Date: Wed, 13 Mar 2013 18:33:00 -0700 From: Greg KH <gregkh@...uxfoundation.org> To: oss-security@...ts.openwall.com Subject: Re: CLONE_NEWUSER|CLONE_FS root exploit On Thu, Mar 14, 2013 at 09:03:20AM +0800, Eugene Teo wrote: > On 14 Mar, 2013, at 8:59 AM, Eugene Teo <eugeneteo@...nel.sg> wrote: > > > On 13 Mar, 2013, at 11:39 PM, Sebastian Krahmer <krahmer@...e.de> wrote: > > > >> Hi, > >> > >> Seems like CLONE_NEWUSER|CLONE_FS might be a forbidden > >> combination. > >> During evaluating the new user namespace thingie, it turned out > >> that its trivially exploitable to get a (real) uid 0, > >> as demonstrated here: > >> > >> http://stealth.openwall.net/xSports/clown-newuser.c > >> > >> The trick is to setup a chroot in your CLONE_NEWUSER, > >> but also affecting the parent, which is running > >> in the init_user_ns, but with the chroot shared. > >> Then its trivial to get a rootshell from that. > >> > >> Tested on a openSUSE12.1 with a custom build 3.8.2 (x86_64). > >> > >> I hope I didnt make anything wrong, mixing up the UIDs, > >> or disabled important checks during kernel build on my test > >> system. ;) > > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=aea8b5d1e5c5482e7cdda849dc16d728f7080289 > > I realised that the link is incorrect. Will post again when I see the patches. It is commit e66eded8309ebf679d3d3c1f5820d1f2ca332c71 in Linus's tree, so replace the sha in the above link with this one instead. Hope this helps, greg k-h
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