On Tue, May 2, 2017 at 5:40 AM, Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote: > 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; This is a nice improvement, but the comment could be better. How about "If we're already at a lower level than we're looking for, we're done searching." --Andy
