[PATCH 4.4 81/97] HID: hidraw: Fix crash on HIDIOCGFEATURE with a destroyed device

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Rodrigo Rivas Costa <rodrigorivascosta@xxxxxxxxx>

commit a955358d54695e4ad9f7d6489a7ac4d69a8fc711 upstream.

Doing `ioctl(HIDIOCGFEATURE)` in a tight loop on a hidraw device
and then disconnecting the device, or unloading the driver, can
cause a NULL pointer dereference.

When a hidraw device is destroyed it sets 0 to `dev->exist`.
Most functions check 'dev->exist' before doing its work, but
`hidraw_get_report()` was missing that check.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Rodrigo Rivas Costa <rodrigorivascosta@xxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/hid/hidraw.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -197,6 +197,11 @@ static ssize_t hidraw_get_report(struct
 	int ret = 0, len;
 	unsigned char report_number;
 
+	if (!hidraw_table[minor] || !hidraw_table[minor]->exist) {
+		ret = -ENODEV;
+		goto out;
+	}
+
 	dev = hidraw_table[minor]->hid;
 
 	if (!dev->ll_driver->raw_request) {