Patch "pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pid_ns-sleep-in-task_interruptible-in-zap_pid_ns_processes.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From b9a985db98961ae1ba0be169f19df1c567e4ffe0 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Thu, 11 May 2017 18:21:01 -0500
Subject: pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

From: Eric W. Biederman <ebiederm@xmission.com>

commit b9a985db98961ae1ba0be169f19df1c567e4ffe0 upstream.

The code can potentially sleep for an indefinite amount of time in
zap_pid_ns_processes triggering the hung task timeout, and increasing
the system average.  This is undesirable.  Sleep with a task state of
TASK_INTERRUPTIBLE instead of TASK_UNINTERRUPTIBLE to remove these
undesirable side effects.

Apparently under heavy load this has been allowing Chrome to trigger
the hung time task timeout error and cause ChromeOS to reboot.

Reported-by: Vovo Yang <vovoy@google.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 6347e9009104 ("pidns: guarantee that the pidns init will be the last pidns process reaped")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/pid_namespace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -255,7 +255,7 @@ void zap_pid_ns_processes(struct pid_nam
 	 * if reparented.
 	 */
 	for (;;) {
-		set_current_state(TASK_UNINTERRUPTIBLE);
+		set_current_state(TASK_INTERRUPTIBLE);
 		if (pid_ns->nr_hashed == init_pids)
 			break;
 		schedule();


Patches currently in stable-queue which might be from ebiederm@xmission.com are

queue-4.4/proc-fix-unbalanced-hard-link-numbers.patch
queue-4.4/pid_ns-sleep-in-task_interruptible-in-zap_pid_ns_processes.patch
queue-4.4/pid_ns-fix-race-between-setns-ed-fork-and-zap_pid_ns_processes.patch