KASAN: use-after-free Write in rtl_fw_do_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    3ed8e1c2 usb: typec: tcpm: Migrate workqueue to RT priorit..
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=111f9015900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ccafc70ac3d5f49c
dashboard link: https://syzkaller.appspot.com/bug?extid=dc3cab055dff074f2d7f
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=148a00c9900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dc3cab055dff074f2d7f@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: Direct firmware load for rtlwifi/rtl8192cufw_TMSC.bin failed with error -2
usb 1-1: Direct firmware load for rtlwifi/rtl8192cufw.bin failed with error -2
rtlwifi: Loading alternative firmware rtlwifi/rtl8192cufw.bin
rtlwifi: Selected firmware is not available
==================================================================
BUG: KASAN: use-after-free in rtl_fw_do_work.cold+0x68/0x6a drivers/net/wireless/realtek/rtlwifi/core.c:93
Write of size 4 at addr ffff8881c9c2ff30 by task kworker/1:5/3063

CPU: 1 PID: 3063 Comm: kworker/1:5 Not tainted 5.9.0-rc1-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.cold+0x68/0x6a drivers/net/wireless/realtek/rtlwifi/core.c:93
 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:000000008323bb9d refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1c9c2f
flags: 0x200000000000000()
raw: 0200000000000000 0000000000000000 ffffea0007270bc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c9c2fe00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881c9c2fe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881c9c2ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                     ^
 ffff8881c9c2ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881c9c30000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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