syzbot found the following crash on:

HEAD commit:    e1ef035d272e Merge tag 'armsoc-defconfig' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1674b0bb400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9c6a26e22579190b
dashboard link: https://syzkaller.appspot.com/bug?extid=500c69d1e21d970e461b
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:
Reported-by: syzbot+500c69d1e21d970e4...@syzkaller.appspotmail.com

IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
audit: type=1400 audit(1546374052.492:5134): avc: denied { map } for pid=30025 comm="blkid" path="/sbin/blkid" dev="sda1" ino=16128 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x62d/0x7d0 include/trace/events/lock.h:13
Read of size 8 at addr ffff88804fb90e78 by task syz-executor3/30043

CPU: 1 PID: 30043 Comm: syz-executor3 Not tainted 4.20.0+ #3
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
 perf_trace_lock_acquire+0x62d/0x7d0 include/trace/events/lock.h:13
 trace_lock_acquire include/trace/events/lock.h:13 [inline]
 lock_acquire+0x371/0x570 kernel/locking/lockdep.c:3840
audit: type=1400 audit(1546374052.492:5135): avc: denied { map } for pid=30025 comm="blkid" path="/lib/x86_64-linux-gnu/libblkid.so.1.1.0" dev="sda1" ino=2825 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
 _raw_spin_lock_bh+0x33/0x50 kernel/locking/spinlock.c:168
audit: type=1400 audit(1546374052.502:5136): avc: denied { map } for pid=30024 comm="modprobe" path="/bin/kmod" dev="sda1" ino=1440 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
 spin_lock_bh include/linux/spinlock.h:334 [inline]
 lock_sock_nested+0x41/0x120 net/core/sock.c:2780
 lock_sock include/net/sock.h:1502 [inline]
 nr_connect+0xc77/0x1380 net/netrom/af_netrom.c:743
 __sys_connect+0x357/0x490 net/socket.c:1664
 __do_sys_connect net/socket.c:1675 [inline]
 __se_sys_connect net/socket.c:1672 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1672
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
RIP: 0033:0x457ec9
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:00007f3f0371fc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457ec9
RDX: 0000000000000048 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3f037206d4
R13: 00000000004be35a R14: 00000000004ce5e8 R15: 00000000ffffffff

Allocated by task 30040:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 kasan_kmalloc mm/kasan/common.c:482 [inline]
 kasan_kmalloc+0xcf/0xe0 mm/kasan/common.c:455
 __do_kmalloc mm/slab.c:3709 [inline]
 __kmalloc+0x15c/0x740 mm/slab.c:3718
 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
audit: type=1400 audit(1546374052.502:5137): avc: denied { map } for pid=30024 comm="modprobe" path="/bin/kmod" dev="sda1" ino=1440 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
 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 30035:
 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:444
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
 __cache_free mm/slab.c:3485 [inline]
 kfree+0xcf/0x230 mm/slab.c:3804
 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:1703 [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 ffff88804fb90dc0
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 184 bytes inside of
 2048-byte region [ffff88804fb90dc0, ffff88804fb915c0)
IPVS: ftp: loaded support on port[0] = 21
The buggy address belongs to the page:
page:ffffea00013ee400 count:1 mapcount:0 mapping:ffff88812c3f0c40 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00015f8b88 ffffea00025b1908 ffff88812c3f0c40
raw: 0000000000000000 ffff88804fb90540 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88804fb90d00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
 ffff88804fb90d80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff88804fb90e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804fb90e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804fb90f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
kobject: 'lo' (0000000050df09a4): kobject_add_internal: parent: 'net', set: 'devices'

This bug is generated by a bot. It may contain errors.
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