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Re: [Xen-devel] [PATCH v6 02/11] arch, arm: add consistency check to REMOVE p2m changes
- To: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxx
- From: Julien Grall <julien.grall@xxxxxxxxxx>
- Date: Tue, 22 Apr 2014 20:35:30 +0100
- Cc: julien.grall@xxxxxxxxxx, paolo.valente@xxxxxxxxxx, keir@xxxxxxx, stefano.stabellini@xxxxxxxxxxxxx, tim@xxxxxxx, dario.faggioli@xxxxxxxxxx, Ian.Jackson@xxxxxxxxxxxxx, Ian.Campbell@xxxxxxxxxxxxx, etrudeau@xxxxxxxxxxxx, JBeulich@xxxxxxxx, viktor.kleinik@xxxxxxxxxxxxxxx
- Delivery-date: Tue, 22 Apr 2014 19:35:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
Hi Arianna,
On 21/04/14 14:44, Arianna Avanzini wrote:
---
xen/arch/arm/p2m.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 403fd89..7f03aa7 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -319,6 +319,7 @@ static int apply_p2m_changes(struct domain *d,
if ( !populate )
{
addr = (addr + FIRST_SIZE) & FIRST_MASK;
+ maddr = (maddr + FIRST_SIZE) & FIRST_MASK;
We differ a bit from x86 on this point. We will silently ignore that the
GFN is not mapped when op == REMOVE.
I'm wondering if we should return an error in this case. I don't find
any place where it's valid to remove non-present mapping.
[..]
@@ -406,12 +408,26 @@ static int apply_p2m_changes(struct domain *d,
{
pte = mfn_to_p2m_entry(maddr >> PAGE_SHIFT, mattr, t);
write_pte(&third[third_table_offset(addr)], pte);
- maddr += PAGE_SIZE;
}
break;
- case RELINQUISH:
case REMOVE:
{
+ unsigned long mfn = pte.p2m.base;
+
+ /*
+ * Ensure that the guest address given as argument to
+ * this function is actually mapped to the specified
+ * machine address. maddr here is the machine address
+ * given to the function, while mfn is the machine
+ * frame number actually mapped to the guest address:
+ * check if the two correspond.
+ */
+ if ( !pte.p2m.valid || maddr != pfn_to_paddr(mfn) )
+ return -EINVAL;
+ }
+ /* fall through */
+ case RELINQUISH:
+ {
if ( !pte.p2m.valid )
{
count++;
@@ -425,7 +441,6 @@ static int apply_p2m_changes(struct domain *d,
count++;
}
break;
-
Spurious change here.
Regards
--
Julien Grall
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