linux-kernel - [PATCH] messages: i2o: fix deadlock in compat

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Date:	Sat,  1 Feb 2014 02:29:48 +0400
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: [PATCH] messages: i2o: fix deadlock in compat_ioctl(I2OGETIOPS)

i2o_cfg_compat_ioctl(I2OGETIOPS) locks i2o_cfg_mutex and then calls
i2o_cfg_ioctl(I2OGETIOPS) that locks i2o_cfg_mutex as well.
A deadlock is guaranteed.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
---
 drivers/message/i2o/i2o_config.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/message/i2o/i2o_config.c b/drivers/message/i2o/i2o_config.c
index a60c188c2bd9..04bd3b6de401 100644
--- a/drivers/message/i2o/i2o_config.c
+++ b/drivers/message/i2o/i2o_config.c
@@ -754,19 +754,19 @@ static long i2o_cfg_compat_ioctl(struct file *file, unsigned cmd,
 				 unsigned long arg)
 {
 	int ret;
-	mutex_lock(&i2o_cfg_mutex);
 	switch (cmd) {
 	case I2OGETIOPS:
 		ret = i2o_cfg_ioctl(file, cmd, arg);
 		break;
 	case I2OPASSTHRU32:
+		mutex_lock(&i2o_cfg_mutex);
 		ret = i2o_cfg_passthru32(file, cmd, arg);
+		mutex_unlock(&i2o_cfg_mutex);
 		break;
 	default:
 		ret = -ENOIOCTLCMD;
 		break;
 	}
-	mutex_unlock(&i2o_cfg_mutex);
 	return ret;
 }
 
-- 
1.8.3.2

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