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Date: Mon, 21 Nov 2022 07:39:20 -0300
From: Thadeu Lima de Souza Cascardo <>
Subject: Re: Linux kernel: staging: rtl8712: A
 Use-after-Free/Double-Free bug in read_bbreg_hdl in

On Fri, Nov 18, 2022 at 11:58:55AM +0800, Zheng Hacker wrote:
> hi,
> This is a bug I've found in linux kernel before 5.19.2, which is
> in cmd_hdl_filter in drivers/staging/rtl8712/rtl8712_cmd.c, allows
> attacker to launch Local Denial of Service attack and gain escalation
> of privileges.
> I reported it to linux kernel in 2022.8.29 and the upstream fixed it in
> 2022.09.06. Now the patch was opened to the public
> ## Root cause && possible exploit
> This is a uaf / double free bug. Whenrtl8712 wireless networdk adapter
> initialized, for example using command "ifconfig wlan0 up",
> it calls netdev_open function, which final calls cmd_hdl_filter function.
> As we can control the command code, we can trigger the vulnerabiliy.
> After pcmd object was freed, we can use msg_msg heap spray to
> get the object, and design the layout of it. By controlling the parambuf
> address, we can leak infomation to pcmbuf, which will finally write to
> adapater's memory. By using msg_msg tech we can also leak the information.
> Then in r8712_free_cmd_obj funtion , as we have access to pcmd->parmbuf. Now
> we have a Arbitrary Free bug. This is a powerful primitive and there is some
> common skill after that.
> ## Fix
> [1]
> [2]
> ## CVE
> Now no CVE number is assigned for this issue.

This was assigned CVE-2022-4095.


> ## Timeline
> 2022-08-29: reported to
> 2022-08-29: bug confirmed
> 2022-09-06: patch it
> 2022-09-06: patch released
> 2022-09-07: apply for a CVE number in MITRE
> 2022-09-29: reported to
> 2022-11-18: Announced on oss-security lists.
> ## Credit
> Zheng Wang(@xmzyshypnc) and Zhuorao Yang(@A1ex)
> ## Additional Information
> This is a bug reported to Linux kernel. Although staging driver is not
> a so important driver module in Linux. [1] This vulnerability has been
> introduced as far as the driver was added in 2010. I've checked the
> issue doesn't affect the vendor in the CNA-project list. But this
> issue can affect othe company who use it as their rtl8712 adapter
> driver module like D-link [2] . I  searched the related issue like
> CVE-2021-28660. I think its NOTE description(NOTE: from the
> perspective of releases, CVE IDs are not normally used for
> drivers/staging/* (unfinished work); however, system integrators may
> have situations in which a drivers/staging issue is relevant to their
> own customer base) is very appropriate for my situation.  This is a
> long-existing issue as far as the driver module was added so I think
> it's necessary to assign a CVE number so that anyone using it can fix
> the bug.
> [1]
> [2]
> Best regards,
> Zheng Wang

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