Re: [PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault()

[Linus Torvalds]

On Tue, Nov 10, 2015 at 5:26 AM, Joerg Roedel <joro@xxxxxxxxxx> wrote:
> +
> +static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req)
> +{
> +       return !((req->rd_req  && (vma->vm_flags & VM_READ))  ||
> +                (req->wr_req  && (vma->vm_flags & VM_WRITE)) ||
> +                (req->exe_req && (vma->vm_flags & VM_EXEC)));
> +}

This seems odd.

Shouldn't it be

    return ((req->rd_req  && !(vma->vm_flags & VM_READ))  ||
            (req->wr_req  && !(vma->vm_flags & VM_WRITE)) ||
            (req->exe_req && !(vma->vm_flags & VM_EXEC)));

instead?

Of course, if you just used the VM_xyz flags internally itself, this
would all be easier, and you'd end up with something like

    /* Do we have requested bits that aren't in the allowed set? */
    return (requested & ~vma->vm_flags) != 0;

instead..

              Linus
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