linux-kernel - [RFC 01/12] KVM: arm/arm64: Avoid multiple dist->spis kfree

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Date:   Mon, 19 Mar 2018 10:20:09 +0100
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, eric.auger@...hat.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
        cdall@...nel.org, peter.maydell@...aro.org
Cc:     andre.przywara@....com, drjones@...hat.com, wei@...hat.com
Subject: [RFC 01/12] KVM: arm/arm64: Avoid multiple dist->spis kfree

in case kvm_vgic_map_resources() fails, typically if the vgic
distributor is not defined, __kvm_vgic_destroy will be called
several times. Indeed kvm_vgic_map_resources() is called on
first vcpu run. As a result dist->spis is freeed twice and on
the second time it causes a "kernel BUG at mm/slub.c:3912!"

This patch avoids freeing dist->spis twice.

Signed-off-by: Eric Auger <eric.auger@...hat.com>
---
 virt/kvm/arm/vgic/vgic-init.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 743ca5c..38fd5f1 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -324,7 +324,10 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)
 	dist->ready = false;
 	dist->initialized = false;
 
-	kfree(dist->spis);
+	if (dist->spis) {
+		kfree(dist->spis);
+		dist->spis = NULL;
+	}
 	dist->nr_spis = 0;
 
 	if (vgic_supports_direct_msis(kvm))
-- 
2.5.5