bpfilter: read fail -512
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BUG: KASAN: use-after-free in __kernel_write+0x301/0x380 fs/read_write.c:498
Read of size 4 at addr ffff8801cdee887c by task syz-executor7/4574

CPU: 1 PID: 4574 Comm: syz-executor7 Not tainted 4.17.0+ #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 __kernel_write+0x301/0x380 fs/read_write.c:498
 __bpfilter_process_sockopt+0x1d8/0x35b net/bpfilter/bpfilter_kern.c:66
 bpfilter_mbox_request+0x4d/0xb0 net/ipv4/bpfilter/sockopt.c:25
 bpfilter_ip_get_sockopt+0x6b/0x90 net/ipv4/bpfilter/sockopt.c:42
 ip_getsockopt+0x238/0x2a0 net/ipv4/ip_sockglue.c:1563
 tcp_getsockopt+0x93/0xe0 net/ipv4/tcp.c:3532
 sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:3012
 __sys_getsockopt+0x1a5/0x370 net/socket.c:1972
 __do_sys_getsockopt net/socket.c:1983 [inline]
 __se_sys_getsockopt net/socket.c:1980 [inline]
 __x64_sys_getsockopt+0xbe/0x150 net/socket.c:1980
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4584ea
Code: b8 34 01 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 1d 8f fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 fa 8e fb ff c3 66 0f 1f 84 00 00 00 00 00 
RSP: 002b:0000000000a3e328 EFLAGS: 00000212 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000a3e350 RCX: 00000000004584ea
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000013
RBP: 0000000000705f20 R08: 0000000000a3e34c R09: 0000000000004000
R10: 0000000000a3e450 R11: 0000000000000212 R12: 0000000000000013
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000704ae0

Allocated by task 2222:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
 kmem_cache_zalloc include/linux/slab.h:696 [inline]
 get_empty_filp+0x125/0x520 fs/file_table.c:122
 alloc_file+0x24/0x3e0 fs/file_table.c:163
 create_pipe_files+0x4db/0x940 fs/pipe.c:763
 umh_pipe_setup+0xac/0x430 kernel/umh.c:431
 call_usermodehelper_exec_async+0x3c0/0x9e0 kernel/umh.c:93
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Freed by task 14520:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
 file_free_rcu+0x6f/0x90 fs/file_table.c:49
 __rcu_reclaim kernel/rcu/rcu.h:178 [inline]
 rcu_do_batch kernel/rcu/tree.c:2558 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2818 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2785 [inline]
 rcu_process_callbacks+0xe9d/0x1760 kernel/rcu/tree.c:2802
 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:284

The buggy address belongs to the object at ffff8801cdee8800
 which belongs to the cache filp of size 456
The buggy address is located 124 bytes inside of
 456-byte region [ffff8801cdee8800, ffff8801cdee89c8)
The buggy address belongs to the page:
page:ffffea000737ba00 count:1 mapcount:0 mapping:ffff8801cdee8080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cdee8080 0000000000000000 0000000100000006
raw: ffffea000760b6a0 ffffea000763bfe0 ffff8801da986940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cdee8700: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
 ffff8801cdee8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801cdee8800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8801cdee8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cdee8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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