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. 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..f6ef78208d2d 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 ns can't be a descendant of cred->user_ns, then it's + * needlessly to go up. + */ + if (ns->level <= cred->user_ns->level) return -EPERM; /*
