[PATCH 2/6] mm: introduce vma_set_file function v3

[Jason Gunthorpe]

On Fri, Oct 09, 2020 at 05:03:38PM +0200, Christian König wrote:
> +/*
> + * Change backing file, only valid to use during initial VMA setup.
> + */
> +void vma_set_file(struct vm_area_struct *vma, struct file *file)
> +{
> +	if (file)
> +	        get_file(file);
> +
> +	swap(vma->vm_file, file);
> +
> +	if (file)
> +		fput(file);
> +}

fput crashes when file is NULL so the error handling after
unmap_and_free_vma: can't handle this case, similarly vm_file can't be
NULL either.

So just simply:

 swap(vma->vm_file, file);
 get_file(vma->vm_file);
 fput(file);
 
Will do?

Just let it crash if any of them are wrongly NULL.

Jason