Cache user_ns in struct cred
If !CONFIG_USERNS, have current_user_ns() defined to (&init_user_ns).
Get rid of _current_user_ns. This requires nsown_capable() to be
defined in capability.c rather than as static inline in capability.h,
so do that.
Request_key needs init_user_ns defined at current_user_ns if
!CONFIG_USERNS, so forward-declare that in cred.h if !CONFIG_USERNS
at current_user_ns() define.
Compile-tested with and without CONFIG_USERNS.
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
[ This makes a huge performance difference for acl_permission_check(),
up to 30%. And that is one of the hottest kernel functions for loads
that are pathname-lookup heavy. ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cred.c b/kernel/cred.c
index 5557b55..8093c16 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -54,6 +54,7 @@
.cap_effective = CAP_INIT_EFF_SET,
.cap_bset = CAP_INIT_BSET,
.user = INIT_USER,
+ .user_ns = &init_user_ns,
.group_info = &init_groups,
#ifdef CONFIG_KEYS
.tgcred = &init_tgcred,
@@ -410,6 +411,11 @@
goto error_put;
}
+ /* cache user_ns in cred. Doesn't need a refcount because it will
+ * stay pinned by cred->user
+ */
+ new->user_ns = new->user->user_ns;
+
#ifdef CONFIG_KEYS
/* new threads get their own thread keyrings if their parent already
* had one */
@@ -741,12 +747,6 @@
}
EXPORT_SYMBOL(set_create_files_as);
-struct user_namespace *current_user_ns(void)
-{
- return _current_user_ns();
-}
-EXPORT_SYMBOL(current_user_ns);
-
#ifdef CONFIG_DEBUG_CREDENTIALS
bool creds_are_invalid(const struct cred *cred)