KASAN: use-after-free Read in rtl_fw_do_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    449dc8c9 Merge tag 'for-v5.9' of git://git.kernel.org/pub/..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=16cd1a26900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6ef84fa8ee48e528
dashboard link: https://syzkaller.appspot.com/bug?extid=ff4b26b0bfbff2dc7960
compiler:       gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ff4b26b0bfbff2dc7960@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 5-1: Direct firmware load for rtlwifi/rtl8192cufw.bin failed with error -2
==================================================================
BUG: KASAN: use-after-free in rtl_fw_do_work+0x407/0x430 drivers/net/wireless/realtek/rtlwifi/core.c:87
Read of size 8 at addr ffff8881cd72ff38 by task kworker/1:5/3068

CPU: 1 PID: 3068 Comm: kworker/1:5 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events request_firmware_work_func
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xf6/0x16e lib/dump_stack.c:118
 print_address_description.constprop.0+0x1c/0x210 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x37/0x7c mm/kasan/report.c:530
 rtl_fw_do_work+0x407/0x430 drivers/net/wireless/realtek/rtlwifi/core.c:87
 request_firmware_work_func+0x126/0x250 drivers/base/firmware_loader/main.c:1001
 process_one_work+0x94c/0x15f0 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x392/0x470 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the page:
page:000000004712885d refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1cd72f
flags: 0x200000000000000()
raw: 0200000000000000 0000000000000000 ffffea000735cbc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881cd72fe00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881cd72fe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881cd72ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff8881cd72ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881cd730000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.