linux-kernel - [PATCH v2 002/144] KVM: selftests: Fix buggy-but-benign check in test_v3_new_redist

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Date:   Fri,  3 Jun 2022 00:41:09 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>,
        Oliver Upton <oupton@...gle.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 002/144] KVM: selftests: Fix buggy-but-benign check in test_v3_new_redist_regions()

Update 'ret' with the return value of _kvm_device_access() prior to
asserting that ret is non-zero.  In the current code base, the flaw is
benign as 'ret' is guaranteed to be -EBUSY from the previous run_vcpu(),
which also means that errno==EBUSY prior to _kvm_device_access(), thus
the "errno == EFAULT" part of the assert means that a false negative is
impossible (unless the kernel is being truly mean and spuriously setting
errno=EFAULT while returning success).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/aarch64/vgic_init.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/aarch64/vgic_init.c b/tools/testing/selftests/kvm/aarch64/vgic_init.c
index 34379c98d2f4..0f046e3e953d 100644
--- a/tools/testing/selftests/kvm/aarch64/vgic_init.c
+++ b/tools/testing/selftests/kvm/aarch64/vgic_init.c
@@ -381,8 +381,8 @@ static void test_v3_new_redist_regions(void)
 	v = vm_gic_create_with_vcpus(KVM_DEV_TYPE_ARM_VGIC_V3, NR_VCPUS);
 	subtest_v3_redist_regions(&v);
 
-	_kvm_device_access(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_ADDR,
-			  KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION, dummy, true);
+	ret = _kvm_device_access(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_ADDR,
+				 KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION, dummy, true);
 	TEST_ASSERT(ret && errno == EFAULT,
 		    "register a third region allowing to cover the 4 vcpus");
 
-- 
2.36.1.255.ge46751e96f-goog