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>
diff --git a/security/commoncap.c b/security/commoncap.c
index 7abebd7..d593202 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -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;
/*