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BUG: KASAN: use-after-free in inet_shutdown+0x2dc/0x360 net/ipv4/af_inet.c:824
Read of size 4 at addr ffff8801cbe7f740 by task syz-executor1/9106

CPU: 1 PID: 9106 Comm: syz-executor1 Not tainted 4.9.123-g7fa8c15 #80
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801a0e1fb88 ffffffff81eb9689 ffffea00072f9f00 ffff8801cbe7f740
 0000000000000000 ffff8801cbe7f740 ffff8801bc698058 ffff8801a0e1fbc0
 ffffffff8156c3fe ffff8801cbe7f740 0000000000000004 0000000000000000
Call Trace:
 [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb9689>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8156c3fe>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff8156c808>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff8156c808>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153fb74>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 [<ffffffff8342904c>] inet_shutdown+0x2dc/0x360 net/ipv4/af_inet.c:824
 [<ffffffff836cbac0>] pppol2tp_session_close+0xa0/0xe0 net/l2tp/l2tp_ppp.c:441
 [<ffffffff836c52f1>] l2tp_tunnel_closeall+0x231/0x350 net/l2tp/l2tp_core.c:1368
 [<ffffffff836c5e97>] l2tp_udp_encap_destroy+0x87/0xe0 net/l2tp/l2tp_core.c:1394
 [<ffffffff835cc331>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1336
 [<ffffffff83031a5d>] sk_common_release+0x6d/0x300 net/core/sock.c:2727
 [<ffffffff835cafe5>] udp_lib_close+0x15/0x20 include/net/udp.h:203
 [<ffffffff834291cf>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:434
 [<ffffffff83550ff0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:440
 [<ffffffff83018357>] __sock_release+0xd7/0x260 net/socket.c:605
 [<ffffffff830184f9>] sock_close+0x19/0x20 net/socket.c:1059
 [<ffffffff8157cb13>] __fput+0x263/0x700 fs/file_table.c:208
 [<ffffffff8157d035>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8119a66c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8100559c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff83a01d93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 9133:
 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
 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+0xbe/0x290 mm/slub.c:2728
 sock_alloc_inode+0x1d/0x260 net/socket.c:251
 alloc_inode+0x63/0x180 fs/inode.c:207
 new_inode_pseudo+0x17/0xe0 fs/inode.c:890
 sock_alloc+0x41/0x280 net/socket.c:571
 __sock_create+0x8d/0x5f0 net/socket.c:1159
 sock_create net/socket.c:1235 [inline]
 SYSC_socket net/socket.c:1265 [inline]
 SyS_socket+0xf0/0x1b0 net/socket.c:1245
 do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 9133:
 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+0xbe/0x310 mm/slub.c:2980
 sock_destroy_inode+0x56/0x70 net/socket.c:281
 destroy_inode+0xc5/0x120 fs/inode.c:264
 evict+0x32b/0x4f0 fs/inode.c:570
 iput_final fs/inode.c:1516 [inline]
 iput+0x371/0x900 fs/inode.c:1543
 dentry_unlink_inode+0x277/0x330 fs/dcache.c:367
 __dentry_kill+0x280/0x4c0 fs/dcache.c:569
 dentry_kill fs/dcache.c:610 [inline]
 dput.part.29+0x5cf/0x7b0 fs/dcache.c:827
 dput+0x1f/0x30 fs/dcache.c:789
 __fput+0x42f/0x700 fs/file_table.c:226
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x10c/0x180 kernel/task_work.c:116
 get_signal+0x1133/0x1450 kernel/signal.c:2151
 do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807
 exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:157
 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 ffff8801cbe7f740
 which belongs to the cache sock_inode_cache of size 960
The buggy address is located 0 bytes inside of
 960-byte region [ffff8801cbe7f740, ffff8801cbe7fb00)
The buggy address belongs to the page:
page:ffffea00072f9f00 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:
 ffff8801cbe7f600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801cbe7f680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff8801cbe7f700: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                           ^
 ffff8801cbe7f780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cbe7f800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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