|From:||Linus Torvalds <torvalds-AT-linux-foundation.org>|
|To:||Jamie Lokier <jamie-AT-shareable.org>|
|Subject:||Re: [PATCH PLACEHOLDER 1/3] fs/exec: "always_unprivileged" patch|
|Date:||Sat, 14 Jan 2012 12:22:55 -0800|
|Cc:||Andrew Lutomirski <luto-AT-mit.edu>, Will Drewry <wad-AT-chromium.org>, linux-kernel-AT-vger.kernel.org, keescook-AT-chromium.org, john.johansen-AT-canonical.com, serge.hallyn-AT-canonical.com, coreyb-AT-linux.vnet.ibm.com, pmoore-AT-redhat.com, eparis-AT-redhat.com, djm-AT-mindrot.org, segoon-AT-openwall.com, rostedt-AT-goodmis.org, jmorris-AT-namei.org, scarybeasts-AT-gmail.com, avi-AT-redhat.com, penberg-AT-cs.helsinki.fi, viro-AT-zeniv.linux.org.uk, mingo-AT-elte.hu, akpm-AT-linux-foundation.org, khilman-AT-ti.com, borislav.petkov-AT-amd.com, amwang-AT-redhat.com, oleg-AT-redhat.com, ak-AT-linux.intel.com, eric.dumazet-AT-gmail.com, gregkh-AT-suse.de, dhowells-AT-redhat.com, daniel.lezcano-AT-free.fr, linux-fsdevel-AT-vger.kernel.org, linux-security-module-AT-vger.kernel.org, olofj-AT-chromium.org, mhalcrow-AT-google.com, dlaor-AT-redhat.com, corbet-AT-lwn.net, alan-AT-lxorguk.ukuu.org.uk|
On Sat, Jan 14, 2012 at 5:30 AM, Jamie Lokier <email@example.com> wrote: > > Anyway the principle is there - CAP_NET_BIND doesn't necessarily mean > the daemon code is trusted. I really think all these arguments are *COMPLETELY* missing the point. You don't have to use the new flag if you don't want to. Just let it go. The point of the flag is to not allow security changes. It's that easy. If you want something else, don't use it. Because even "dropping capabilities" is quite often the wrong thing to do. To one person it's "dropping capabilities", to another it is "no longer running with the capabilities I need". We've had security bugs that were *due* to dropped capabilities - people dropped one capability but not another, and fooled code into doing things they weren't expecting it to do. So quite frankly, I believe that from a security standpoint it's a hell of a lot safer to just keep the rules really simple. Think of the "restrict" bit as "my universe will now run with this *known* set of permissions". And if you don't like it, don't use it. It really is that simple. But don't make the model more complicated. Don't confuse it with "but but capabilites" crap. The point of the patch is that it makes all of that go away. There are no capabilities. There only is what you can do. And yes, I really seriously do believe that is both safer and simpler than some model that says "you can drop stuff", and then you have to start making up rules for what "dropping" means. Does "dropping" mean allowing setuid(geteuid()) for example? That *is* dropping the uid in a _POSIX_SAVED_IDS environment. And I'm saying that no, we should not even allow that. It's simply all too "subtle". (I don't think Andrew's patch actually touched any of those paths, but I didn't check) Linus -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to firstname.lastname@example.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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