linux-kernel - [PATCH] kvm: warn on more invariant breakage

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Date:	Sun, 28 Dec 2014 10:03:15 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH] kvm: warn on more invariant breakage

Modifying a non-existent slot is not allowed.  Also check that the
first loop doesn't move a deleted slot beyond the used part of
the mslots array.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 virt/kvm/kvm_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 050974c051b5..1cc6e2e19982 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -671,6 +671,7 @@ static void update_memslots(struct kvm_memslots *slots,
 
 	WARN_ON(mslots[i].id != id);
 	if (!new->npages) {
+		WARN_ON(!mslots[i].npages);
 		new->base_gfn = 0;
 		if (mslots[i].npages)
 			slots->used_slots--;
@@ -704,7 +705,8 @@ static void update_memslots(struct kvm_memslots *slots,
 			slots->id_to_index[mslots[i].id] = i;
 			i--;
 		}
-	}
+	} else
+		WARN_ON_ONCE(i != slots->used_slots);
 
 	mslots[i] = *new;
 	slots->id_to_index[mslots[i].id] = i;
-- 
1.8.3.1

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