[openib-general] [PATCH 7/7] IB/ipath - performance improvements via mmap of queues

[Roland Dreier]

 > +/*
 > + * ipath_vma_nopage - handle a VMA page fault.
 > + */
 > +static struct page *ipath_vma_nopage(struct vm_area_struct *vma,
 > +				     unsigned long address, int *type)
 > +{
 > +	struct ipath_mmap_info *ip = vma->vm_private_data;
 > +	unsigned long offset = address - vma->vm_start;
 > +	struct page *page = NOPAGE_SIGBUS;
 > +	void *pageptr;
 > +
 > +	if (offset >= ip->size)
 > +		goto out; /* out of range */
 > +
 > +	/*
 > +	 * Convert the vmalloc address into a struct page.
 > +	 */
 > +	pageptr = (void *)(offset + (vma->vm_pgoff << PAGE_SHIFT));
 > +	page = vmalloc_to_page(pageptr);
 > +	if (!page)
 > +		goto out;
 > +
 > +	/* Increment the reference count. */
 > +	get_page(page);
 > +	if (type)
 > +		*type = VM_FAULT_MINOR;
 > +out:
 > +	return page;
 > +}
 > +
 > +static struct vm_operations_struct ipath_vm_ops = {
 > +	.open =     ipath_vma_open,
 > +	.close =    ipath_vma_close,
 > +	.nopage =   ipath_vma_nopage,
 > +};

It seems that all this would be much simpler with vmalloc_user() and
remap_vmalloc_range().  And it would fix the information leak you
introduce here: I don't see anywhere that you clear the memory you
vmalloc and remap to userspace, so you're potentially exposing the
cached contents of /etc/passwd or something like that.

 - R.