Sean Anderson wrote: > On 9/10/24 13:42, Willem de Bruijn wrote: > > Sean Anderson wrote: > >> On 9/9/24 21:01, Willem de Bruijn wrote: > >> > Jakub Kicinski wrote: > >> >> On Mon, 09 Sep 2024 13:26:42 -0400 Willem de Bruijn wrote: > >> >> > > This seems to be a bug in the driver. > >> >> > > > >> >> > > A call to skb_put_padto(skb, ETH_ZLEN) should be added. > >> >> > > >> >> > In which case this test detecting it may be nice to have, for lack of > >> >> > a more targeted test. > >> >> > >> >> IIUC we're basically saying that we don't need to trim because pad > >> >> should be 0? In that case maybe let's keep the patch but add a check > >> >> on top which scans the pad for non-zero bytes, and print an informative > >> >> warning? > >> > > >> > Data arriving with padding probably deserves a separate test. > >> > > >> > We can use this csum test as stand-in, I suppose. > >> > > >> > Is it safe to assume that all padding is wrong on ingress, not just > >> > non-zero padding. The ip stack itself treats it as benign and trims > >> > the trailing bytes silently. > >> > > >> > I do know of legitimate cases of trailer data lifting along. > >> > >> Ideally we would test that > >> > >> - Ingress padding is ignored. > > > > I think the goal of a hardware padding test is to detect when padding > > leaks onto the wire. > > Which is the subject of my second bullet. > > > If not adding a new test, detect in csum and fail anytime padding is > > detected (i.e., not only non-zero)? > > As noted below, this is only a problem if we leak kernel memory in the > padding. Otherwise, any kind of padding at all is completely standard > conformant. Ack. I actually was not clear on that.
