Re: [PATCH] staging: android: ion: check for kref overflow

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Aug 20, 2018 at 06:30:57PM -0700, Daniel Rosenberg wrote:
> Userspace can cause the kref to handles to increment
> arbitrarily high. Ensure it does not overflow.
> 
> Signed-off-by: Daniel Rosenberg <drosen@google.com>
> ---
> 
> This patch is against 4.4. It does not apply to master due to a large
> rework of ion in 4.12 which removed the affected functions altogther.
> It applies from 3.18 to 4.11, although with a trivial conflict resolution
> for the later branches.
> 4c23cbff073f3b9b ("staging: android: ion: Remove import interface")
> 
>  drivers/staging/android/ion/ion.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index 374f840f31a48..11f93a6314fdb 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -15,6 +15,7 @@
>   *
>   */
>  
> +#include <linux/atomic.h>
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/file.h>
> @@ -387,6 +388,15 @@ static void ion_handle_get(struct ion_handle *handle)
>  	kref_get(&handle->ref);
>  }
>  
> +/* Must hold the client lock */
> +static struct ion_handle *ion_handle_get_check_overflow(
> +					struct ion_handle *handle)
> +{
> +	if (atomic_read(&handle->ref.refcount) + 1 == 0)
> +		return ERR_PTR(-EOVERFLOW);
> +	ion_handle_get(handle);
> +	return handle;
> +}
> +
>  static int ion_handle_put_nolock(struct ion_handle *handle)
>  {
>  	int ret;

I tried to apply this patch, but it looks like you hand-edited it which
made it impossible to apply.  Did you do that, or did git really create
this broken diff exactly as-is?

Try applying this patch yourself, you will see the error.  I could fix
it by manually editing the diff metadata but I really shouldn't have to
as that implies you did not test the patch you sent me :(

thanks,

greg k-h