================================================================== BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:917 Read of size 4 at addr ffff8801d4ff1180 by task syz-executor1/22172 CPU: 0 PID: 22172 Comm: syz-executor1 Not tainted 4.9.124-g09eb2ba #83 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801cb187ca8 ffffffff81eb95e9 ffffea000753fc00 ffff8801d4ff1180 0000000000000000 ffff8801d4ff1180 0000000000000000 ffff8801cb187ce0 ffffffff8156c35e ffff8801d4ff1180 0000000000000004 0000000000000000 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] print_address_description+0x6c/0x234 mm/kasan/report.c:256 [] kasan_report_error mm/kasan/report.c:355 [inline] [] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412 [] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 [] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:917 [] pppol2tp_release+0x1fb/0x2e0 net/l2tp/l2tp_ppp.c:492 [] __sock_release+0xd7/0x260 net/socket.c:605 [] sock_close+0x19/0x20 net/socket.c:1059 [] __fput+0x263/0x700 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x10c/0x180 kernel/task_work.c:116 [] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161 [] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline] [] syscall_return_slowpath arch/x86/entry/common.c:260 [inline] [] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Allocated by task 22180: 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+0xc7/0xe0 mm/kasan/kasan.c:609 __kmalloc+0x11d/0x300 mm/slub.c:3741 kmalloc include/linux/slab.h:495 [inline] kzalloc include/linux/slab.h:636 [inline] l2tp_session_create+0x38/0x16f0 net/l2tp/l2tp_core.c:1843 pppol2tp_connect+0x10d7/0x18f0 net/l2tp/l2tp_ppp.c:718 SYSC_connect+0x1b8/0x300 net/socket.c:1575 SyS_connect+0x24/0x30 net/socket.c:1556 do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282 entry_SYSCALL_64_after_swapgs+0x5d/0xdb Freed by task 22180: 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+0xfb/0x310 mm/slub.c:3878 l2tp_session_free+0x166/0x200 net/l2tp/l2tp_core.c:1770 l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:297 [inline] l2tp_tunnel_closeall+0x284/0x350 net/l2tp/l2tp_core.c:1373 l2tp_udp_encap_destroy+0x87/0xe0 net/l2tp/l2tp_core.c:1394 udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1336 sk_common_release+0x6d/0x300 net/core/sock.c:2727 udp_lib_close+0x15/0x20 include/net/udp.h:203 inet_release+0xff/0x1d0 net/ipv4/af_inet.c:434 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:440 __sock_release+0xd7/0x260 net/socket.c:605 sock_close+0x19/0x20 net/socket.c:1059 __fput+0x263/0x700 fs/file_table.c:208 ____fput+0x15/0x20 fs/file_table.c:244 task_work_run+0x10c/0x180 kernel/task_work.c:116 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161 prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline] syscall_return_slowpath arch/x86/entry/common.c:260 [inline] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_swapgs+0x5d/0xdb The buggy address belongs to the object at ffff8801d4ff1180 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8801d4ff1180, ffff8801d4ff1380) The buggy address belongs to the page: page:ffffea000753fc00 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: ffff8801d4ff1080: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc ffff8801d4ff1100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8801d4ff1180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801d4ff1200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801d4ff1280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== IPVS: Creating netns size=2536 id=56