linux-kernel - [PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns

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Date:   Fri, 25 Mar 2022 12:21:27 +0100
From:   Petr Vorel <pvorel@...e.cz>
To:     linux-kernel@...r.kernel.org
Cc:     Petr Vorel <pvorel@...e.cz>,
        Christian Brauner <christian@...uner.io>,
        Alexey Gladkov <legion@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Vasily Averin <vvs@...tuozzo.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

Move MAX_PID_NS_LEVEL to ns_common.h and reuse it in check in
user_namespace.c.

Signed-off-by: Petr Vorel <pvorel@...e.cz>
---
Hi Christian, all,

I don't see putting MAX_PID_NS_LEVEL into ns_common.h as an elegant
solution but IMHO better than use a hardwired number or redefinition in
user_namespace.h.

Kind regards,
Petr

 include/linux/ns_common.h     | 3 +++
 include/linux/pid_namespace.h | 3 ---
 kernel/user_namespace.c       | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index 0f1d024bd958..173fab9dadf7 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h
@@ -4,6 +4,9 @@
 
 #include <linux/refcount.h>
 
+/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
+#define MAX_PID_NS_LEVEL 32
+
 struct proc_ns_operations;
 
 struct ns_common {
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 07481bb87d4e..f814068012d0 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -11,9 +11,6 @@
 #include <linux/ns_common.h>
 #include <linux/idr.h>
 
-/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
-#define MAX_PID_NS_LEVEL 32
-
 struct fs_pin;
 
 struct pid_namespace {
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 5481ba44a8d6..6ea6e263403d 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -87,7 +87,7 @@ int create_user_ns(struct cred *new)
 	int ret, i;
 
 	ret = -ENOSPC;
-	if (parent_ns->level > 32)
+	if (parent_ns->level > MAX_PID_NS_LEVEL)
 		goto fail;
 
 	ucounts = inc_user_namespaces(parent_ns, owner);
-- 
2.35.1