From: Lv Yunlong <lyl2...@mail.ustc.edu.cn> Sent: Tuesday, March 23, 2021 12:34
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 twice
> by framebuffer_release(info).
>
> My patch sets info->apertures to NULL after it was freed to avoid
> double free.
>
> Signed-off-by: Lv Yunlong <lyl2...@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
>
While I think this works, a slightly better solution might be to remove
all calls to kfree(info->apertures) in hvfb_getmem(), and just let
framebuffer_release() handle freeing the memory. That's what is
done in other drivers that follow the fbdev pattern, and it's less
code overall.
Michael
