Introduce missing time namespaces limit per-userns.
Michael noticed that userns limit for number of time namespaces is
missing.
Furthermore, time namespace introduced UCOUNT_TIME_NAMESPACES, but
didn't introduce an array member in user_table[]. It would make array's
initialisation OOB write, but by luck the user_table array has
an excessive empty member (all accesses to the array are limited with
UCOUNT_COUNTS - so it silently reuses the last free member.
Fixes user-visible regression: max_inotify_instances by reason of the
missing UCOUNT_ENTRY() has limited max number of namespaces instead of
the number of inotify instances.
Fixes: 769071ac9f20 ("ns: Introduce Time Namespace")
Cc: Adrian Reber <adrian@xxxxxxxx>
Cc: Andrey Vagin <avagin@xxxxxxxxxx>
Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Containers <containers@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Linux API <linux-api@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx # v5.6+
Reported-by: Michael Kerrisk (man-pages) <mtk.manpages@xxxxxxxxx>
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
---
Documentation/admin-guide/sysctl/user.rst | 6 ++++++
kernel/ucount.c | 1 +
2 files changed, 7 insertions(+)
diff --git a/Documentation/admin-guide/sysctl/user.rst b/Documentation/admin-guide/sysctl/user.rst
index 650eaa03f15e..c45824589339 100644
--- a/Documentation/admin-guide/sysctl/user.rst
+++ b/Documentation/admin-guide/sysctl/user.rst
@@ -65,6 +65,12 @@ max_pid_namespaces
The maximum number of pid namespaces that any user in the current
user namespace may create.
+max_time_namespaces
+===================
+
+ The maximum number of time namespaces that any user in the current
+ user namespace may create.
+
max_user_namespaces
===================
diff --git a/kernel/ucount.c b/kernel/ucount.c
index a53cc2b4179c..29c60eb4ec9b 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"),
--
2.26.0
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