linux-kernel - [ 013/221] KVM: Fix user memslot overlap check

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Date:	Tue, 15 Jan 2013 10:49:00 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk,
	Alex Williamson <alex.williamson@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: [ 013/221] KVM: Fix user memslot overlap check

3.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alex Williamson <alex.williamson@...hat.com>

commit 5419369ed6bd4cf711fdda5e52a5999b940413f5 upstream.

Prior to memory slot sorting this loop compared all of the user memory
slots for overlap with new entries.  With memory slot sorting, we're
just checking some number of entries in the array that may or may not
be user slots.  Instead, walk all the slots with kvm_for_each_memslot,
which has the added benefit of terminating early when we hit the first
empty slot, and skip comparison to private slots.

Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 virt/kvm/kvm_main.c |   13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -709,8 +709,7 @@ int __kvm_set_memory_region(struct kvm *
 	int r;
 	gfn_t base_gfn;
 	unsigned long npages;
-	unsigned long i;
-	struct kvm_memory_slot *memslot;
+	struct kvm_memory_slot *memslot, *slot;
 	struct kvm_memory_slot old, new;
 	struct kvm_memslots *slots, *old_memslots;
 
@@ -761,13 +760,11 @@ int __kvm_set_memory_region(struct kvm *
 
 	/* Check for overlaps */
 	r = -EEXIST;
-	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
-		struct kvm_memory_slot *s = &kvm->memslots->memslots[i];
-
-		if (s == memslot || !s->npages)
+	kvm_for_each_memslot(slot, kvm->memslots) {
+		if (slot->id >= KVM_MEMORY_SLOTS || slot == memslot)
 			continue;
-		if (!((base_gfn + npages <= s->base_gfn) ||
-		      (base_gfn >= s->base_gfn + s->npages)))
+		if (!((base_gfn + npages <= slot->base_gfn) ||
+		      (base_gfn >= slot->base_gfn + slot->npages)))
 			goto out_free;
 	}
 


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