linux-kernel - [32/49] HID: hidraw: fix window in hidraw

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Message-Id: <20110105230326.680530408@clark.site>
Date:	Wed, 05 Jan 2011 15:00:50 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Jiri Slaby <jslaby@...e.cz>, Jiri Kosina <jkosina@...e.cz>,
	Antonio Ospite <ospite@...denti.unina.it>
Subject: [32/49] HID: hidraw: fix window in hidraw_release

2.6.32-longterm review patch.  If anyone has any objections, please let us know.

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

From: Jiri Slaby <jslaby@...e.cz>

commit cb174681a9ececa6702f114b85bdf82144b6a5af upstream.

[ Backport to .32.y by Antonio Ospite <ospite@...denti.unina.it> ]

There is a window between hidraw_table check and its dereference.
In that window, the device may be unplugged and removed form the
system and we will then dereference NULL.

Lock that place properly so that either we get NULL and jump out or we
can work with real pointer.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Antonio Ospite <ospite@...denti.unina.it>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/hid/hidraw.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -211,11 +211,14 @@ static int hidraw_release(struct inode *
 	unsigned int minor = iminor(inode);
 	struct hidraw *dev;
 	struct hidraw_list *list = file->private_data;
+	int ret;
 
+	mutex_lock(&minors_lock);
 	if (!hidraw_table[minor]) {
 		printk(KERN_EMERG "hidraw device with minor %d doesn't exist\n",
 				minor);
-		return -ENODEV;
+		ret = -ENODEV;
+		goto unlock;
 	}
 
 	list_del(&list->node);
@@ -229,10 +232,12 @@ static int hidraw_release(struct inode *
 			kfree(list->hidraw);
 		}
 	}
-
 	kfree(list);
+	ret = 0;
+unlock:
+	mutex_unlock(&minors_lock);
 
-	return 0;
+	return ret;
 }
 
 static long hidraw_ioctl(struct file *file, unsigned int cmd,


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