linux-kernel - Re: [PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm

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Message-ID: <CA+55aFwXn2ak_zjKyVGznYwoCDewHicFYX-ngLtrofDPyQ0N=w@mail.gmail.com>
Date:	Tue, 10 Nov 2015 09:43:03 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Joerg Roedel <joro@...tes.org>
Cc:	"open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
	Oded Gabbay <oded.gabbay@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault()

On Tue, Nov 10, 2015 at 5:26 AM, Joerg Roedel <joro@...tes.org> 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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