From: Wei Liu <wei.liu@kernel.org>
To: Michael Kelley <mikelley@microsoft.com>
Cc: Lv Yunlong <lyl2019@mail.ustc.edu.cn>,
KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] video: hyperv_fb: Fix a double free in hvfb_probe
Date: Thu, 25 Mar 2021 13:30:36 +0000 [thread overview]
Message-ID: <20210325133036.rbriezf3v32wofkl@liuwe-devbox-debian-v2> (raw)
In-Reply-To: <MWHPR21MB1593F19EE7AD10698582FA78D7639@MWHPR21MB1593.namprd21.prod.outlook.com>
On Wed, Mar 24, 2021 at 01:46:39PM +0000, Michael Kelley wrote:
> From: Lv Yunlong <lyl2019@mail.ustc.edu.cn> Sent: Wednesday, March 24, 2021 3:37 AM
> >
> > In function hvfb_probe in hyperv_fb.c, it calls hvfb_getmem(hdev, info)
> > and return err when info->apertures is freed.
> >
> > In the error1 label of hvfb_probe, info->apertures will be freed for the
> > second time in framebuffer_release(info).
> >
> > My patch removes all kfree(info->apertures) instead of set info->apertures
> > to NULL. It is because that let framebuffer_release() handle freeing the
> > memory flows the fbdev pattern, and less code overall.
>
> Let me suggest some clarifications in the commit message. It's probably
> better not to reference the initial approach of setting info->apertures to
> NULL, since there won't be any record of that approach in the commit
> history. Here's what I would suggest:
>
> Function hvfb_probe() calls hvfb_getmem(), expecting upon return that
> info->apertures is either NULL or points to memory that should be freed
> by framebuffer_release(). But hvfb_getmem() is freeing the memory and
> leaving the pointer non-NULL, resulting in a double free if an error
> occurs or later if hvfb_remove() is called.
>
> Fix this by removing all kfree(info->apertures) calls in hvfb_getmem().
> This will allow framebuffer_release() to free the memory, which follows
> the pattern of other fbdev drivers.
>
> Modulo this revision to the commit message, which Wei Liu can
> probably incorporate,
>
Yes. I surely can incorporate the changes.
I will also add the Fixes tag.
> Reviewed-by: Michael Kelley <mikelley@microsoft.com>
prev parent reply other threads:[~2021-03-25 13:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 10:37 [PATCH v2] video: hyperv_fb: Fix a double free in hvfb_probe Lv Yunlong
2021-03-24 13:46 ` Michael Kelley
2021-03-25 13:30 ` Wei Liu [this message]
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