[libvirt] [PATCH v2] fix error when parsing ppc64 models on x86 host

[Eric Blake]

On 12/09/2011 09:45 AM, Stefan Berger wrote:
> When parsing ppc64 models on an x86 host an out-of-memory error message
> is displayed due
> to it checking for retcpus being NULL. Fix this by removing the check
> whether retcpus is NULL
> since we will realloc into this variable.
> Also in the X86 model parser display the OOM error at the location where
> it happens.
> 
> ---
> 
> v2: Fixing leak of 'cpus'

> +    int i, ret;

Uninitialized,

> 
>      do {
>          const char *t;

        if ((next = strchr(p, '\n')))
            next++;

        if (!STRPREFIX(p, "PowerPC "))
            continue;

and you can set p = NULL and get to the continue on the first iteration,

> @@ -523,32 +522,38 @@ qemuCapsParsePPCModels(const char *outpu
>          if (retcpus) {
>              unsigned int len;
> 
> -            if (VIR_REALLOC_N(cpus, count + 1) < 0)
> +            if (VIR_REALLOC_N(cpus, count + 1) < 0) {
>                  virReportOOMError();
> +                ret = -1;
>                  goto error;
> +            }
> 
>              len = t - p - 1;
> 
> -            if (!(cpus[count] = strndup(p, len)))
> +            if (!(cpus[count] = strndup(p, len))) {
>                  virReportOOMError();
> +                ret = -1;
>                  goto error;
> +            }
>          }
>          count++;
>      } while ((p = next));

and then break out of the loop, with ret still unassigned,

> 
>      if (retcount)
>          *retcount = count;
> -    if (retcpus)
> +    if (retcpus) {
>          *retcpus = cpus;
> -    return 0;
> +        cpus = NULL;
> +    }
> +    ret = 0;

but at least you then assign it here, so it is never used unassigned.
It took me a while to follow this logic, but it is correct.

On the other hand, if you initialize ret to -1 where it is declared,
then you don't have to assign it at both virReportOOMError() points, and
you don't have to trace through the entire flow to ensure that you never
reach error: with it unassigned.

> 
>  error:

Also, it might be worth tweaking this to cleanup: instead of error:, now
that we also execute it on success paths.

>      if (cpus) {
>          for (i = 0; i < count; i++)
>              VIR_FREE(cpus[i]);
> +        VIR_FREE(cpus);
>      }
> -    VIR_FREE(cpus);
> -    return -1;
> +    return ret;
>  }
> 
>  int

ACK - what you have is correct, although you might want to squash in my
nits before pushing.  No v3 necessary.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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