buggy address is located 0 bytes inside of [ 27.811549] 512-byte region [ffff8801d0e98f00, ffff8801d0e99100) [ 27.823228] The buggy address belongs to the page: [ 29.389403] PANIC: double fault, error_code: 0x0 [ 29.394196] CPU: 1 PID: 3336 Comm: syzkaller717112 Not tainted 4.4.112-g3fc4284 #32 [ 29.401958] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.411303] task: ffff8800b428df00 task.stack: ffff8801d07f8000 [ 29.417330] RIP: 0010:[] [] dump_page_badflags+0x8/0x250 [ 29.426091] RSP: 0018:ffff880100000000 EFLAGS: 00010046 [ 29.431509] RAX: ffff8800b428df00 RBX: ffffea000743a600 RCX: ffffffff8148fea0 [ 29.438748] RDX: 0000000000000000 RSI: ffffffff838a8620 RDI: ffffea000743a600 [ 29.445986] RBP: ffff880100000010 R08: 0000000000000001 R09: 0000000000000000 [ 29.453236] R10: 0000000000000002 R11: fffffbfff0ad7a1e R12: 0000000000000000 [ 29.460476] R13: ffffffff838a8620 R14: 0000000000000000 R15: 0000000000000000 [ 29.467717] FS: 00007f1673ed2700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 29.475918] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 29.481777] CR2: ffff8800fffffff8 CR3: 00000001d0b7c000 CR4: 0000000000160670 [ 29.489020] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 29.496259] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 29.503498] Stack: [ 29.505615] [ 29.507208] Call Trace: [ 29.509757] [ 29.511785] 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 [ 29.538717] Kernel panic - not syncing: Machine halted. [ 29.544064] CPU: 1 PID: 3336 Comm: syzkaller717112 Not tainted 4.4.112-g3fc4284 #32 [ 29.551831] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.561167] 0000000000000000 27f87a603c5d43e7 ffff8801db30ce38 ffffffff81d054ed [ 29.569169] ffffffff83836a60 ffff8801db30cf10 ffffffff83808040 ffff880100000000 [ 29.577160] 0000000000000000 ffff8801db30cf00 ffffffff81419dca 0000000041b58ab3 [ 29.585157] Call Trace: [ 29.587717] <#DF> [] dump_stack+0xc1/0x124 [ 29.593794] [] panic+0x1aa/0x388 [ 29.598795] [] ? percpu_up_read.constprop.45+0xe1/0xe1 [ 29.605702] [] ? vprintk_emit+0x242/0x850 [ 29.611471] [] ? dump_page_badflags+0x1d/0x250 [ 29.617672] [] ? vprintk_emit+0x242/0x850 [ 29.623446] [] df_debug+0x2d/0x30 [ 29.628536] [] do_double_fault+0x10b/0x210 [ 29.634391] [] double_fault+0x2d/0x40 [ 29.639809] [] ? dump_page_badflags+0x180/0x250 [ 29.646099] [] ? dump_page_badflags+0x8/0x250 [ 29.652226] <> [ 29.655685] Dumping ftrace buffer: [ 29.659532] (ftrace buffer empty) [ 29.663213] Kernel Offset: disabled [ 29.666825] Rebooting in 86400 seconds..