Commit 64db4c7f authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Eric W. Biederman

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: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent a2b42626
......@@ -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;
/*
......
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