On Fri, Apr 21, 2017 at 08:11:59AM +1000, NeilBrown wrote: > On Thu, Apr 20 2017, J. Bruce Fields wrote: > > > On Thu, Apr 20, 2017 at 12:19:35PM -0400, J. Bruce Fields wrote: > >> On Tue, Apr 18, 2017 at 01:13:51PM -0400, J. Bruce Fields wrote: > >> > On Tue, Apr 18, 2017 at 10:25:20AM +1000, NeilBrown wrote: > >> > > I can't say that I like this patch at all. > >> > > > >> > > The problem is that: > >> > > > >> > > pages = size / PAGE_SIZE + 1; /* extra page as we hold both request and reply. > >> > > * We assume one is at most one page > >> > > */ > >> > > > >> > > this assumption is never verified. > >> > > To my mind, the "obvious" way to verify this assumption is that an > >> > > attempt to generate a multi-page reply should fail if there was a > >> > > multi-page request. > >> > > >> > A third option, by the way, which Ari Kauppi argued for, is adding a > >> > null check each time we increment rq_next_page, since we seem to arrange > >> > for the page array to always be NULL-terminated. > >> > > >> > > Failing if there was a little bit of extra noise at the end of the > >> > > request seems harsher than necessary, and could result in a regression. > >> > > >> > You're worrying there might be a weird old client out there somewhere? > >> > I guess it seems like a small enough risk to me. I'm more worried the > >> > extra garbage might violate assumptions elsewhere in the code. > >> > > >> > But, this looks good too: > >> > >> But, I'm not too happy about putting that NFSv2/v3-specific check in > >> common rpc code. Also, I think this check comes too late for some of > >> the damage. > > Too late? It is earlier than anything else. D'oh, yes, I had some idea the check happened after encoding. > >> I may go with some variation on Ari's idea, let me give it a try.... > > > > In the read case, I think Ari's approach wouldn't catch the error until > > nfsd_direct_splice_actor(), which doesn't actually look capable of > > handling errors. Maybe that should be fixed. Or maybe read just needs > > some more checks. Ugh. > > By the time you get to nfsd_read(), the 'struct kvec' should be set up > and valid. That's ignored in the splice case, isn't it? OK, maybe I need to sleep on it and look again in the morning.... --b. > So we need checks is e.g. nfs3svc_decode_readargs(), but not > deeper. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
