Am 20.02.2014 14:07, schrieb Paolo Bonzini:
> Il 20/02/2014 13:34, Dan Carpenter ha scritto:
>> This seems like a harmless off by one overflow if "i" is the last
>> element in the vcpu->arch.cpuid_entries[] array.
>>
>> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>> ---
>> Not tested. I always wonder if it's worth fixing these or if it's worth
>> reporting them? Either of those seem like a lot of work for something
>> harmless.
>
> Could it oops if cpuid_nent is INT_MAX? If so, it's not entirely harmless.
> In this case I'd rather take the occasion to cleanup the code like this
> (compile-tested):
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 9fed5bedaad6..2fd6e7169936 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -656,18 +656,19 @@ out:
> static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)
> {
> struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
> - int j, nent = vcpu->arch.cpuid_nent;
> + struct kvm_cpuid_entry2 *ej;
> + int j = i, nent = vcpu->arch.cpuid_nent;
>
> e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
> +
> /* when no next entry is found, the current entry[i] is reselected */
> - for (j = i + 1; ; j = (j + 1) % nent) {
> - struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
> - if (ej->function == e->function) {
> - ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
> - return j;
> - }
> - }
> - return 0; /* silence gcc, even though control never reaches here */
> + do {
> + j = (j + 1) % nent;
> + ej = &vcpu->arch.cpuid_entries[j];
> + } while (ej->function != e->function);
> +
> + ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
> + return j;
> }
>
> /* find an entry with matching function, matching index (if needed), and that
>
> What do you think?
>
Is there any guaranty that this will not loop forever ?
an if (i==j) return 0; would be on the save side. (I guess that
these was the idea behind the for).
re,
wh
> Paolo
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