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time/namespace: Add max_time_namespaces ucount

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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: 769071ac9f ("ns: Introduce Time Namespace")
Reported-by: Michael Kerrisk (man-pages) <mtk.manpages@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andrei Vagin <avagin@gmail.com>
Acked-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: stable@kernel.org
Link: https://lkml.kernel.org/r/20200406171342.128733-1-dima@arista.com
This commit is contained in:
Dmitry Safonov 2020-04-06 18:13:42 +01:00 committed by Thomas Gleixner
parent b801f1e22c
commit eeec26d5da
2 changed files with 7 additions and 0 deletions
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6
Documentation/admin-guide/sysctl/user.rst
View File

@ -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
===================

1
kernel/ucount.c
View File

@ -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"),