On Tue, 23 Jun 2020 11:12:24 +0200 Bartosz Golaszewski wrote: > wt., 23 cze 2020 o 00:49 Jakub Kicinski <kuba@xxxxxxxxxx> napisał(a): > > On Mon, 22 Jun 2020 12:00:48 +0200 Bartosz Golaszewski wrote: > > > From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> > > > > > > This devres helper registers a release callback that only unregisters > > > the net_device. It works perfectly fine with netdev structs that are > > > not managed on their own. There's no reason to check this - drop the > > > warning. > > > > > > Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> > > > > I think the reasoning for this suggestion was to catch possible UAF > > errors. The netdev doesn't necessarily has to be from devm_alloc_* > > but it has to be part of devm-ed memory or memory which is freed > > after driver's remove callback. > > > > Yes I understand that UAF was the concern here, but this limitation is > unnecessary. In its current form devm_register_netdev() only works for > struct net_device allocated with devm_alloc_etherdev(). Meanwhile > calling alloc_netdev() (which doesn't have its devm counterpart yet - > I may look into it shortly), If resource managed alloc_netdev() is needed devm_alloc_netdev() can be created, and even reuse devm_free_netdev() so no changes to the warning are even necessary for such extension. > then registering a devm action with devm_add_action_or_reset() which > would free this memory is a perfectly fine use case. This patch would > make it possible. alloc_netdev() + devm_add_action makes no sense in the upstream kernel, just add the appropriate helper, we care little about out of tree code. > > Are there cases in practice where you've seen the netdev not being > > devm allocated? > > As I said above - alloc_netdev() used by wireless, can, usb etc. > drivers doesn't have a devres variant.
