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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:1768 [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 ffff8801ac41bb28 by task syz-executor7/17950

CPU: 1 PID: 17950 Comm: syz-executor7 Not tainted 4.16.0-rc6+ #279
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:1768 [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: 0033:0x454239
RSP: 002b:00007ff9a0b2cc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007ff9a0b2d6d4 RCX: 0000000000454239
RDX: 000000000000002e RSI: 0000000020e92000 RDI: 0000000000000016
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000005c R14: 00000000006f1940 R15: 0000000000000000

Allocated by task 17950:
 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:3541
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1468
 sk_alloc+0x105/0x1440 net/core/sock.c:1528
 inet_create+0x47c/0xf50 net/ipv4/af_inet.c:320
 __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 24530:
 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:3485 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3743
 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:1660 [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 ffff8801ac41b900
 which belongs to the cache UDP of size 1536
The buggy address is located 552 bytes inside of
 1536-byte region [ffff8801ac41b900, ffff8801ac41bf00)
The buggy address belongs to the page:
page:ffffea0006b10680 count:1 mapcount:0 mapping:ffff8801ac41a580 index:0xffff8801ac41b280 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801ac41a580 ffff8801ac41b280 0000000100000003
raw: ffffea0006c30a20 ffffea000752c2a0 ffff8801d6be7640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ac41ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ac41ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801ac41bb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801ac41bb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ac41bc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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