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Re: [Xen-devel] [PATCH 4.1] x86: fix emuirq regression from XSA-21 fix



Jan Beulich wrote:
On 25.06.13 at 07:33, DuanZhenzhong <zhenzhong.duan@xxxxxxxxxx> wrote:
Stefano Stabellini wrote:
On Mon, 24 Jun 2013, Zhenzhong Duan wrote:
Could you have a look if there is something wrong in xen side of clearing the mapping?
What I am saying is that the error you are getting:

pt_msix_disable: Unbind msix with pirq 67, gvec 0
pt_msix_disable: Unmap msix with pirq 67
pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]

cannot be caused by domain_pirq_to_emuirq(d, pirq) returning
IRQ_UNBOUND.
So, why are you getting this error? What is failing?
I am ready to believe the problem is in Xen but Without understanding
why you are getting the error it's hard to find a solution.
I found the reason, you are looking at xen-unstable, I was working with 4.1.30-OVM, it has patch of CVE-2012-4536 / XSA-21. That patch set ret to -EINVAL initially. After remove that line, unmap succeed.

Removing that line certainly isn't right. The proper fix is the one
below/attached.

Jan

****************************************************
x86: fix emuirq regression from XSA-21 fix

The XSA-21 patch broke the assumption of "ret" being zero prior to the
IRQ_UNBOUND check.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/physdev.c
+++ b/xen/arch/x86/physdev.c
@@ -243,6 +243,8 @@ static int physdev_unmap_pirq(struct phy
         spin_lock(&d->event_lock);
         if ( domain_pirq_to_emuirq(d, unmap->pirq) != IRQ_UNBOUND )
             ret = unmap_domain_pirq_emuirq(d, unmap->pirq);
+        else
+            ret = 0;
         spin_unlock(&d->event_lock);
         if ( unmap->domid == DOMID_SELF || ret )
             goto free_domain;



Any reason of not right? below patch does work as ret is already zero if it 
could get to that line.

zduan

****************************************************
x86: fix emuirq regression from XSA-21 fix

The XSA-21 patch broke the assumption of "ret" being zero prior to the
IRQ_UNBOUND check.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>

--- a/xen/arch/x86/physdev.c
+++ b/xen/arch/x86/physdev.c
@@ -240,7 +240,6 @@ static int physdev_unmap_pirq(struct phy
    if ( ret )
        return ret;

-    ret = -EINVAL;
    if ( unmap->pirq < 0 || unmap->pirq >= d->nr_pirqs )
        goto free_domain;



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