linux-kernel - [PATCH] ucount: Make sure ucounts in /proc/sys/user don't regress again

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Date:   Tue,  7 Apr 2020 17:46:43 +0200
From:   Jan Kara <jack@...e.cz>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrei Vagin <avagin@...il.com>, Jan Kara <jack@...e.cz>
Subject: [PATCH] ucount: Make sure ucounts in /proc/sys/user don't regress again

Commit 769071ac9f20 "ns: Introduce Time Namespace" broke reporting of
inotify ucounts (max_inotify_instances, max_inotify_watches) in
/proc/sys/user because it has added UCOUNT_TIME_NAMESPACES into enum
ucount_type but didn't properly update reporting in
kernel/ucount.c:setup_userns_sysctls(). This problem got fixed in commit
eeec26d5da82 "time/namespace: Add max_time_namespaces ucount". Add
BUILD_BUG_ON to catch a similar problem in the future.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 kernel/ucount.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/ucount.c b/kernel/ucount.c
index a53cc2b4179c..3da4d868e452 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -81,6 +81,8 @@ bool setup_userns_sysctls(struct user_namespace *ns)
 {
 #ifdef CONFIG_SYSCTL
 	struct ctl_table *tbl;
+
+	BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1);
 	setup_sysctl_set(&ns->set, &set_root, set_is_seen);
 	tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
 	if (tbl) {
-- 
2.16.4