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SubjectKASAN: use-after-free Read in selinux_netlbl_socket_setsockopt

syzbot found the following crash on:

HEAD commit: 62967898789d Merge git://
git tree: upstream
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:

8021q: adding VLAN 0 to HW filter on device team0
BUG: KASAN: use-after-free in selinux_netlbl_socket_setsockopt+0x49b/0x510
Read of size 8 at addr ffff8880a63cf078 by task syz-executor3/18477

CPU: 1 PID: 18477 Comm: syz-executor3 Not tainted 5.0.0-rc4+ #51
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+0x1db/0x2d0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
selinux_socket_setsockopt+0x67/0x90 security/selinux/hooks.c:4693
security_socket_setsockopt+0x7d/0xc0 security/security.c:1467
__sys_setsockopt+0xe4/0x3a0 net/socket.c:1892
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
RIP: 0033:0x458089
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb988b9cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000458089
RDX: 0000000000000078 RSI: 0000000000000084 RDI: 000000000000000a
RBP: 000000000073c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb988b9d6d4
R13: 00000000004cc9e8 R14: 00000000004da6a8 R15: 00000000ffffffff

Allocated by task 18471:
save_stack+0x45/0xd0 mm/kasan/common.c:73
set_track mm/kasan/common.c:85 [inline]
__kasan_kmalloc mm/kasan/common.c:496 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:504
__do_kmalloc mm/slab.c:3711 [inline]
__kmalloc+0x15c/0x740 mm/slab.c:3720
kmalloc include/linux/slab.h:550 [inline]
sk_prot_alloc+0x19c/0x2e0 net/core/sock.c:1477
sk_alloc+0xd7/0x1690 net/core/sock.c:1531
nr_create+0xb9/0x5e0 net/netrom/af_netrom.c:436
__sock_create+0x532/0x930 net/socket.c:1277
sock_create net/socket.c:1317 [inline]
__sys_socket+0x106/0x260 net/socket.c:1347
__do_sys_socket net/socket.c:1356 [inline]
__se_sys_socket net/socket.c:1354 [inline]
__x64_sys_socket+0x73/0xb0 net/socket.c:1354
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290

Freed by task 18466:
save_stack+0x45/0xd0 mm/kasan/common.c:73
set_track mm/kasan/common.c:85 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:458
kasan_slab_free+0xe/0x10 mm/kasan/common.c:466
__cache_free mm/slab.c:3487 [inline]
kfree+0xcf/0x230 mm/slab.c:3806
sk_prot_free net/core/sock.c:1514 [inline]
__sk_destruct+0x76d/0xa60 net/core/sock.c:1596
sk_destruct+0x7b/0x90 net/core/sock.c:1604
__sk_free+0xce/0x300 net/core/sock.c:1615
sk_free+0x42/0x50 net/core/sock.c:1626
sock_put include/net/sock.h:1707 [inline]
nr_release+0x337/0x3c0 net/netrom/af_netrom.c:557
__sock_release+0xd3/0x250 net/socket.c:579
sock_close+0x1b/0x30 net/socket.c:1141
__fput+0x3c5/0xb10 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x1f4/0x2b0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x32a/0x3b0 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x696/0x800 arch/x86/entry/common.c:293

The buggy address belongs to the object at ffff8880a63cec80
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1016 bytes inside of
2048-byte region [ffff8880a63cec80, ffff8880a63cf480)
The buggy address belongs to the page:
page:ffffea000298f380 count:1 mapcount:0 mapping:ffff88812c3f0c40 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea000127f888 ffffea00013a3188 ffff88812c3f0c40
raw: 0000000000000000 ffff8880a63ce400 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a63cef00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a63cef80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a63cf000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a63cf080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a63cf100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

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