linux-kernel - [PATCH 4.4 040/103] pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns

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Message-Id: <20170523200900.480278614@linuxfoundation.org>
Date:   Tue, 23 May 2017 22:09:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vovo Yang <vovoy@...gle.com>,
        Guenter Roeck <linux@...ck-us.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 4.4 040/103] pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric W. Biederman <ebiederm@...ssion.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@...gle.com>
Reported-by: Guenter Roeck <linux@...ck-us.net>
Tested-by: Guenter Roeck <linux@...ck-us.net>
Fixes: 6347e9009104 ("pidns: guarantee that the pidns init will be the last pidns process reaped")
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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();