Hi,
good catch
On 3/23/21 3:46 AM, Lv Yunlong wrote:
> In function displback_changed, has the call chain
> displback_connect(front_info)->xen_drm_drv_init(front_info).
> We can see that drm_info is assigned to front_info->drm_info
> and drm_info is freed in fail branch in xen_drm_drv_init().
>
> Later displback_disconnect(front_info) is called and it calls
> xen_drm_drv_fini(front_info) cause a use after free by
> drm_info = front_info->drm_info statement.
>
> My patch has done two things. First fixes the fail label which
> drm_info = kzalloc() failed and still free the drm_info.
> Second sets front_info->drm_info to NULL to avoid uaf.
>
> Signed-off-by: Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx>
Thank you for the patch,
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
Will apply to drm-misc-next-fixes
Thank you,
Oleksandr
> ---
> drivers/gpu/drm/xen/xen_drm_front.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
> index 30d9adf31c84..9f14d99c763c 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
> @@ -521,7 +521,7 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
> drm_dev = drm_dev_alloc(&xen_drm_driver, dev);
> if (IS_ERR(drm_dev)) {
> ret = PTR_ERR(drm_dev);
> - goto fail;
> + goto fail_dev;
> }
>
> drm_info->drm_dev = drm_dev;
> @@ -551,8 +551,10 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
> drm_kms_helper_poll_fini(drm_dev);
> drm_mode_config_cleanup(drm_dev);
> drm_dev_put(drm_dev);
> -fail:
> +fail_dev:
> kfree(drm_info);
> + front_info->drm_info = NULL;
> +fail:
> return ret;
> }
>
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