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: > We already know how big replies can get, so we can perform a complete > sanity check quite early: > > diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c > index a08aeb56b8e4..14f4d425cf8c 100644 > --- a/net/sunrpc/svc.c > +++ b/net/sunrpc/svc.c > @@ -1196,6 +1196,12 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv) > goto err_bad_proc; > rqstp->rq_procinfo = procp; > > + if ((procp->pc_xdrressize == 0 || > + procp->pc_xdrressize > XDR_QUADLEN(PAGE_SIZE)) && > + rqstp->rq_arg.len > PAGE_SIZE) > + /* The assumption about request/reply sizes in svc_init_buffer() is violated! */ > + goto err_garbage; > + > /* Syntactic check complete */ > serv->sv_stats->rpccnt++; > > > I haven't tested this at all and haven't even convinced myself that > it covers every case (though I cannot immediately think of any likely > corners). > > Does it address your test case? I'll check, it probably does. We'd need to limit the test to v2/v3. I'm also not opposed to doing both (or all three). --b. -- 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
