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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>