Re: [linux-next PATCH v4] drivers/virt/fsl_hypervisor: Fix error handling path

[John Hubbard]

On 9/1/20 2:21 PM, Souptick Joarder wrote:
> First, when memory allocation for sg_list_unaligned failed, there
> is a bug of calling put_pages() as we haven't pinned any pages.
>
> Second, if get_user_pages_fast() failed we should unpin num_pinned
> pages.
>
> This will address both.
>
> As part of these changes, minor update in documentation.
>
> Fixes: 6db7199407ca ("drivers/virt: introduce Freescale hypervisor
> management driver")
> Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---

This looks good to me.

thanks,
--
John Hubbard
NVIDIA

> v2:
>     Added review tag.
>
> v3:
>     Address review comment on v2 from John.
>     Added review tag.
>
> v4:
>    Address another set of review comments from John.
>
>   drivers/virt/fsl_hypervisor.c | 17 ++++++++---------
>   1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/virt/fsl_hypervisor.c b/drivers/virt/fsl_hypervisor.c
> index 1b0b11b..46ee0a0 100644
> --- a/drivers/virt/fsl_hypervisor.c
> +++ b/drivers/virt/fsl_hypervisor.c
> @@ -157,7 +157,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>   
>   	unsigned int i;
>   	long ret = 0;
> -	int num_pinned; /* return value from get_user_pages() */
> +	int num_pinned = 0; /* return value from get_user_pages_fast() */
>   	phys_addr_t remote_paddr; /* The next address in the remote buffer */
>   	uint32_t count; /* The number of bytes left to copy */
>   
> @@ -174,7 +174,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>   		return -EINVAL;
>   
>   	/*
> -	 * The array of pages returned by get_user_pages() covers only
> +	 * The array of pages returned by get_user_pages_fast() covers only
>   	 * page-aligned memory.  Since the user buffer is probably not
>   	 * page-aligned, we need to handle the discrepancy.
>   	 *
> @@ -224,7 +224,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>   
>   	/*
>   	 * 'pages' is an array of struct page pointers that's initialized by
> -	 * get_user_pages().
> +	 * get_user_pages_fast().
>   	 */
>   	pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
>   	if (!pages) {
> @@ -241,7 +241,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>   	if (!sg_list_unaligned) {
>   		pr_debug("fsl-hv: could not allocate S/G list\n");
>   		ret = -ENOMEM;
> -		goto exit;
> +		goto free_pages;
>   	}
>   	sg_list = PTR_ALIGN(sg_list_unaligned, sizeof(struct fh_sg_list));
>   
> @@ -250,7 +250,6 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>   		num_pages, param.source != -1 ? FOLL_WRITE : 0, pages);
>   
>   	if (num_pinned != num_pages) {
> -		/* get_user_pages() failed */
>   		pr_debug("fsl-hv: could not lock source buffer\n");
>   		ret = (num_pinned < 0) ? num_pinned : -EFAULT;
>   		goto exit;
> @@ -292,13 +291,13 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>   		virt_to_phys(sg_list), num_pages);
>   
>   exit:
> -	if (pages) {
> -		for (i = 0; i < num_pages; i++)
> -			if (pages[i])
> -				put_page(pages[i]);
> +	if (pages && (num_pinned > 0)) {
> +		for (i = 0; i < num_pinned; i++)
> +			put_page(pages[i]);
>   	}
>   
>   	kfree(sg_list_unaligned);
> +free_pages:
>   	kfree(pages);
>   
>   	if (!ret)