From: Wei Liu <wei.liu@kernel.org>
To: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Cc: kys@microsoft.com, haiyangz@microsoft.com,
sthemmin@microsoft.com, wei.liu@kernel.org,
linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] video/fbdev: Fix a double free in hvfb_probe
Date: Tue, 23 Mar 2021 11:28:38 +0000 [thread overview]
Message-ID: <20210323112838.xrastmol4fnxqxub@liuwe-devbox-debian-v2> (raw)
In-Reply-To: <20210323073350.17697-1-lyl2019@mail.ustc.edu.cn>
Thanks for your patch.
I would like to change the prefix to "video: hyperv_fb:" to be more
specific.
On Tue, Mar 23, 2021 at 12:33:50AM -0700, Lv Yunlong wrote:
> 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 twice
> by framebuffer_release(info).
>
I would say "freed for the second time" here. What you wrote reads to me
fraembuffer_release frees the buffer twice all by itself.
> My patch sets info->apertures to NULL after it was freed to avoid
> double free.
>
I think this approach works. I would like to give other people a chance
to comment though.
Fixes: 3a6fb6c4255c ("video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.")
> Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> ---
> drivers/video/fbdev/hyperv_fb.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
> index c8b0ae676809..2fc9b507e73a 100644
> --- a/drivers/video/fbdev/hyperv_fb.c
> +++ b/drivers/video/fbdev/hyperv_fb.c
> @@ -1032,6 +1032,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
> if (!pdev) {
> pr_err("Unable to find PCI Hyper-V video\n");
> kfree(info->apertures);
> + info->apertures = NULL;
> return -ENODEV;
> }
>
> @@ -1130,6 +1131,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
> pci_dev_put(pdev);
> }
> kfree(info->apertures);
> + info->apertures = NULL;
>
> return 0;
>
> @@ -1142,6 +1144,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
> if (!gen2vm)
> pci_dev_put(pdev);
> kfree(info->apertures);
> + info->apertures = NULL;
>
> return -ENOMEM;
> }
> --
> 2.25.1
>
>
next prev parent reply other threads:[~2021-03-23 11:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-23 7:33 [PATCH] video/fbdev: Fix a double free in hvfb_probe Lv Yunlong
2021-03-23 11:28 ` Wei Liu [this message]
2021-03-23 18:52 ` Michael Kelley
2021-03-24 10:24 ` lyl2019
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