Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull (again) user namespace infrastructure changes from Eric Biederman:
 "Those bugs, those darn embarrasing bugs just want don't want to get
  fixed.

  Linus I just updated my mirror of your kernel.org tree and it appears
  you successfully pulled everything except the last 4 commits that fix
  those embarrasing bugs.

  When you get a chance can you please repull my branch"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  userns: Fix typo in description of the limitation of userns_install
  userns: Add a more complete capability subset test to commit_creds
  userns: Require CAP_SYS_ADMIN for most uses of setns.
  Fix cap_capable to only allow owners in the parent user namespace to have caps.

1 files changed, 17 insertions, 8 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index 6dbae4650ab..7ee08c756d6 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -76,24 +76,33 @@ int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
 		int cap, int audit)
 {
-	for (;;) {
-		/* The owner of the user namespace has all caps. */
-		if (targ_ns != &init_user_ns && uid_eq(targ_ns->owner, cred->euid))
-			return 0;
+	struct user_namespace *ns = targ_ns;
 
+	/* See if cred has the capability in the target user namespace
+	 * by examining the target user namespace and all of the target
+	 * user namespace's parents.
+	 */
+	for (;;) {
 		/* Do we have the necessary capabilities? */
-		if (targ_ns == cred->user_ns)
+		if (ns == cred->user_ns)
 			return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
 
 		/* Have we tried all of the parent namespaces? */
-		if (targ_ns == &init_user_ns)
+		if (ns == &init_user_ns)
 			return -EPERM;
 
+		/* 
+		 * The owner of the user namespace in the parent of the
+		 * user namespace has all caps.
+		 */
+		if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
+			return 0;
+
 		/*
-		 *If you have a capability in a parent user ns, then you have
+		 * If you have a capability in a parent user ns, then you have
 		 * it over all children user namespaces as well.
 		 */
-		targ_ns = targ_ns->parent;
+		ns = ns->parent;
 	}
 
 	/* We never get here */