linux-kernel - [PATCH v2 2/2] KVM: PPC: Book3S HV: XIVE: Fix potential page leak on error path

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Date:   Wed, 13 Nov 2019 17:46:19 +0100
From:   Greg Kurz <groug@...d.org>
To:     Paul Mackerras <paulus@...abs.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Cédric Le Goater <clg@...d.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Lijun Pan <ljp@...ux.ibm.com>,
        Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>,
        Laurent Vivier <lvivier@...hat.com>, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] KVM: PPC: Book3S HV: XIVE: Fix potential page leak
 on error path

We need to check the host page size is big enough to accomodate the
EQ. Let's do this before taking a reference on the EQ page to avoid
a potential leak if the check fails.

Cc: stable@...r.kernel.org # v5.2
Fixes: 13ce3297c576 ("KVM: PPC: Book3S HV: XIVE: Add controls for the EQ configuration")
Signed-off-by: Greg Kurz <groug@...d.org>
---
 arch/powerpc/kvm/book3s_xive_native.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
index 0e1fc5a16729..d83adb1e1490 100644
--- a/arch/powerpc/kvm/book3s_xive_native.c
+++ b/arch/powerpc/kvm/book3s_xive_native.c
@@ -630,12 +630,6 @@ static int kvmppc_xive_native_set_queue_config(struct kvmppc_xive *xive,
 
 	srcu_idx = srcu_read_lock(&kvm->srcu);
 	gfn = gpa_to_gfn(kvm_eq.qaddr);
-	page = gfn_to_page(kvm, gfn);
-	if (is_error_page(page)) {
-		srcu_read_unlock(&kvm->srcu, srcu_idx);
-		pr_err("Couldn't get queue page %llx!\n", kvm_eq.qaddr);
-		return -EINVAL;
-	}
 
 	page_size = kvm_host_page_size(kvm, gfn);
 	if (1ull << kvm_eq.qshift > page_size) {
@@ -644,6 +638,13 @@ static int kvmppc_xive_native_set_queue_config(struct kvmppc_xive *xive,
 		return -EINVAL;
 	}
 
+	page = gfn_to_page(kvm, gfn);
+	if (is_error_page(page)) {
+		srcu_read_unlock(&kvm->srcu, srcu_idx);
+		pr_err("Couldn't get queue page %llx!\n", kvm_eq.qaddr);
+		return -EINVAL;
+	}
+
 	qaddr = page_to_virt(page) + (kvm_eq.qaddr & ~PAGE_MASK);
 	srcu_read_unlock(&kvm->srcu, srcu_idx);