INIT: Entering runlevel: 2 [info] Using makefile-style concurrent boot in runlevel 2. [....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?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 '10.128.0.51' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.016108] ================================================================== [ 27.023479] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 27.030719] Read of size 4 at addr ffff8801b66a8f00 by task syzkaller533403/3780 [ 27.038216] [ 27.039814] CPU: 0 PID: 3780 Comm: syzkaller533403 Not tainted 4.9.92-g7cd9561 #1 [ 27.047408] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.056728] ffff8801b6787cb0 ffffffff81d9c489 ffffea0006d9aa00 ffff8801b66a8f00 [ 27.064690] 0000000000000000 ffff8801b66a8f00 ffffffff82ef0be0 ffff8801b6787ce8 [ 27.072647] ffffffff8156556b ffff8801b66a8f00 0000000000000004 0000000000000000 [ 27.080606] Call Trace: [ 27.083160] [] dump_stack+0xc1/0x128 [ 27.088492] [] ? sock_release+0x1c0/0x1c0 [ 27.094259] [] print_address_description+0x6c/0x234 [ 27.100891] [] ? sock_release+0x1c0/0x1c0 [ 27.106655] [] kasan_report.cold.6+0xac/0x2f5 [ 27.112775] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 27.119495] [] __asan_report_load4_noabort+0x14/0x20 [ 27.126217] [] l2tp_session_queue_purge+0xf4/0x100 [ 27.132762] [] ? sock_release+0x1c0/0x1c0 [ 27.138528] [] pppol2tp_release+0x1fb/0x2e0 [ 27.144467] [] sock_release+0x96/0x1c0 [ 27.149969] [] sock_close+0x16/0x20 [ 27.155214] [] __fput+0x263/0x700 [ 27.160285] [] ____fput+0x15/0x20 [ 27.165354] [] task_work_run+0x10c/0x180 [ 27.171033] [] exit_to_usermode_loop+0xfc/0x120 [ 27.177318] [] do_syscall_64+0x364/0x490 [ 27.182995] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.189883] [ 27.191477] Allocated by task 3779: [ 27.195072] save_stack_trace+0x16/0x20 [ 27.199013] save_stack+0x43/0xd0 [ 27.202430] kasan_kmalloc+0xc7/0xe0 [ 27.206111] __kmalloc+0x11d/0x300 [ 27.209618] l2tp_session_create+0x38/0x1760 [ 27.213990] pppol2tp_connect+0x10c5/0x18e0 [ 27.218281] SYSC_connect+0x1b8/0x300 [ 27.222045] SyS_connect+0x24/0x30 [ 27.225550] do_syscall_64+0x1a6/0x490 [ 27.229404] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.234469] [ 27.236071] Freed by task 3779: [ 27.239320] save_stack_trace+0x16/0x20 [ 27.243259] save_stack+0x43/0xd0 [ 27.246678] kasan_slab_free+0x72/0xc0 [ 27.250533] kfree+0xfb/0x310 [ 27.253602] l2tp_session_free+0x166/0x200 [ 27.257803] l2tp_tunnel_closeall+0x284/0x350 [ 27.262264] l2tp_udp_encap_destroy+0x87/0xe0 [ 27.266725] udpv6_destroy_sock+0xb1/0xd0 [ 27.270841] sk_common_release+0x6d/0x300 [ 27.274953] udp_lib_close+0x15/0x20 [ 27.278633] inet_release+0xff/0x1d0 [ 27.282314] inet6_release+0x50/0x70 [ 27.285992] sock_release+0x96/0x1c0 [ 27.289678] sock_close+0x16/0x20 [ 27.293096] __fput+0x263/0x700 [ 27.296341] ____fput+0x15/0x20 [ 27.299588] task_work_run+0x10c/0x180 [ 27.303440] exit_to_usermode_loop+0xfc/0x120 [ 27.307911] do_syscall_64+0x364/0x490 [ 27.311770] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.316834] [ 27.318428] The buggy address belongs to the object at ffff8801b66a8f00 [ 27.318428] which belongs to the cache kmalloc-512 of size 512 [ 27.331052] The buggy address is located 0 bytes inside of [ 27.331052] 512-byte region [ffff8801b66a8f00, ffff8801b66a9100) [ 27.342715] The buggy address belongs to the page: [ 27.347611] page:ffffea0006d9aa00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 27.357768] flags: 0x8000000000004080(slab|head) [ 27.362485] page dumped because: kasan: bad access detected [ 27.368156] [ 27.369749] Memory state around the buggy address: [ 27.374646] ffff8801b66a8e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.381974] ffff8801b66a8e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 27.389299] >ffff8801b66a8f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.396621] ^ [ 27.399951] ffff8801b66a8f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.407278] ffff8801b66a9000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 27.414601] ================================================================== [ 27.421925] Disabling lock debugging due to kernel taint [ 27.427462] Kernel panic - not syncing: panic_on_warn set ... [ 27.427462] [ 27.434806] CPU: 0 PID: 3780 Comm: syzkaller533403 Tainted: G B 4.9.92-g7cd9561 #1 [ 27.443608] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.452931] ffff8801b6787c10 ffffffff81d9c489 ffffffff841a85f1 00000000ffffffff [ 27.460889] 0000000000000000 0000000000000000 ffffffff82ef0be0 ffff8801b6787cd0 [ 27.468847] ffffffff8141fa55 0000000041b58ab3 ffffffff8419bd28 ffffffff8141f896 [ 27.476810] Call Trace: [ 27.479367] [] dump_stack+0xc1/0x128 [ 27.484698] [] ? sock_release+0x1c0/0x1c0 [ 27.490465] [] panic+0x1bf/0x3bc [ 27.495446] [] ? add_taint.cold.6+0x16/0x16 [ 27.501386] [] ? ___preempt_schedule+0x16/0x18 [ 27.507587] [] kasan_end_report+0x47/0x4f [ 27.513352] [] kasan_report.cold.6+0xc9/0x2f5 [ 27.519464] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 27.526181] [] __asan_report_load4_noabort+0x14/0x20 [ 27.532902] [] l2tp_session_queue_purge+0xf4/0x100 [ 27.539450] [] ? sock_release+0x1c0/0x1c0 [ 27.545213] [] pppol2tp_release+0x1fb/0x2e0 [ 27.551151] [] sock_release+0x96/0x1c0 [ 27.556657] [] sock_close+0x16/0x20 [ 27.561901] [] __fput+0x263/0x700 [ 27.566974] [] ____fput+0x15/0x20 [ 27.572044] [] task_work_run+0x10c/0x180 [ 27.577721] [] exit_to_usermode_loop+0xfc/0x120 [ 27.584005] [] do_syscall_64+0x364/0x490 [ 27.589683] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.597057] Dumping ftrace buffer: [ 27.600566] (ftrace buffer empty) [ 27.604243] Kernel Offset: disabled [ 27.607835] Rebooting in 86400 seconds..