[....] Starting enhanced syslogd: rsyslogd[ 13.028925] audit: type=1400 audit(1519433691.095:4): avc: denied { syslog } for pid=3587 comm="rsyslogd" capability=34 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=capability2 permissive=1 [?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.15.194' (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 executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 26.997478] ================================================================== [ 26.998300] ------------[ cut here ]------------ [ 26.998305] kernel BUG at net/l2tp/l2tp_core.c:1405! [ 26.998311] invalid opcode: 0000 [#1] PREEMPT SMP KASAN [ 26.998316] Dumping ftrace buffer: [ 26.998320] (ftrace buffer empty) [ 26.998324] Modules linked in: [ 26.998331] CPU: 1 PID: 3753 Comm: syzkaller699220 Not tainted 4.9.83-g72766d7 #50 [ 26.998334] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.998338] task: ffff8801b9d99800 task.stack: ffff8801c1df0000 [ 26.998354] RIP: 0010:[] [] l2tp_tunnel_free+0xcd/0x110 [ 26.998358] RSP: 0018:ffff8801c1df7b18 EFLAGS: 00010293 [ 26.998362] RAX: ffff8801b9d99800 RBX: ffff8801c85d9400 RCX: ffffffff8358043d [ 26.998365] RDX: 0000000000000000 RSI: ffff8801c85d9580 RDI: ffff8801c85d9580 [ 26.998369] RBP: ffff8801c1df7b20 R08: 0000000000000001 R09: 0000000000000000 [ 26.998372] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c85d9400 [ 26.998376] R13: ffff8801bd54f408 R14: ffff8801d6293980 R15: 1ffff100383bef75 [ 26.998381] FS: 0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f76ffb40 [ 26.998384] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 [ 26.998387] CR2: 00000000207e8ff8 CR3: 00000001bf9de000 CR4: 0000000000160670 [ 26.998393] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 26.998396] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 26.998398] Stack: [ 26.998408] ffff8801bd54f400 ffff8801c1df7b50 ffffffff8358575d ffff8801bd54f400 [ 26.998417] ffff8801d70eb300 00000000ffffffef ffff8801c85d9400 ffff8801c1df7d10 [ 26.998426] ffffffff8358deea ffff8801c1df7ca8 00000112c4b9cbd0 ffff880100000002 [ 26.998427] Call Trace: [ 26.998435] [] l2tp_session_free+0x18d/0x200 [ 26.998443] [] pppol2tp_connect+0x108a/0x18f0 [ 26.998450] [] ? pppol2tp_seq_show+0xc20/0xc20 [ 26.998459] [] ? check_stack_object+0x68/0x140 [ 26.998469] [] ? security_socket_connect+0x89/0xb0 [ 26.998477] [] SYSC_connect+0x1b6/0x310 [ 26.998485] [] ? SYSC_bind+0x280/0x280 [ 26.998494] [] ? up_read+0x1a/0x40 [ 26.998503] [] ? __do_page_fault+0x3bd/0xd40 [ 26.998509] [] SyS_connect+0x24/0x30 [ 26.998515] [] ? SyS_accept+0x30/0x30 [ 26.998523] [] do_fast_syscall_32+0x2f5/0x870 [ 26.998529] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 26.998539] [] entry_SYSENTER_compat+0x90/0xa2 [ 26.998638] Code: f6 83 f8 00 00 00 02 75 35 e8 00 b0 de fd 48 8d 7b 10 be 10 00 00 00 e8 22 22 d1 fd 5b 5d c3 e8 ea af de fd 0f 0b e8 e3 af de fd <0f> 0b e8 1c e4 fb fd e9 65 ff ff ff e8 12 e4 fb fd eb c2 e8 cb [ 26.998645] RIP [] l2tp_tunnel_free+0xcd/0x110 [ 26.998647] RSP [ 26.999342] ---[ end trace 10ecbccff3e44da5 ]--- [ 26.999346] Kernel panic - not syncing: Fatal exception [ 27.288606] BUG: KASAN: use-after-free in l2tp_session_create+0x16ba/0x1770 [ 27.295678] Read of size 4 at addr ffff8801bd54f410 by task syzkaller699220/3755 [ 27.303179] [ 27.304786] CPU: 0 PID: 3755 Comm: syzkaller699220 Tainted: G D 4.9.83-g72766d7 #50 [ 