linux-kernel - [PATCH 2/8] sysrq: Properly check for kernel threads

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Date:	Tue, 7 Feb 2012 10:49:51 +0400
From:	Anton Vorontsov <anton.vorontsov@...aro.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Russell King <linux@....linux.org.uk>,
	Mike Frysinger <vapier@...too.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Richard Weinberger <richard@....at>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/8] sysrq: Properly check for kernel threads

There's a real possibility of killing kernel threads that might
have issued use_mm(), so kthread's mm might become non-NULL.

This patch fixes the issue by checking for PF_KTHREAD (just as
get_task_mm()).

Suggested-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
---
 drivers/tty/sysrq.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index a1bcad7..8db9125 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -324,9 +324,12 @@ static void send_sig_all(int sig)
 
 	read_lock(&tasklist_lock);
 	for_each_process(p) {
-		if (p->mm && !is_global_init(p))
-			/* Not swapper, init nor kernel thread */
-			force_sig(sig, p);
+		if (p->flags & PF_KTHREAD)
+			continue;
+		if (is_global_init(p))
+			continue;
+
+		force_sig(sig, p);
 	}
 	read_unlock(&tasklist_lock);
 }
-- 
1.7.7.6

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