Re: [PATCH 03/13] drm/vkms: Extract vkms_config header

Louis Chauvet
2025-01-30T13:48:22Z

On 29/01/25 - 12:00, José Expósito wrote:
> Creating a new vkms_config structure will be more complex once we
> start adding more options.
>
> Extract the vkms_config structure to its own header and source files
> and add functions to create and delete a vkms_config and to initialize
> debugfs.
>
> Refactor, no functional changes.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>

Co-developped-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>

[...]

> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -208,8 +189,7 @@ static int vkms_create(struct vkms_config *config)
> if (ret)
> goto out_devres;
>
> - drm_debugfs_add_files(&vkms_device->drm, vkms_config_debugfs_list,
> - ARRAY_SIZE(vkms_config_debugfs_list));
> + vkms_config_register_debugfs(vkms_device);
>
> ret = drm_dev_register(&vkms_device->drm, 0);
> if (ret)
> @@ -231,9 +211,9 @@ static int __init vkms_init(void)
> int ret;
> struct vkms_config *config;
>
> - config = kmalloc(sizeof(*config), GFP_KERNEL);
> - if (!config)
> - return -ENOMEM;
> + config = vkms_config_create();
> + if (IS_ERR(config))
> + return PTR_ERR(config);
>
> default_config = config;
>
> @@ -243,7 +223,7 @@ static int __init vkms_init(void)
>
> ret = vkms_create(config);
> if (ret)
> - kfree(config);
> + vkms_config_destroy(config);

I just have a question here: is it not a problem to kfree config (and
default_config) here? There is not risk to have a
use-after-free/double-free in vkms_exit?

> return ret;
> }
> @@ -272,7 +252,7 @@ static void __exit vkms_exit(void)
> if (default_config->dev)

The use-after-free may be here?

> vkms_destroy(default_config);
>
> - kfree(default_config);
> + vkms_config_destroy(default_config);

And maybe double-free?

> }

If this is not an issue (ie we have a garantee that vkms_exit is never
called if vkms_init fails), you can add my

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com> …