[PATCH] staging: greybus: use after free in gb_audio_manager_remove_all()

[Vaibhav Agarwal]

On Wed, Feb 5, 2020 at 6:02 PM Dan Carpenter <dan.carpenter at oracle.com> wrote:
>
> When we call kobject_put() and it's the last reference to the kobject
> then it calls gb_audio_module_release() and frees module.  We dereference
> "module" on the next line which is a use after free.
>
> Fixes: c77f85bbc91a ("greybus: audio: Fix incorrect counting of 'ida'")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
> ---
>  drivers/staging/greybus/audio_manager.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/greybus/audio_manager.c b/drivers/staging/greybus/audio_manager.c
> index 9b19ea9d3fa1..9a3f7c034ab4 100644
> --- a/drivers/staging/greybus/audio_manager.c
> +++ b/drivers/staging/greybus/audio_manager.c
> @@ -92,8 +92,8 @@ void gb_audio_manager_remove_all(void)
>
>         list_for_each_entry_safe(module, next, &modules_list, list) {
>                 list_del(&module->list);
> -               kobject_put(&module->kobj);
>                 ida_simple_remove(&module_id, module->id);
> +               kobject_put(&module->kobj);
>         }
>
>         is_empty = list_empty(&modules_list);
> --
> 2.11.0
>
Thanks Dan for sharing the fix.

Reviewed-by: Vaibhav Agarwal <vaibhav.sr at gmail.com>