Messages in this thread | | | Date | Wed, 3 Oct 2012 11:02:07 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH] mm: use %pK for /proc/vmallocinfo |
| |
On Wed, 3 Oct 2012, Kees Cook wrote:
> > So root does echo 0 > /proc/sys/kernel/kptr_restrict first. Again: what > > are you trying to protect? > > Only CAP_SYS_ADMIN can change the setting. This is, for example, for > containers, or other situations where a uid 0 process lacking > CAP_SYS_ADMIN cannot see virtual addresses. It's a very paranoid case, > yes, but it's part of how this feature was designed. Think of it as > supporting the recent uid 0 vs ring 0 boundary. :) >
The intention of /proc/vmallocinfo being S_IRUSR is obviously to only allow root to read this information to begin with, so if root lacks CAP_SYS_ADMIN then it seems the best fix would be to return an empty file on read()? Or give permission to everybody to read it but only return a positive count when they have CAP_SYS_ADMIN?
There's no need to make this so convoluted that you need to have the right combination of uid, kptr_restrict, CAP_SYS_ADMIN, and CAP_SYSLOG to get anything valuable out of this file, though.
| |