Subject: CVE-2021-47479: staging: rtl8712: fix use-after-free in rtl8712_dl_fw

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

staging: rtl8712: fix use-after-free in rtl8712_dl_fw

Syzbot reported use-after-free in rtl8712_dl_fw(). The problem was in
race condition between r871xu_dev_remove() ->ndo_open() callback.

It's easy to see from crash log, that driver accesses released firmware
in ->ndo_open() callback. It may happen, since driver was releasing
firmware _before_ unregistering netdev. Fix it by moving
unregister_netdev() before cleaning up resources.

Call Trace:
...
 rtl871x_open_fw drivers/staging/rtl8712/hal_init.c:83 [inline]
 rtl8712_dl_fw+0xd95/0xe10 drivers/staging/rtl8712/hal_init.c:170
 rtl8712_hal_init drivers/staging/rtl8712/hal_init.c:330 [inline]
 rtl871x_hal_init+0xae/0x180 drivers/staging/rtl8712/hal_init.c:394
 netdev_open+0xe6/0x6c0 drivers/staging/rtl8712/os_intfs.c:380
 __dev_open+0x2bc/0x4d0 net/core/dev.c:1484

Freed by task 1306:
...
 release_firmware+0x1b/0x30 drivers/base/firmware_loader/main.c:1053
 r871xu_dev_remove+0xcc/0x2c0 drivers/staging/rtl8712/usb_intf.c:599
 usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:458

The Linux kernel CVE team has assigned CVE-2021-47479 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 3.3 with commit 8c213fa59199 and fixed in 5.10.79 with commit c430094541a8
	Issue introduced in 3.3 with commit 8c213fa59199 and fixed in 5.14.18 with commit befd23bd3b17
	Issue introduced in 3.3 with commit 8c213fa59199 and fixed in 5.15.2 with commit a65c9afe9f2f
	Issue introduced in 3.3 with commit 8c213fa59199 and fixed in 5.16 with commit c052cc1a069c
	Issue introduced in 3.2.6 with commit bc5d453eab45

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47479
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/staging/rtl8712/usb_intf.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/c430094541a80575259a94ff879063ef01473506
	https://git.kernel.org/stable/c/befd23bd3b17f1a3f9c943a8580b47444c7c63ed
	https://git.kernel.org/stable/c/a65c9afe9f2f55b7a7fb4a25ab654cd4139683a4
	https://git.kernel.org/stable/c/c052cc1a069c3e575619cf64ec427eb41176ca70