Messages in this thread | | | From | Bartosz Golaszewski <> | Date | Tue, 23 Jun 2020 11:12:24 +0200 | Subject | Re: [PATCH 03/11] net: devres: relax devm_register_netdev() |
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wt., 23 cze 2020 o 00:49 Jakub Kicinski <kuba@kernel.org> napisał(a): > > On Mon, 22 Jun 2020 12:00:48 +0200 Bartosz Golaszewski wrote: > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com> > > > > 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@baylibre.com> > > 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), 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.
> 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.
Bartosz
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