linux-kernel - [PATCH 3.12 083/155] hung_task: check the value of "sysctl_hung_task_timeout

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Message-Id: <cd76af47a62031a1345945adaf14ba9ab70a6cd4.1428411004.git.jslaby@suse.cz>
Date:	Tue,  7 Apr 2015 14:50:52 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Liu Hua <sdu.liu@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 083/155] hung_task: check the value of "sysctl_hung_task_timeout_sec"

From: Liu Hua <sdu.liu@...wei.com>

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

===============

commit 80df28476505ed4e6701c3448c63c9229a50c655 upstream.

As sysctl_hung_task_timeout_sec is unsigned long, when this value is
larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
watchdog will return immediately without sleep and with print :

  schedule_timeout: wrong timeout value ffffffffffffff83

and then the funtion watchdog will call schedule_timeout_interruptible
again and again.  The screen will be filled with

	"schedule_timeout: wrong timeout value ffffffffffffff83"

This patch does some check and correction in sysctl, to let the function
schedule_timeout_interruptible allways get the valid parameter.

Signed-off-by: Liu Hua <sdu.liu@...wei.com>
Tested-by: Satoru Takeuchi <satoru.takeuchi@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 kernel/sysctl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 167741003616..6a9b0c42fb30 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -142,6 +142,11 @@ static int minolduid;
 static int ngroups_max = NGROUPS_MAX;
 static const int cap_last_cap = CAP_LAST_CAP;
 
+/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */
+#ifdef CONFIG_DETECT_HUNG_TASK
+static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
+#endif
+
 #ifdef CONFIG_INOTIFY_USER
 #include <linux/inotify.h>
 #endif
@@ -971,6 +976,7 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_dohung_task_timeout_secs,
+		.extra2		= &hung_task_timeout_max,
 	},
 	{
 		.procname	= "hung_task_warnings",
-- 
2.3.4

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