On Wed, Jan 19, 2022 at 05:24:23PM +0100, Christian Brauner wrote: > On Wed, Jan 19, 2022 at 06:48:03PM +0300, Alexey Dobriyan wrote: > > From 61376c85daab50afb343ce50b5a97e562bc1c8d3 Mon Sep 17 00:00:00 2001 > > From: Alexey Dobriyan <adobriyan@xxxxxxxxx> > > Date: Mon, 22 Nov 2021 20:41:06 +0300 > > Subject: [PATCH 1/1] proc: "mount -o lookup=..." support > > > > Docker implements MaskedPaths configuration option > > > > https://github.com/estesp/docker/blob/9c15e82f19b0ad3c5fe8617a8ec2dddc6639f40a/oci/defaults.go#L97 > > > > to disable certain /proc files. It overmounts them with /dev/null. > > > > Implement proper mount option which selectively disables lookup/readdir > > in the top level /proc directory so that MaskedPaths doesn't need > > to be updated as time goes on. > > I might've missed this when this was sent the last time so maybe it was > clearly explained in an earlier thread: What's the reason this needs to > live in the kernel? The reasons are: MaskedPaths or equivalents are blacklists, not future proof MaskedPaths is applied at container creation once, lookup= is applied at mount time surely but names aren't required to exist to be filtered (read: some silly ISV module gets loaded, creates /proc entries, containers get them with all security holes) > The MaskedPaths entry is optional so runtimes aren't required to block > anything by default and this mostly makes sense for workloads that run > privileged. > > In addition MaskedPaths is a generic option which allows to hide any > existing path, not just proc. Even in the very docker-specific defaults > /sys/firmware is covered. Sure, the patch is for /proc only. MaskedPaths can't overmount with /dev/null file which doesn't exist yet. > I do see clear value in the subset= and hidepid= options. They are > generally useful independent of opinionated container workloads. I don't > see the same for lookup=. > > An alternative I find more sensible is to add a new value for subset= > that hides anything(?) that only global root should have read/write > access too.
