On Mon, Dec 24, 2018 at 12:45:59PM +0100, Greg KH wrote: > On Mon, Dec 24, 2018 at 12:09:37PM +0100, Christian Brauner wrote: > > On Sun, Dec 23, 2018 at 03:35:49PM +0100, Christian Brauner wrote: > > > Since binderfs can be mounted by userns root in non-initial user namespaces > > > some precautions are in order. First, a way to set a maximum on the number > > > of binder devices that can be allocated per binderfs instance and second, a > > > way to reserve a reasonable chunk of binderfs devices for the initial ipc > > > namespace. > > > A first approach as seen in [1] used sysctls similiar to devpts but was > > > shown to be flawed (cf. [2] and [3]) since some aspects were unneeded. This > > > is an alternative approach which avoids sysctls completely and instead > > > switches to a single mount option. > > > > > > Starting with this commit binderfs instances can be mounted with a limit on > > > the number of binder devices that can be allocated. The max=<count> mount > > > option serves as a per-instance limit. If max=<count> is set then only > > > <count> number of binder devices can be allocated in this binderfs > > > instance. > > > > > > This allows to safely bind-mount binderfs instances into unprivileged user > > > namespaces since userns root in a non-initial user namespace cannot change > > > the mount option as long as it does not own the mount namespace the > > > binderfs mount was created in and hence cannot drain the host of minor > > > device numbers > > > > > > [1]: https://lore.kernel.org/lkml/20181221133909.18794-1-christian@xxxxxxxxxx/ > > > [2]; https://lore.kernel.org/lkml/20181221163316.GA8517@xxxxxxxxx/ > > > [3]: https://lore.kernel.org/lkml/CAHRSSEx+gDVW4fKKK8oZNAir9G5icJLyodO8hykv3O0O1jt2FQ@xxxxxxxxxxxxxx/ > > > [4]: https://lore.kernel.org/lkml/20181221192044.5yvfnuri7gdop4rs@xxxxxxxxxx/ > > > > > > Cc: Todd Kjos <tkjos@xxxxxxxxxx> > > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > > Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx> > > > > Right, I forgot to ask. Do we still have time to land this alongside the > > other patches in 4.21? :) > > It's too late for 4.21-rc1, but let's see what happens after that :) Sweet! Much appreciated. :) Christian _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
