================================================================== ------------[ cut here ]------------ kernel BUG at net/l2tp/l2tp_core.c:1405! invalid opcode: 0000 [#1] PREEMPT SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 3753 Comm: syzkaller699220 Not tainted 4.9.83-g72766d7 #50 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801b9d99800 task.stack: ffff8801c1df0000 RIP: 0010:[] [] l2tp_tunnel_free+0xcd/0x110 net/l2tp/l2tp_core.c:1405 RSP: 0018:ffff8801c1df7b18 EFLAGS: 00010293 RAX: ffff8801b9d99800 RBX: ffff8801c85d9400 RCX: ffffffff8358043d RDX: 0000000000000000 RSI: ffff8801c85d9580 RDI: ffff8801c85d9580 RBP: ffff8801c1df7b20 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c85d9400 R13: ffff8801bd54f408 R14: ffff8801d6293980 R15: 1ffff100383bef75 FS: 0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f76ffb40 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 00000000207e8ff8 CR3: 00000001bf9de000 CR4: 0000000000160670 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffff8801bd54f400 ffff8801c1df7b50 ffffffff8358575d ffff8801bd54f400 ffff8801d70eb300 00000000ffffffef ffff8801c85d9400 ffff8801c1df7d10 ffffffff8358deea ffff8801c1df7ca8 00000112c4b9cbd0 ffff880100000002 Call Trace: [] l2tp_tunnel_dec_refcount_1 net/l2tp/l2tp_core.c:141 [inline] [] l2tp_session_free+0x18d/0x200 net/l2tp/l2tp_core.c:1763 [] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:297 [inline] [] pppol2tp_connect+0x108a/0x18f0 net/l2tp/l2tp_ppp.c:783 [] SYSC_connect+0x1b6/0x310 net/socket.c:1562 [] SyS_connect+0x24/0x30 net/socket.c:1543 [] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline] [] do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387 [] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 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 RIP [] l2tp_tunnel_free+0xcd/0x110 net/l2tp/l2tp_core.c:1405 RSP ---[ end trace 10ecbccff3e44da5 ]--- Kernel panic - not syncing: Fatal exception BUG: KASAN: use-after-free in l2tp_session_create+0x16ba/0x1770 net/l2tp/l2tp_core.c:1910 Read of size 4 at addr ffff8801bd54f410 by task syzkaller699220/3755 CPU: 0 PID: 3755 Comm: syzkaller699220 Tainted: G D 4.9.83-g72766d7 #50 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801c1d2fa10 ffffffff81d95149 ffffea0006f55380 ffff8801bd54f410 0000000000000000 ffff8801bd54f410 ffff8801c85d9400 ffff8801c1d2fa48 ffffffff8153e213 ffff8801bd54f410 0000000000000004 0000000000000000 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] print_address_description+0x73/0x280 mm/kasan/report.c:252 [] kasan_report_error mm/kasan/report.c:351 [inline] [] kasan_report+0x275/0x360 mm/kasan/report.c:408 [] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428 [] l2tp_session_create+0x16ba/0x1770 net/l2tp/l2tp_core.c:1910 [] pppol2tp_connect+0x10fe/0x18f0 net/l2tp/l2tp_ppp.c:711 [] SYSC_connect+0x1b6/0x310 net/socket.c:1562 [] SyS_connect+0x24/0x30 net/socket.c:1543 [] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline] [] do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387 [] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 Allocated by task 3755: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 save_stack+0x43/0xd0 mm/kasan/kasan.c:505 set_track mm/kasan/kasan.c:517 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:609 __kmalloc+0x11d/0x310 mm/slub.c:3741 kmalloc include/linux/slab.h:495 [inline] kzalloc include/linux/slab.h:636 [inline] l2tp_session_create+0x38/0x1770 net/l2tp/l2tp_core.c:1839 pppol2tp_connect+0x10fe/0x18f0 net/l2tp/l2tp_ppp.c:711 SYSC_connect+0x1b6/0x310 net/socket.c:1562 SyS_connect+0x24/0x30 net/socket.c:1543 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline] do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 Freed by task 3758: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 save_stack+0x43/0xd0 mm/kasan/kasan.c:505 set_track mm/kasan/kasan.c:517 [inline] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582 slab_free_hook mm/slub.c:1355 [inline] slab_free_freelist_hook mm/slub.c:1377 [inline] slab_free mm/slub.c:2958 [inline] kfree+0x103/0x300 mm/slub.c:3878 l2tp_session_free+0x166/0x200 net/l2tp/l2tp_core.c:1766 l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:297 [inline] pppol2tp_connect+0x108a/0x18f0 net/l2tp/l2tp_ppp.c:783 SYSC_connect+0x1b6/0x310 net/socket.c:1562 SyS_connect+0x24/0x30 net/socket.c:1543 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline] do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 The buggy address belongs to the object at ffff8801bd54f400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 16 bytes inside of 512-byte region [ffff8801bd54f400, ffff8801bd54f600) The buggy address belongs to the page: page:ffffea0006f55380 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 flags: 0x8000000000004080(slab|head) page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801bd54f300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801bd54f380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8801bd54f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801bd54f480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801bd54f500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: disabled Rebooting in 86400 seconds..