From: Dmitry Safonov dima@arista.com
commit eeec26d5da8248ea4e240b8795bb4364213d3247 upstream.
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") 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- Documentation/admin-guide/sysctl/user.rst | 6 ++++++ kernel/ucount.c | 1 + 2 files changed, 7 insertions(+)
--- 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 ===================
--- 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"),