linux-kernel - [PATCH] ucount: Fix wrong inotify ucounts in /proc/sys/user

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Date:   Tue,  7 Apr 2020 14:18:14 +0200
From:   Jan Kara <jack@...e.cz>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andrei Vagin <avagin@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
        stable@...r.kernel.org
Subject: [PATCH] ucount: Fix wrong inotify ucounts in /proc/sys/user

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(). Update the reporting to fix the
issue and also add BUILD_BUG_ON to catch a similar problem in the
future.

Fixes: 769071ac9f20 "ns: Introduce Time Namespace"
CC: stable@...r.kernel.org
Signed-off-by: Jan Kara <jack@...e.cz>
---
 kernel/ucount.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/ucount.c b/kernel/ucount.c
index a53cc2b4179c..11b1596e2542 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -69,6 +69,7 @@ static struct ctl_table user_table[] = {
 	UCOUNT_ENTRY("max_net_namespaces"),
 	UCOUNT_ENTRY("max_mnt_namespaces"),
 	UCOUNT_ENTRY("max_cgroup_namespaces"),
+	UCOUNT_ENTRY("max_time_namespaces"),
 #ifdef CONFIG_INOTIFY_USER
 	UCOUNT_ENTRY("max_inotify_instances"),
 	UCOUNT_ENTRY("max_inotify_watches"),
@@ -81,6 +82,8 @@ 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