Eric Blake wrote:
> According to Jim Meyering on 3/1/2010 1:21 PM:
>> Clang warned about the potential NULL-dereference
>> via the STREQ/strcmp below. models[i] could be NULL.
>> Even "models" could be NULL, and the "allowed = ..." test
>> makes that appear to be deliberately allowed.
>
> This same function was also listed by coverity, but only for models, not
> models[i].
Yes, I was disappointed to see Coverity missed that.
>> The change below is the least invasive and cleanest
>> I could come up with, assuming there is no need to diagnose
>> (e.g., by returning -1) the condition of a NULL models[i] pointer.
>>
>> while (candidate != NULL) {
>> bool allowed = (models == NULL);
>>
>> for (i = 0; i < candidate->ncpuid; i++) {
>> cpuid = x86DataCpuid(data, candidate->cpuid[i].function);
>> if (cpuid == NULL
>> || !x86cpuidMatchMasked(cpuid, candidate->cpuid + i))
>> goto next;
>> }
>>
>> for (i = 0; i < nmodels; i++) {
>> - if (STREQ(models[i], candidate->name)) {
>> + if (models && models[i] && STREQ(models[i], candidate->name)) {
>
> Isn't the intent that (models==NULL) iff (nmodels==0)?
That is the intent, but the code at this level does not detect the mismatch.
I think someone made a change recently to protect us at a higher
(cpu-independent) level.
But that doesn't help us here, if a new caller of this function
violates those higher-level constraints.
> In which case,
> this code is unreachable if models is NULL. But your patch certainly is
> the least-invasive possible, and while it is only a false positive for
> well-formed arguments, I didn't spend time checking all clients of
> x86Decode to see if there is ever a possibility of bad arguments.
>
> ACK
Thanks.
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