[libvirt] [PATCH 6/6] domain_conf: Avoid false positive

[Peter Krempa]

On Tue, May 31, 2016 at 12:55:06 +0200, Peter Krempa wrote:
> On Tue, May 31, 2016 at 12:33:33 +0200, Michal Privoznik wrote:
> > Gcc fails to see that virDomainChrGetDomainPtrsInternal always
> > sets pointers to a non NULL value (except for
> > chr device type VIR_DOMAIN_CHR_DEVICE_TYPE_LAST which if occurs,
> > we are in way bigger problem than NULL deref).
> > 
> > In file included from conf/domain_conf.c:37:0:
> > conf/domain_conf.c: In function 'virDomainChrPreAlloc':
> > conf/domain_conf.c:14109:35: error: potential null pointer dereference [-Werror=null-dereference]
> >      return VIR_REALLOC_N(*arrPtr, *cntPtr + 1);
> >                                    ^~
> > ./util/viralloc.h:158:73: note: in definition of macro 'VIR_REALLOC_N'
> >  # define VIR_REALLOC_N(ptr, count) virReallocN(&(ptr), sizeof(*(ptr)), (count), \
> >                                                                          ^~~~~
> > conf/domain_conf.c: In function 'virDomainChrRemove':
> > conf/domain_conf.c:14133:21: error: potential null pointer dereference [-Werror=null-dereference]
> >      for (i = 0; i < *cntPtr; i++) {
> >                      ^~~~~~~
> > cc1: all warnings being treated as errors
> > 
> > Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> > ---
> >  src/conf/domain_conf.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> > index 3daeb1e..67ed4d7 100644
> > --- a/src/conf/domain_conf.c
> > +++ b/src/conf/domain_conf.c
> > @@ -14106,6 +14106,12 @@ virDomainChrPreAlloc(virDomainDefPtr vmdef,
> >  
> >      virDomainChrGetDomainPtrsInternal(vmdef, chr->deviceType, &arrPtr, &cntPtr);
> >  
> > +    if (!arrPtr || !cntPtr) {
> > +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> > +                       _("Impossible happened"));
> > +        return -1;
> > +    }
> > +
> >      return VIR_REALLOC_N(*arrPtr, *cntPtr + 1);
> >  }
> 
> NACK

virDomainChrGetDomainPtrsInternal can be made to return failure if the
type is invalid rather than open-coding this multiple times.

Additionally the error message is weird.
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