linux-kernel - [PATCH v2 13/13] KVM: selftests: Verify that reads to inaccessible guest

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Message-ID: <20251003232606.4070510-14-seanjc@google.com>
Date: Fri,  3 Oct 2025 16:26:06 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	David Hildenbrand <david@...hat.com>, Fuad Tabba <tabba@...gle.com>, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: [PATCH v2 13/13] KVM: selftests: Verify that reads to inaccessible
 guest_memfd VMAs SIGBUS

Expand the guest_memfd negative testcases for overflow and MAP_PRIVATE to
verify that reads to inaccessible memory also get a SIGBUS.

Opportunistically fix the write path to use the "val" instead of hardcoding
the literal value a second time, and to use TEST_FAIL(...) instead of
TEST_ASSERT(false, ...).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index f5372fdf096d..e7d9aeb418d3 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -84,6 +84,7 @@ static void test_fault_sigbus(int fd, size_t accessible_size, size_t map_size)
 	mem = kvm_mmap(map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd);
 
 	TEST_EXPECT_SIGBUS(memset(mem, val, map_size));
+	TEST_EXPECT_SIGBUS((void)READ_ONCE(mem[accessible_size]));
 
 	for (i = 0; i < accessible_size; i++)
 		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);
-- 
2.51.0.618.g983fd99d29-goog