27.313679] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.323007] ffff8801c1d2fa10 ffffffff81d95149 ffffea0006f55380 ffff8801bd54f410 [ 27.330998] 0000000000000000 ffff8801bd54f410 ffff8801c85d9400 ffff8801c1d2fa48 [ 27.338997] ffffffff8153e213 ffff8801bd54f410 0000000000000004 0000000000000000 [ 27.346992] Call Trace: [ 27.349554] [] dump_stack+0xc1/0x128 [ 27.354891] [] print_address_description+0x73/0x280 [ 27.361529] [] kasan_report+0x275/0x360 [ 27.367128] [] ? l2tp_session_create+0x16ba/0x1770 [ 27.373682] [] __asan_report_load4_noabort+0x14/0x20 [ 27.380411] [] l2tp_session_create+0x16ba/0x1770 [ 27.386787] [] ? l2tp_session_get+0x1ce/0x770 [ 27.392909] [] ? trace_hardirqs_on+0xd/0x10 [ 27.398855] [] pppol2tp_connect+0x10fe/0x18f0 [ 27.404973] [] ? pppol2tp_seq_show+0xc20/0xc20 [ 27.411180] [] ? check_stack_object+0x68/0x140 [ 27.417388] [] ? security_socket_connect+0x89/0xb0 [ 27.423942] [] SYSC_connect+0x1b6/0x310 [ 27.429541] [] ? SYSC_bind+0x280/0x280 [ 27.435053] [] ? memset+0x31/0x40 [ 27.440130] [] ? up_read+0x1a/0x40 [ 27.445295] [] ? __do_page_fault+0x3bd/0xd40 [ 27.451327] [] SyS_connect+0x24/0x30 [ 27.456667] [] ? SyS_accept+0x30/0x30 [ 27.462094] [] do_fast_syscall_32+0x2f5/0x870 [ 27.468210] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 27.474853] [] entry_SYSENTER_compat+0x90/0xa2 [ 27.481055] [ 27.482656] Allocated by task 3755: [ 27.486259] save_stack_trace+0x16/0x20 [ 27.490206] save_stack+0x43/0xd0 [ 27.493631] kasan_kmalloc+0xad/0xe0 [ 27.497315] __kmalloc+0x11d/0x310 [ 27.500826] l2tp_session_create+0x38/0x1770 [ 27.505208] pppol2tp_connect+0x10fe/0x18f0 [ 27.509503] SYSC_connect+0x1b6/0x310 [ 27.513275] SyS_connect+0x24/0x30 [ 27.516787] do_fast_syscall_32+0x2f5/0x870 [ 27.521082] entry_SYSENTER_compat+0x90/0xa2 [ 27.525469] [ 27.527082] Freed by task 3758: [ 27.530364] save_stack_trace+0x16/0x20 [ 27.534343] save_stack+0x43/0xd0 [ 27.537796] kasan_slab_free+0x72/0xc0 [ 27.541682] kfree+0x103/0x300 [ 27.544874] l2tp_session_free+0x166/0x200 [ 27.549111] pppol2tp_connect+0x108a/0x18f0 [ 27.553432] SYSC_connect+0x1b6/0x310 [ 27.557236] SyS_connect+0x24/0x30 [ 27.560775] do_fast_syscall_32+0x2f5/0x870 [ 27.565102] entry_SYSENTER_compat+0x90/0xa2 [ 27.569500] [ 27.571129] The buggy address belongs to the object at ffff8801bd54f400 [ 27.571129] which belongs to the cache kmalloc-512 of size 512 [ 27.583781] The buggy address is located 16 bytes inside of [ 27.583781] 512-byte region [ffff8801bd54f400, ffff8801bd54f600) [ 27.595561] The buggy address belongs to the page: [ 27.600489] page:ffffea0006f55380 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 27.610700] flags: 0x8000000000004080(slab|head) [ 27.615444] page dumped because: kasan: bad access detected [ 27.621141] [ 27.622753] Memory state around the buggy address: [ 27.627678] ffff8801bd54f300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.635037] ffff8801bd54f380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 27.642395] >ffff8801bd54f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.649748] ^ [ 27.653627] ffff8801bd54f480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.660977] ffff8801bd54f500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.668330] ================================================================== [ 27.676131] Dumping ftrace buffer: [ 27.679694] (ftrace buffer empty) [ 27.683388] Kernel Offset: disabled [ 27.686998] Rebooting in 86400 seconds..