On Wed, Oct 29, 2014 at 11:50:12AM -0700, Junio C Hamano wrote: > Jeff King <peff@xxxxxxxx> writes: > > > I'm a little iffy on this just because it is fixing one particular bug, > > and I am sure there are probably a bunch of other ways to have a bogus > > index. Fundamentally, I think we pretty much trust that the index was > > not maliciously generated (unlike packfiles, for instance, which can > > come from elsewhere). Still, this is one step closer to safe, and the > > bug was seen in the wild, so maybe it is worth doing. > > Is it cheap to sanity-check the input when we map in the cache-tree > upon read_cache()? Then we can just invalidate the cache-tree, > either in its entirety (easy) or just the bogus subpart (maybe not > worth doing). I think it is not super-expensive, but it is not as easy as: if (!it->entry_count) return -1; > > We could alternatively (or in addition) reject 0-entry cache trees when > > reading them from disk. The trick, though, is that it is not just > > records with 0 entries, but ones where the sum of the entries and > > subtree entries is 0. Given that it is not something we expect to > > happen, it is easier to catch it here. And we know there can be no > > regressions for missed corner cases, because the case we are catching > > here would _always_ have gone into an infinite loop before this patch. > > OK. I wonder if we can instead die here but propagate the error > back up the callchain and have the ultimate caller rebuild the cache > tree without paying attention to the existing data that we now know > is bogus. Yeah, that would make sense to me, but I was not familiar with the cache-tree code to do it easily (and given that this is not something that should ever happen, I didn't want to spend time digging in). I can provide you with a real-world test case if you want to explore it further. -Peff -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html