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BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:243 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1695 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x18a9/0x18f0 net/l2tp/l2tp_ppp.c:739
Read of size 8 at addr ffff8801ae88dcd8 by task syz-executor3/8813

CPU: 0 PID: 8813 Comm: syz-executor3 Not tainted 4.9.78-g7be1985 #24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801bc1a7b28 ffffffff81d94409 ffffea0006ba2200 ffff8801ae88dcd8
 0000000000000000 ffff8801ae88dcd8 1ffff10037834f82 ffff8801bc1a7b60
 ffffffff8153dc73 ffff8801ae88dcd8 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81d94409>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94409>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8153dc73>] print_address_description+0x73/0x280 mm/kasan/report.c:252
 [<ffffffff8153e195>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8153e195>] kasan_report+0x275/0x360 mm/kasan/report.c:408
 [<ffffffff8153e2f4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff8358c4b9>] __read_once_size include/linux/compiler.h:243 [inline]
 [<ffffffff8358c4b9>] sk_dst_get include/net/sock.h:1695 [inline]
 [<ffffffff8358c4b9>] pppol2tp_connect+0x18a9/0x18f0 net/l2tp/l2tp_ppp.c:739
 [<ffffffff82ed86e6>] SYSC_connect+0x1b6/0x310 net/socket.c:1562
 [<ffffffff82edaf44>] SyS_connect+0x24/0x30 net/socket.c:1543
 [<ffffffff838b2c6e>] entry_SYSCALL_64_fastpath+0x29/0xe8

Allocated by task 7515:
 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
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:547
 slab_post_alloc_hook mm/slab.h:417 [inline]
 slab_alloc_node mm/slub.c:2715 [inline]
 slab_alloc mm/slub.c:2723 [inline]
 kmem_cache_alloc+0xba/0x290 mm/slub.c:2728
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1332
 sk_alloc+0x3a/0x3a0 net/core/sock.c:1394
 inet6_create+0x2c8/0xde0 net/ipv6/af_inet6.c:198
 __sock_create+0x3ab/0x640 net/socket.c:1182
 sock_create net/socket.c:1222 [inline]
 SYSC_socket net/socket.c:1252 [inline]
 SyS_socket+0xf0/0x1b0 net/socket.c:1232
 entry_SYSCALL_64_fastpath+0x29/0xe8

Freed by task 7564:
 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]
 kmem_cache_free+0xc7/0x300 mm/slub.c:2980
 sk_prot_free net/core/sock.c:1375 [inline]
 __sk_destruct+0x3c9/0x570 net/core/sock.c:1455
 __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 rcu_process_callbacks+0x898/0x1300 kernel/rcu/tree.c:3037
 __do_softirq+0x206/0x951 kernel/softirq.c:284

The buggy address belongs to the object at ffff8801ae88db00
 which belongs to the cache UDPv6 of size 1496
The buggy address is located 472 bytes inside of
 1496-byte region [ffff8801ae88db00, ffff8801ae88e0d8)
The buggy address belongs to the page:
page:ffffea0006ba2200 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:
 ffff8801ae88db80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ae88dc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801ae88dc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff8801ae88dd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ae88dd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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