linux-kernel - [PATCH v4 2/3] vt: fix locking around vt_bind/vt

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Message-Id: <1418681761-3709-2-git-send-email-imre.deak@intel.com>
Date:	Tue, 16 Dec 2014 00:16:00 +0200
From:	Imre Deak <imre.deak@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/3] vt: fix locking around vt_bind/vt_unbind

Currently vt_bind and vt_unbind access at least the con_driver object
and registered_con_driver array without holding the console lock. Fix
this by locking around the whole function in each case.

Signed-off-by: Imre Deak <imre.deak@...el.com>
Reviewed-by: Peter Hurley <peter@...leysoftware.com>
---
 drivers/tty/vt/vt.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 9c046fb..5d36c23 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3318,11 +3318,8 @@ static int vt_bind(struct con_driver *con)
 		if (first == 0 && last == MAX_NR_CONSOLES -1)
 			deflt = 1;
 
-		if (first != -1) {
-			console_lock();
+		if (first != -1)
 			do_bind_con_driver(csw, first, last, deflt);
-			console_unlock();
-		}
 
 		first = -1;
 		last = -1;
@@ -3362,9 +3359,7 @@ static int vt_unbind(struct con_driver *con)
 			deflt = 1;
 
 		if (first != -1) {
-			console_lock();
 			ret = do_unbind_con_driver(csw, first, last, deflt);
-			console_unlock();
 			if (ret != 0)
 				return ret;
 		}
@@ -3394,11 +3389,15 @@ static ssize_t store_bind(struct device *dev, struct device_attribute *attr,
 	struct con_driver *con = dev_get_drvdata(dev);
 	int bind = simple_strtoul(buf, NULL, 0);
 
+	console_lock();
+
 	if (bind)
 		vt_bind(con);
 	else
 		vt_unbind(con);
 
+	console_unlock();
+
 	return count;
 }
 
-- 
1.8.4

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