From: Hyunwoo Kim <imv4bel@gmail.com>
To: ChenXiaoSong <chenxiaosong2@huawei.com>
Cc: steve.glendinning@shawell.net, deller@gmx.de,
linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
"zhangxiaoxu (A)" <zhangxiaoxu5@huawei.com>,
yangerkun@huawei.com, imv4bel@gmail.com
Subject: Re: Question about patch "fbdev: smscufx: Fix use-after-free in ufx_ops_open()"
Date: Tue, 11 Oct 2022 08:34:36 -0700 [thread overview]
Message-ID: <20221011153436.GA4446@ubuntu> (raw)
In-Reply-To: <363cdfe4-f54d-0ce4-2f03-bcfe998deeef@huawei.com>
On Tue, Oct 11, 2022 at 10:13:02PM +0800, ChenXiaoSong wrote:
> Hi Hyunwoo:
>
> [patch "fbdev: smscufx: Fix use-after-free in ufx_ops_open()"](https://lore.kernel.org/all/20220925133243.GA383897@ubuntu/T/)
> fix [CVE-2022-41849](https://nvd.nist.gov/vuln/detail/CVE-2022-41849).
>
> If the UAF scenarios is as follows, it seems that [fix path
> v3](https://lore.kernel.org/all/20220925133243.GA383897@ubuntu/T/) will not
> avoid race contidion of krefs:
>
> ```
> cpu0 | cpu1
> -------------------------------------|---------------------------------------------------
> 1. open() |
> ufx_ops_open() |
> -------------------------------------|---------------------------------------------------
> | 2. ufx_usb_disconnect()
> | dev->virtualized = true;
> | atomic_set()
> | usb_set_intfdata()
> |
> | 3. if (dev->fb_count == 0)
> | schedule_delayed_work()
> | kref_put() <- kref count : 1
> | kref_put() <- kref count : 0
> | ufx_free()
> | kfree(dev);
> -------------------------------------|---------------------------------------------------
> 4. if (dev->virtualized) <==== UAF |
> ```
You are right. This v3 fix patch may prevent the UAF scenario I first suggested,
but not the one you suggested.
Any good ideas for this?
Could it be solved by adding a global flag variable indicating disconnected?
Regards,
Hyunwoo Kim.
WARNING: multiple messages have this Message-ID (diff)
From: Hyunwoo Kim <imv4bel@gmail.com>
To: ChenXiaoSong <chenxiaosong2@huawei.com>
Cc: steve.glendinning@shawell.net, linux-fbdev@vger.kernel.org,
yangerkun@huawei.com, dri-devel@lists.freedesktop.org,
imv4bel@gmail.com, "zhangxiaoxu \(A\)" <zhangxiaoxu5@huawei.com>,
deller@gmx.de
Subject: Re: Question about patch "fbdev: smscufx: Fix use-after-free in ufx_ops_open()"
Date: Tue, 11 Oct 2022 08:34:36 -0700 [thread overview]
Message-ID: <20221011153436.GA4446@ubuntu> (raw)
In-Reply-To: <363cdfe4-f54d-0ce4-2f03-bcfe998deeef@huawei.com>
On Tue, Oct 11, 2022 at 10:13:02PM +0800, ChenXiaoSong wrote:
> Hi Hyunwoo:
>
> [patch "fbdev: smscufx: Fix use-after-free in ufx_ops_open()"](https://lore.kernel.org/all/20220925133243.GA383897@ubuntu/T/)
> fix [CVE-2022-41849](https://nvd.nist.gov/vuln/detail/CVE-2022-41849).
>
> If the UAF scenarios is as follows, it seems that [fix path
> v3](https://lore.kernel.org/all/20220925133243.GA383897@ubuntu/T/) will not
> avoid race contidion of krefs:
>
> ```
> cpu0 | cpu1
> -------------------------------------|---------------------------------------------------
> 1. open() |
> ufx_ops_open() |
> -------------------------------------|---------------------------------------------------
> | 2. ufx_usb_disconnect()
> | dev->virtualized = true;
> | atomic_set()
> | usb_set_intfdata()
> |
> | 3. if (dev->fb_count == 0)
> | schedule_delayed_work()
> | kref_put() <- kref count : 1
> | kref_put() <- kref count : 0
> | ufx_free()
> | kfree(dev);
> -------------------------------------|---------------------------------------------------
> 4. if (dev->virtualized) <==== UAF |
> ```
You are right. This v3 fix patch may prevent the UAF scenario I first suggested,
but not the one you suggested.
Any good ideas for this?
Could it be solved by adding a global flag variable indicating disconnected?
Regards,
Hyunwoo Kim.
next prev parent reply other threads:[~2022-10-11 15:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-11 14:13 Question about patch "fbdev: smscufx: Fix use-after-free in ufx_ops_open()" ChenXiaoSong
2022-10-11 14:13 ` ChenXiaoSong
2022-10-11 15:34 ` Hyunwoo Kim [this message]
2022-10-11 15:34 ` Hyunwoo Kim
2022-10-20 20:05 ` Hyunwoo Kim
2022-10-20 20:05 ` Hyunwoo Kim
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221011153436.GA4446@ubuntu \
--to=imv4bel@gmail.com \
--cc=chenxiaosong2@huawei.com \
--cc=deller@gmx.de \
--cc=dri-devel@lists.freedesktop.org \
--cc=linux-fbdev@vger.kernel.org \
--cc=steve.glendinning@shawell.net \
--cc=yangerkun@huawei.com \
--cc=zhangxiaoxu5@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.