Hi, Thanks for the feedback. This patch results from manual inspection of the code. I agree my commit description is abusive: in the case of bonding, I think everything is fine, there should be no ref leak, cleanup paths seem clean.
My point was to make things more predictable: ndo_netpoll_cleanup called anyways to acknowledge actual loss of a ref to npinfo, irrespective of whether it's the last ref or not. Without this patch, calling ndo_netpoll_cleanup would depend on some timing behavior, hard to predict, and users of the API have better be careful to reclaim the refs manually anyways: as a consequence, not sure this callback is actually required in its current inception. On Mon, Jul 7, 2014 at 7:35 PM, David Miller <[email protected]> wrote: > From: David Decotigny <[email protected]> > Date: Mon, 30 Jun 2014 16:50:10 -0700 > >> This ensures that the ndo_netpoll_cleanup callback is called for every >> device that provides one. Otherwise there is a risk of reference leak >> with bonding for example, which depends on this callback to cleanup >> the slaves' references to netpoll info. >> >> Tested: >> see patch "netpoll: fix use after free" >> >> Signed-off-by: David Decotigny <[email protected]> > > I definitely don't understand this. > > Why would we call the cleanup function of an object before it's > reference count hits zero? It is exactly the act of reaching a > zero refcount which should trigger invoking the cleanup callback. > > If a refcount is being released in another location without checking > if it hits zero and invoking the cleanup if so, _THAT_ is the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
