On Thu, Apr 25, 2024 at 05:43:33PM -0700, Kees Cook wrote: > On Thu, Apr 25, 2024 at 08:27:05PM -0400, Kent Overstreet wrote: > > On Thu, Apr 25, 2024 at 04:47:18PM -0700, Andrew Morton wrote: > > > On Thu, 25 Apr 2024 15:42:30 -0700 Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > > > > > The concern about leaking image layout could be addressed by sorting the > > > > > output before returning to userspace. > > > > > > > > It's trivial to change permissions from the default 0400 at boot time. > > > > It can even have groups and ownership changed, etc. This is why we have > > > > per-mount-namespace /proc instances: > > > > > > > > # chgrp sysmonitor /proc/allocinfo > > > > # chmod 0440 /proc/allocinfo > > > > > > > > Poof, instant role-based access control. :) > > > > > > Conversely, the paranoid could set it to 0400 at boot also. > > > > > > > I'm just trying to make the _default_ safe. > > > > > > Agree with this. > > > > > > Semi-seriously, how about we set the permissions to 0000 and force > > > distributors/users to make a decision. > > > > I'm ok with 0400 for now since it's consistent with slabinfo, but I'd > > really like to see a sysctl for debug info paranoia. We shouldn't be > > leaving this to the distros; we're the ones with the expertise to say > > what would be covered by that sysctl. > > We've not had great luck with sysctls (see userns sysctl discussions) > since they don't provide sufficient granularity. > > All this said, I'm still not excited about any of these files living > in /proc at all -- we were supposed to use /sys for this kind of thing, > but its interface wasn't great for this kind of more "free-form" data, > and debugfs isn't good for production interfaces. /proc really should > only have pid information -- we end up exposing these top-level files to > every mount namespace with a /proc mount. :( But that's a yet-to-be-solved > problem... It really wouldn't be that hard to relax the 4k file limit in sysfs.
