On Fri, Sep 12, 2025 at 05:54:16PM +0300, Laurent Pinchart wrote: > On Fri, Sep 12, 2025 at 04:44:56PM +0200, Bartosz Golaszewski wrote: > > On Fri, Sep 12, 2025 at 4:40 PM Greg Kroah-Hartman > > <gre...@linuxfoundation.org> wrote: > > > > > > Dan's proposal here is a good start, but the "sleep in cdev_del() until > > > the device drains all existing opens" is going to not really work well > > > for what we want. > > > > > > So sure, make a new cdev api to use this, that's fine, then we will have > > > what, 5 different ways to use a cdev? :) > > > > > > Seriously, that would be good, then we can work to convert things over, > > > but I think overall it will look much the same as what patch 5/5 does > > > here. But details matter, I don't really known for sure... > > > > > > Either way, I think this patch series stands on its own, it doesn't > > > require cdev to implement it, drivers can use it to wrap a cdev if they > > > want to. We have other structures that want to do this type of thing > > > today as is proof with the rust implementation for the devm api. > > > > Yeah, I'm not against this going upstream. If more development is > > needed for this to be usable in other parts of the kernel, that can be > > done gradually. Literally no subsystem ever was perfect on day 1. > > To be clear, I'm not against the API being merged for the use cases that > would benefit from it, but I don't want to see drivers using it to > protect from the cdev/unregistration race.
Based on the discussion thread, my main takeaways are: - Current `revocable` is considered a low level API. We shouldn't (and likely can't) stop drivers, like the one in patch 5/5 in the series, from using it directly to fix UAFs. - Subsystems (like cdev) should build on this API to provide an easier interface for their drivers to manage revocable resources. I'll create a PoC based on this. > > Tzung-Bi: I'm not sure if you did submit anything but I'd love to see > > this discussed during Linux Plumbers in Tokyo, it's the perfect fit > > for the kernel summit. Yes, and I just realized that in addition to the website submission, a separate email is also required (or at least encouraged). I've just sent that email and am hoping it's not too late.
