[PATCH v2] security: Use user_namespace::level to avoid redundant iterations in cap_capable()
From: Kirill Tkhai
Date: Tue May 02 2017 - 13:12:11 EST
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 sence to search in parents.
So, breake the cycle earlier and skip needless iterations.
v2: Change comment on suggested by Andy Lutomirski.
Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
security/commoncap.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/security/commoncap.c b/security/commoncap.c
index 78b37838a2d3..a424aa0123af 100644
@@ -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)