Re: [PATCH] tee/tee_shm.c: Fix error handling path

[Jens Wiklander]

On Sun, Sep 13, 2020 at 10:12:11AM +0530, Souptick Joarder wrote:
> When shm->num_pages <= 0, we should avoid calling
> release_registered_pages() in error handling path.
What are we fixing?

> 
> Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>  drivers/tee/tee_shm.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 00472f5..e517d9f 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -260,8 +260,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
>  		rc = get_kernel_pages(kiov, num_pages, 0, shm->pages);
>  		kfree(kiov);
>  	}
> -	if (rc > 0)
> -		shm->num_pages = rc;
> +	shm->num_pages = rc;
Why not avoiding assigning invalid values to shm->num_pages?
By the way, shm->num_pages is a size_t.

>  	if (rc != num_pages) {
>  		if (rc >= 0)
>  			rc = -ENOMEM;
> @@ -309,7 +308,9 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
>  			idr_remove(&teedev->idr, shm->id);
>  			mutex_unlock(&teedev->mutex);
>  		}
> -		release_registered_pages(shm);
> +		if (shm->pages && (shm->num_pages > 0))
> +			release_registered_pages(shm);
> +
With this we'll leak if shm->pages has been assigned something.

>  	}
>  	kfree(shm);
>  	teedev_ctx_put(ctx);
> -- 
> 1.9.1
> 

Thanks,
Jens