Re: [PATCH v2 1/1] firmware_loader: Fix use-after-free during unregister

[matthew . gerlach]

On Mon, 29 Aug 2022, Russ Weight wrote:

> In the following code within firmware_upload_unregister(), the call to
> device_unregister() could result in the dev_release function freeing the
> fw_upload_priv structure before it is dereferenced for the call to
> module_put(). This bug was found by the kernel test robot using
> CONFIG_KASAN while running the firmware selftests.
>
>  device_unregister(&fw_sysfs->dev);
>  module_put(fw_upload_priv->module);
>
> The problem is fixed by copying fw_upload_priv->module to a local variable
> for use when calling device_unregister().
>
> Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> Fixes: 97730bbb242c ("firmware_loader: Add firmware-upload support")
> Signed-off-by: Russ Weight <russell.h.weight@xxxxxxxxx>

Looks good to me.

Reviewed-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> ---
> v2: Rebased to latest linux-next branch (next-20220829)
> ---
> drivers/base/firmware_loader/sysfs_upload.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/firmware_loader/sysfs_upload.c b/drivers/base/firmware_loader/sysfs_upload.c
> index 87044d52322a..63e15bddd80c 100644
> --- a/drivers/base/firmware_loader/sysfs_upload.c
> +++ b/drivers/base/firmware_loader/sysfs_upload.c
> @@ -377,6 +377,7 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
> {
> 	struct fw_sysfs *fw_sysfs = fw_upload->priv;
> 	struct fw_upload_priv *fw_upload_priv = fw_sysfs->fw_upload_priv;
> +	struct module *module = fw_upload_priv->module;
>
> 	mutex_lock(&fw_upload_priv->lock);
> 	if (fw_upload_priv->progress == FW_UPLOAD_PROG_IDLE) {
> @@ -392,6 +393,6 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
>
> unregister:
> 	device_unregister(&fw_sysfs->dev);
> -	module_put(fw_upload_priv->module);
> +	module_put(module);
> }
> EXPORT_SYMBOL_GPL(firmware_upload_unregister);
> --
> 2.25.1