linux-kernel - Re: [PATCH 01/11] KVM: selftests: Fix out-of-bounds reads in CPUID test's array lookups

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Message-ID: <874j5sjmzz.fsf@redhat.com>
Date: Fri, 04 Oct 2024 10:22:40 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] KVM: selftests: Fix out-of-bounds reads in CPUID
 test's array lookups

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

> When looking for a "mangled", i.e. dynamic, CPUID entry, terminate the
> walk based on the number of array _entries_, not the size in bytes of
> the array.  Iterating based on the total size of the array can result in
> false passes, e.g. if the random data beyond the array happens to match
> a CPUID entry's function and index.
>
> Fixes: fb18d053b7f8 ("selftest: kvm: x86: test KVM_GET_CPUID2 and guest visible CPUIDs against KVM_GET_SUPPORTED_CPUID")
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  tools/testing/selftests/kvm/x86_64/cpuid_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/cpuid_test.c b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
> index 8c579ce714e9..fec03b11b059 100644
> --- a/tools/testing/selftests/kvm/x86_64/cpuid_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
> @@ -60,7 +60,7 @@ static bool is_cpuid_mangled(const struct kvm_cpuid_entry2 *entrie)
>  {
>  	int i;
>  
> -	for (i = 0; i < sizeof(mangled_cpuids); i++) {
> +	for (i = 0; i < ARRAY_SIZE(mangled_cpuids); i++) {
>  		if (mangled_cpuids[i].function == entrie->function &&
>  		    mangled_cpuids[i].index == entrie->index)
>  			return true;

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly