On Mon, Oct 02, 2017 at 07:42:17AM -0700, Eric Dumazet wrote: > On Mon, Oct 2, 2017 at 7:21 AM, Mark Rutland <mark.rutl...@arm.com> wrote: > > Just to check I've understood correctly, are you suggesting that the > > IPv4 code should also check the dev->mtu against a IP_MIN_MTU (which > > doesn't seem to exist today)? > > We have plenty of places this is checked. > > For example, trying to set MTU < 68 usually removes IPv4 addresses and routes. > > Problem is : these checks are not fool proof yet. > > ( Only the admin was supposed to play these games )
Sorry, I meant that there was no constant called IP_MIN_MTU, and I was just looking at the sites fixed up by c780a049f9bf4423. I appreciate given that this requires admin privileges it's not exactly high priority. I didn't mean for the above to sound like some kind of accusation! > > Otherwise, I do spot another potential issue. The writer side (e.g. most > > net_device::ndo_change_mtu implementations and the __dev_set_mtu() > > fallback) doesn't use WRITE_ONCE(). > > It does not matter how many strange values can be observed by the reader : > We must be fool proof anyway from reader point of view, so the > WRITE_ONCE() is not strictly needed. Ok. If we expect to always check somewhere on the reader side I guess that makes sense. Thanks, Mark.
