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

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Message-ID: <diqz5xcrgaa5.fsf@google.com>
Date: Mon, 06 Oct 2025 11:22:42 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.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>
Subject: Re: [PATCH v2 13/13] KVM: selftests: Verify that reads to
 inaccessible guest_memfd VMAs SIGBUS

Sean Christopherson <seanjc@...gle.com> writes:

> 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, ...).
>

The change the use "val" isn't in this patch, and I think the
TEST_FAIL() change was intended for another earlier patch.

Reviewed-by: Ackerley Tng <ackerleytng@...gle.com>
Tested-by: Ackerley Tng <ackerleytng@...gle.com>

> 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