On Thu, Mar 14, 2013 at 1:29 PM, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes: > >> On 03/13/2013 11:35 AM, Eric W. Biederman wrote: >>> Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@xxxxxxxxxxxxxxxx> writes: >>> >>>> Hi, >>>> >>>> It seem like we should block (at least) this combination. On 3.9, this >>>> exploit works once uidmapping is added. >>>> >>>> http://www.openwall.com/lists/oss-security/2013/03/13/10 >>> >>> Yes. That is a bad combination. It let's chroot confuse privileged >>> processes. >>> >>> Now to figure out if this is easier to squash by adding a user_namespace >>> to fs_struct or by just forbidding this combination. >> >> It's worth making sure that setns(2) doesn't have similar issues. > > setns(2) and unshare(2) are done and merged. See commit. > > commit e66eded8309ebf679d3d3c1f5820d1f2ca332c71 > Author: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> > Date: Wed Mar 13 11:51:49 2013 -0700 > > userns: Don't allow CLONE_NEWUSER | CLONE_FS > > >> Looking through other shared-but-not-a-namespace things, there are: >> >> fs_struct: Buggy as noted. >> >> files_struct: Probably harmless -- SCM_RIGHTS can emulate it >> >> signal_struct: This interacts with the tty code. Is it okay? > > It should be. The tty code is heavily pid based, and CLONE_NEWPID > requires !CLONE_VM (which implies !CLONE_SIGHAND and !CLONE_VM). > >> sighand_struct: Looks safe. Famous last words. >> >> FWIW, I've been alarmed in the past that struct path (e.g. the root >> directory) implies an mnt_namespace (hidden in struct mount), and it's >> entirely possible for the root directory's mnt_namespace not to match >> nsproxy->mnt_namespace. I'm not sure what the implications are, but >> this doesn't seem healthy. > > The calls to check_mnt prevent abuse of the files found with fs_struct > not matching the current mount namespace. > > static inline int check_mnt(struct mount *mnt) > { > return mnt->mnt_ns == current->nsproxy->mnt_ns; > } > > Thanks for looking I know I did the same double take and wondered if I > had missed anything else by accident when this bug showed up. > > So far even just looking it all over again I can't see anything. But I > have clearly been blind before. This is way too fun. Got another one :/ I'll follow up in a sec off-list. --Andy _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
