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Re: [libvirt] [PATCH] daemon: Fix crash in virTypedParameterArrayClear



On Mon, Jul 30, 2012 at 21:08:22 +0800, Osier Yang wrote:
> On 2012年07月30日 19:55, Jiri Denemark wrote:
> > Daemon uses the following pattern when dispatching APIs with typed
> > parameters:
> >
> >      VIR_ALLOC_N(params, nparams);
> >      virDomain*(dom, params,&nparams, flags);
> >      virTypedParameterArrayClear(params, nparams);
> >
> > In case nparams was originally set to 0, virDomain* API would fill it
> > with the number of typed parameters it can provide and we would use this
> > number (rather than zero) to clear params. Because VIR_ALLOC* returns
> > non-NULL pointer even if size is 0, the code would end up walking
> > through random memory. If we were lucky enough and the memory contained
> > 7 (VIR_TYPED_PARAM_STRING) at the right place, we would try to free a
> > random pointer and crash.
> >
> > Let's make sure params stays NULL when nparams is 0.
> > ---
> >   daemon/remote.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/daemon/remote.c b/daemon/remote.c
> > index 80626a2..d25717c 100644
> > --- a/daemon/remote.c
> > +++ b/daemon/remote.c
> > @@ -989,7 +989,7 @@ remoteDispatchDomainGetSchedulerParameters(virNetServerPtr server ATTRIBUTE_UNUS
> >           virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
> >           goto cleanup;
> >       }
> > -    if (VIR_ALLOC_N(params, nparams)<  0)
> > +    if (nparams&&  VIR_ALLOC_N(params, nparams)<  0)
> >           goto no_memory;
> >
> >       if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
> > @@ -1098,7 +1098,7 @@ remoteDispatchDomainGetSchedulerParametersFlags(virNetServerPtr server ATTRIBUTE
> >           virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
> >           goto cleanup;
> >       }
> > -    if (VIR_ALLOC_N(params, nparams)<  0)
> > +    if (nparams&&  VIR_ALLOC_N(params, nparams)<  0)
> 
> Isn't nparams for these 2 APIs are guarantee positive in the APIs?
> 
> virCheckPositiveArgGoto(*nparams, error);

Yes but this function is an entry point from RPC and the daemon should not
rely on client-side checking.

Jirka


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