user namespaces: require cap_set{ug}id for CLONE_NEWUSER

thoughts? (patch is on top of
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6.git#next)

thanks,
-serge

Subject: [PATCH] user namespaces: require cap_set{ug}id for CLONE_NEWUSER

While ideally CLONE_NEWUSER will eventually require no privilege, the required permission checks are currently not there. As a result, CLONE_NEWUSER has the same effect as a setuid(0)+setgroups(1,"0"). While we already require CAP_SYS_ADMIN, requiring CAP_SETUID and CAP_SETGID seems appropriate.

---

 kernel/fork.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

32c36be0621dba3bf05af3d2df843ce803d25831

index 1dd8945..e3a85b3 100644
@@ -1344,7 +1344,8 @@ long do_fork(unsigned long clone_flags,
 		/* hopefully this check will go away when userns support is
 		 * complete
 		 */
-		if (!capable(CAP_SYS_ADMIN))
+		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
+				!capable(CAP_SETGID))
 			return -EPERM;
 	}
 

1.1.6