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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 ffff8801bd8c5658 by task syz-executor3/9413

CPU: 0 PID: 9413 Comm: syz-executor3 Not tainted 4.9.82-g7ec482b #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801b0537ac0 ffffffff81d94fc9 ffffea0006f63000 ffff8801bd8c5658
 0000000000000000 ffff8801bd8c5658 1ffff100360a6f75 ffff8801b0537af8
 ffffffff8153e213 ffff8801bd8c5658 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81d94fc9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94fc9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8153e213>] print_address_description+0x73/0x280 mm/kasan/report.c:252
 [<ffffffff8153e735>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8153e735>] kasan_report+0x275/0x360 mm/kasan/report.c:408
 [<ffffffff8153e894>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff8358e709>] __read_once_size include/linux/compiler.h:243 [inline]
 [<ffffffff8358e709>] sk_dst_get include/net/sock.h:1695 [inline]
 [<ffffffff8358e709>] pppol2tp_connect+0x18a9/0x18f0 net/l2tp/l2tp_ppp.c:739
 [<ffffffff82ed96e6>] SYSC_connect+0x1b6/0x310 net/socket.c:1562
 [<ffffffff82edbf64>] SyS_connect+0x24/0x30 net/socket.c:1543
 [<ffffffff81006f97>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006f97>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff838b6574>] entry_SYSENTER_compat+0x74/0x83 arch/x86/entry/entry_64_compat.S:127

Allocated by task 9367:
 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
 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 entry_SYSENTER_compat+0x74/0x83 arch/x86/entry/entry_64_compat.S:127

Freed by task 9391:
 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 ffff8801bd8c5480
 which belongs to the cache UDPv6 of size 1496
The buggy address is located 472 bytes inside of
 1496-byte region [ffff8801bd8c5480, ffff8801bd8c5a58)
The buggy address belongs to the page:
page:ffffea0006f63000 count:1 mapcount:0 mapping:          (null) index:0xffff8801bd8c7500 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bd8c5500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bd8c5580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801bd8c5600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff8801bd8c5680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bd8c5700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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