On Mon, 2012-01-30 at 16:38 -0600, Will Drewry wrote: > On Mon, Jan 30, 2012 at 4:18 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Mon, 2012-01-30 at 16:58 -0500, Colin Walters wrote: > >> On Mon, 2012-01-30 at 08:17 -0800, Andy Lutomirski wrote: > >> > Chroot can easily be used to subvert setuid programs. If no_new_privs, > >> > then setuid programs don't gain any privilege, so allow chroot. > >> > >> Is this needed/desired by anyone now, or are you just using it to "demo" > >> NO_NEW_PRIVS? I don't see it as very useful on its own, since in any > >> "container"-type chroot you really want /proc and /dev, and your patch > >> doesn't help with that. > >> > >> System daemons that do chroot for a modicum of security already start > >> privileged, so this doesn't help them either. > > > > I thought this was all for sandboxing? If a browers (or user) wants to > > run some untrusted code, perhaps a chroot is the best way to do so. It > > just will break if it needs to access /proc or /dev. I think you'll find your definition of "code" becomes very limited without /dev/null, /dev/zero and /proc/cpuinfo for example, as used by glibc. Personally I find it amazing we're even debating putting new security-relevant API in the kernel with no known userspace consumer. It can always go in later if someone actually wants it. > Interestingly, I believe this change would work for the Chromium > setuid sandbox[1]. It uses a fancy clone trick (CLONE_FS) to start the > process then chroot once all its dependencies are loaded. It then > chroot()s to /proc/self/fd_info (or another empty process-specific > directory). But...it's setuid, so it can call chroot already? I'm not following how this change would benefit the helper. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
