Re: [Xen-devel] [PATCH] libxc/pm: Fix NULL pointer checks.

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Andrew Cooper writes ("[PATCH] libxc/pm: Fix NULL pointer checks."):
> Discovered by Coverity,
> CIDs 1054968 1054969 1054970 1054971 1054972 1054973 10549704
> 
> This was broken by c/s 5cc436c1d2b3b0 which did a blanket change of 'int
> xc_handle' -> 'xc_interface *xch'.  The types got updated, but error
> conditions were left as-were.  (I suspect some sed was involved originally)

I see this has been committed, but I feel moved to comment:

...
> diff --git a/tools/libxc/xc_pm.c b/tools/libxc/xc_pm.c
> index fa9b246..ea1e251 100644
> --- a/tools/libxc/xc_pm.c
> +++ b/tools/libxc/xc_pm.c
> @@ -285,7 +285,7 @@ int xc_set_cpufreq_gov(xc_interface *xch, int cpuid, char 
> *govname)
>      DECLARE_SYSCTL;
>      char *scaling_governor = sysctl.u.pm_op.u.set_gov.scaling_governor;
>  
> -    if ( (xch < 0) || (!govname) )
> +    if ( !xch || !govname )
>          return -EINVAL;

TBH I think callers who pass null xch's into xc should get a null
pointer dereference, not EINVAL.

But I don't propose to try to go through libxc and drain its crazy
error handling swamp.

Ian.

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