Commit 64db4c7f authored May 02, 2017 by Kirill Tkhai Committed by Eric W. Biederman Jul 20, 2017

security: Use user_namespace::level to avoid redundant iterations in cap_capable()



When ns->level is not larger then cred->user_ns->level,
then ns can't be cred->user_ns's descendant, and
there is no a sense to search in parents.

So, break the cycle earlier and skip needless iterations.

v2: Change comment on suggested by Andy Lutomirski.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

parent a2b42626

security/commoncap.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -82,8 +82,11 @@ int cap_capable(const struct cred cred, struct user_namespace targ_ns,
		if (ns == cred->user_ns)
		return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;

		/* Have we tried all of the parent namespaces? */
		if (ns == &init_user_ns)
		/*
		* If we're already at a lower level than we're looking for,
		* we're done searching.
		*/
		if (ns->level <= cred->user_ns->level)
		return -EPERM;

		/*