linux-kernel - [095/127] HID: hidraw, fix a NULL pointer dereference in hidraw

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Date:	Tue, 07 Dec 2010 16:44:41 -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,
	Antonio Ospite <ospite@...denti.unina.it>,
	Jiri Kosina <jkosina@...e.cz>
Subject: [095/127] HID: hidraw, fix a NULL pointer dereference in hidraw_write

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

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

From: Antonio Ospite <ospite@...denti.unina.it>

commit e42dee9a99a3ecd32b5c027e8f7411fb5bc11eb6 upstream.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
IP: [<ffffffffa0f0a625>] hidraw_write+0x3b/0x116 [hid]
[...]

This is reproducible by disconnecting the device while userspace writes
to dev node in a loop and doesn't check return values in order to exit
the loop.

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

---
 drivers/hid/hidraw.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -105,11 +105,15 @@ out:
 static ssize_t hidraw_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
 {
 	unsigned int minor = iminor(file->f_path.dentry->d_inode);
-	/* FIXME: What stops hidraw_table going NULL */
-	struct hid_device *dev = hidraw_table[minor]->hid;
+	struct hid_device *dev;
 	__u8 *buf;
 	int ret = 0;
 
+	if (!hidraw_table[minor])
+		return -ENODEV;
+
+	dev = hidraw_table[minor]->hid;
+
 	if (!dev->hid_output_raw_report)
 		return -ENODEV;
 


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