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BUG: KASAN: use-after-free in inet_shutdown+0x2d4/0x350 net/ipv4/af_inet.c:824
Read of size 4 at addr ffff8801d5f36a80 by task syz-executor7/5048

CPU: 0 PID: 5048 Comm: syz-executor7 Not tainted 4.9.82-gcdfc8df #45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c6b27b78 ffffffff81d94fc9 ffffea000757cd00 ffff8801d5f36a80
 0000000000000000 ffff8801d5f36a80 ffff8801c6b971d8 ffff8801c6b27bb0
 ffffffff8153e213 ffff8801d5f36a80 0000000000000004 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
 [<ffffffff8153e874>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff832e9e74>] inet_shutdown+0x2d4/0x350 net/ipv4/af_inet.c:824
 [<ffffffff8358b910>] pppol2tp_session_close+0xa0/0xe0 net/l2tp/l2tp_ppp.c:441
 [<ffffffff8358630f>] l2tp_tunnel_closeall+0x21f/0x3a0 net/l2tp/l2tp_core.c:1368
 [<ffffffff83586f17>] l2tp_udp_encap_destroy+0x87/0xe0 net/l2tp/l2tp_core.c:1394
 [<ffffffff8348cc41>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1336
 [<ffffffff82eec5cb>] sk_common_release+0x6b/0x2f0 net/core/sock.c:2727
 [<ffffffff8348bbf5>] udp_lib_close+0x15/0x20 include/net/udp.h:203
 [<ffffffff832e9fea>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:434
 [<ffffffff83410c60>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:440
 [<ffffffff82ed589d>] sock_release+0x8d/0x1e0 net/socket.c:599
 [<ffffffff82ed5a06>] sock_close+0x16/0x20 net/socket.c:1046
 [<ffffffff8157580c>] __fput+0x28c/0x6e0 fs/file_table.c:208
 [<ffffffff81575ce5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff81195855>] task_work_run+0x115/0x190 kernel/task_work.c:116
 [<ffffffff81003a4c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff81003a4c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 [<ffffffff81007263>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff81007263>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff81007263>] do_syscall_32_irqs_on arch/x86/entry/common.c:331 [inline]
 [<ffffffff81007263>] do_fast_syscall_32+0x5c3/0x870 arch/x86/entry/common.c:387
 [<ffffffff838b6574>] entry_SYSENTER_compat+0x74/0x83 arch/x86/entry/entry_64_compat.S:127

Allocated by task 5074:
 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
 sock_alloc_inode+0x1d/0x250 net/socket.c:250
 alloc_inode+0x65/0x180 fs/inode.c:207
 new_inode_pseudo+0x17/0xe0 fs/inode.c:890
 sock_alloc+0x41/0x270 net/socket.c:567
 __sock_create+0xa5/0x640 net/socket.c:1146
 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 5074:
 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
 sock_destroy_inode+0x56/0x70 net/socket.c:280
 destroy_inode+0xc3/0x120 fs/inode.c:264
 evict+0x329/0x4f0 fs/inode.c:570
 iput_final fs/inode.c:1516 [inline]
 iput+0x47b/0x900 fs/inode.c:1543
 dentry_unlink_inode+0x470/0x570 fs/dcache.c:370
 __dentry_kill+0x25b/0x480 fs/dcache.c:565
 dentry_kill fs/dcache.c:606 [inline]
 dput.part.23+0x680/0x7b0 fs/dcache.c:818
 dput+0x1f/0x30 fs/dcache.c:780
 __fput+0x46a/0x6e0 fs/file_table.c:226
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x115/0x190 kernel/task_work.c:116
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 do_syscall_32_irqs_on arch/x86/entry/common.c:331 [inline]
 do_fast_syscall_32+0x5c3/0x870 arch/x86/entry/common.c:387
 entry_SYSENTER_compat+0x74/0x83 arch/x86/entry/entry_64_compat.S:127

The buggy address belongs to the object at ffff8801d5f36a80
 which belongs to the cache sock_inode_cache of size 944
The buggy address is located 0 bytes inside of
 944-byte region [ffff8801d5f36a80, ffff8801d5f36e30)
The buggy address belongs to the page:
page:ffffea000757cd00 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:
 ffff8801d5f36980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff8801d5f36a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d5f36a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801d5f36b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d5f36b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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