On Fri, Jan 24, 2020 at 13:40:03 +0100, Michal Privoznik wrote: > Since v5.6.0-48-g270583ed98 we try to cache domain capabilities, > i.e. store filled virDomainCaps in a hash table in virQEMUCaps > for future use. However, there's a race condition in the way it's > implemented. We use virQEMUCapsGetDomainCapsCache() to obtain the > pointer to the hash table, then we search the hash table for > cached data and if none is found the domcaps is constructed and > put into the table. Problem is that this is all done without any > locking, so if there are two threads trying to do the same, one > will succeed and the other will fail inserting the data into the > table. > > Also, the API looks a bit fishy - obtaining pointer to the hash > table is dangerous. > > The solution is to use a mutex that guards the whole operation > with the hash table. Then, the API can be changes to return > virDomainCapsPtr directly. > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1791790 > > Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx> > --- > > diff to v1: > - Dropped the callback in favor of passing necessary values as arguments Reviewed-by: Peter Krempa <pkrempa@xxxxxxxxxx>
