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 ffff8801cd83833c by task syz-executor5/4595

CPU: 0 PID: 4595 Comm: syz-executor5 Not tainted 4.17.0+ #116
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
 compat_ip_getsockopt+0x256/0x2f0 net/ipv4/ip_sockglue.c:1600
 inet_csk_compat_getsockopt+0x97/0x120 net/ipv4/inet_connection_sock.c:1023
 compat_tcp_getsockopt+0x49/0x80 net/ipv4/tcp.c:3543
 compat_sock_common_getsockopt+0xb4/0x150 net/core/sock.c:3023
 __compat_sys_getsockopt+0x1ae/0x880 net/compat.c:532
 __do_compat_sys_socketcall net/compat.c:916 [inline]
 __se_compat_sys_socketcall net/compat.c:844 [inline]
 __ia32_compat_sys_socketcall+0xcd1/0x1070 net/compat.c:844
 do_syscall_32_irqs_on arch/x86/entry/common.c:323 [inline]
 do_fast_syscall_32+0x345/0xf9b arch/x86/entry/common.c:394
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f35cb9
Code: 55 08 8b 88 64 cd ff ff 8b 98 68 cd ff ff 89 c8 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 1c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 
RSP: 002b:000000000845e340 EFLAGS: 00000206 ORIG_RAX: 0000000000000066
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 000000000845e35c
RDX: 000000000845e3b4 RSI: 000000000845e3b4 RDI: 000000000845e408
RBP: 000000000811fe18 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 2224:
 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 1619:
 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 ffff8801cd8382c0
 which belongs to the cache filp of size 456
The buggy address is located 124 bytes inside of
 456-byte region [ffff8801cd8382c0, ffff8801cd838488)
The buggy address belongs to the page:
page:ffffea0007360e00 count:1 mapcount:0 mapping:ffff8801da986940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006c07088 ffffea0007627a88 ffff8801da986940
raw: 0000000000000000 ffff8801cd838040 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cd838200: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801cd838280: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8801cd838300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8801cd838380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cd838400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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