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 <[email protected]> >> --- >> 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 > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
