Re: [libvirt] [PATCH 02/17] nwfilter: Fix possible corruption on failure path during LoadConfig

On 07/13/2017 10:41 AM, Michal Privoznik wrote: > On 06/02/2017 12:25 PM, John Ferlan wrote: >> If the virNWFilterSaveConfig in virNWFilterObjListLoadConfig, then jumping > > s/,/ fails,/ > >> to the error label would free the @def owned by the object, but the object >> is still on the list. >> >> Fix this by following proper procedure to clear @def and create a new >> variable @objdef to handle the object's def after successful assignment. >> >> Signed-off-by: John Ferlan <jferlan(a)redhat.com&gt; >> --- >> src/conf/virnwfilterobj.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/src/conf/virnwfilterobj.c b/src/conf/virnwfilterobj.c >> index 0027d45..3fb6046 100644 >> --- a/src/conf/virnwfilterobj.c >> +++ b/src/conf/virnwfilterobj.c >> @@ -485,6 +485,7 @@ virNWFilterObjListLoadConfig(virNWFilterObjListPtr nwfilters, >> { >> virNWFilterDefPtr def = NULL; >> virNWFilterObjPtr obj; >> + virNWFilterDefPtr objdef; >> char *configFile = NULL; >> >> if (!(configFile = virFileBuildPath(configDir, name, ".xml"))) >> @@ -503,10 +504,12 @@ virNWFilterObjListLoadConfig(virNWFilterObjListPtr nwfilters, >> >> if (!(obj = virNWFilterObjListAssignDef(nwfilters, def))) >> goto error; >> + def = NULL; >> + objdef = obj->def; >> >> /* We generated a UUID, make it permanent by saving the config to disk */ >> - if (!def->uuid_specified && >> - virNWFilterSaveConfig(configDir, def) < 0) >> + if (!objdef->uuid_specified && >> + virNWFilterSaveConfig(configDir, objdef) < 0) >> goto error; > > This @objdef variable looks redundant to me. Can't we access obj->def > directly? Esp. since you're introducing a variable just for a two times > use. Then again, we often use obj->def->... when it comes to domain > objects, why not here? > If obj->def ever gets "consumed" by the virObject code, then obj->def->x will fail miserably. That was the original design goal. I've since had to scale back. I guess I could do "obj->def->uuid_specified" as it doesn't really matter until the day obj->def-> is no longer accessible. As a preference - I like the extra local variable. In the long run the compiler will do away with it, but for me it just reads better that way. The deeper one gets into a->b->c->d[->e...] the more insane it gets. Forcing one level of indirection is just more readable to me.