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BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:188 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1772 [inline]
BUG: KASAN: use-after-free in pppol2tp_session_init net/l2tp/l2tp_ppp.c:587 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x1a98/0x1dd0 net/l2tp/l2tp_ppp.c:747
Read of size 8 at addr ffff8801d691e368 by task syz-executor2/5453

CPU: 0 PID: 5453 Comm: syz-executor2 Not tainted 4.16.0-rc7+ #291
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 __read_once_size include/linux/compiler.h:188 [inline]
 sk_dst_get include/net/sock.h:1772 [inline]
 pppol2tp_session_init net/l2tp/l2tp_ppp.c:587 [inline]
 pppol2tp_connect+0x1a98/0x1dd0 net/l2tp/l2tp_ppp.c:747
 SYSC_connect+0x213/0x4a0 net/socket.c:1640
 SyS_connect+0x24/0x30 net/socket.c:1621
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x455269
RSP: 002b:00007ff47180ac68 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007ff47180b6d4 RCX: 0000000000455269
RDX: 000000000000002e RSI: 00000000205fafd2 RDI: 0000000000000004
RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000005c R14: 00000000006f2940 R15: 0000000000000001

Allocated by task 5449:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3542
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1468
 sk_alloc+0x105/0x1440 net/core/sock.c:1528
 inet6_create+0x44d/0x10f0 net/ipv6/af_inet6.c:183
 __sock_create+0x4d4/0x850 net/socket.c:1285
 sock_create net/socket.c:1325 [inline]
 SYSC_socket net/socket.c:1355 [inline]
 SyS_socket+0xeb/0x1d0 net/socket.c:1335
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 7135:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3486 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3744
 sk_prot_free net/core/sock.c:1509 [inline]
 __sk_destruct+0x628/0x920 net/core/sock.c:1593
 sk_destruct+0x47/0x80 net/core/sock.c:1601
 __sk_free+0xf1/0x2b0 net/core/sock.c:1612
 sk_free+0x2a/0x40 net/core/sock.c:1623
 sock_put include/net/sock.h:1664 [inline]
 l2tp_tunnel_free net/l2tp/l2tp_core.c:160 [inline]
 l2tp_tunnel_dec_refcount net/l2tp/l2tp_core.h:264 [inline]
 l2tp_tunnel_del_work+0x474/0x6a0 net/l2tp/l2tp_core.c:1307
 process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
 worker_thread+0x223/0x1990 kernel/workqueue.c:2247
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

The buggy address belongs to the object at ffff8801d691e140
 which belongs to the cache UDPv6 of size 1728
The buggy address is located 552 bytes inside of
 1728-byte region [ffff8801d691e140, ffff8801d691e800)
The buggy address belongs to the page:
page:ffffea00075a4780 count:1 mapcount:0 mapping:ffff8801d691e140 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d691e140 0000000000000000 0000000100000002
raw: ffffea00073ed6a0 ffffea00076bc2e0 ffff8801ce551080 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d691e200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d691e280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d691e300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801d691e380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d691e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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