Re: [PATCH v5 17/29] iommufd: Add mmap interface

On Fri, May 30, 2025 at 09:59:36AM -0700, Nicolin Chen wrote:

quoted

quoted

+/* The vm_pgoff must be pre-allocated from mt_mmap, and given to user space */
+static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct iommufd_ctx *ictx = filp->private_data;
+	size_t length = vma->vm_end - vma->vm_start;
+	struct iommufd_mmap *immap;
+	int rc;
+
+	if (!PAGE_ALIGNED(length))
+		return -EINVAL;
+	if (!(vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+	if (vma->vm_flags & VM_EXEC)
+		return -EPERM;
+
+	/* vma->vm_pgoff carries an index to an mtree entry (immap) */
+	immap = mtree_load(&ictx->mt_mmap, vma->vm_pgoff);
+	if (!immap)
+		return -ENXIO;
+	/* Validate the vm_pgoff and length against the registered region */
+	if (vma->vm_pgoff != immap->startp)
+		return -ENXIO;

This check seems redundant

Hmm, I was trying to follow your remarks:
"This needs to validate that vm_pgoff is at the start of the immap"
https://lore.kernel.org/all/20250515164717.GL382960@nvidia.com/ (local)

Oh, right I forgot how mtree_load works again. :\ Maybe add a little
note

/* mtree_load returns the immap for any contained pgoff, only allow
   the immap thing to be mapped. */

Jason