mei: validate request value in client notify request ioctl

This patch address a possible security issue:

The request field in client notify request ioctl comes from user space
as u32 and is downcasted to u8 with out validation.
Check request field to have approved values
MEI_HBM_NOTIFICATION_STAR/STOP

Cc: <stable@vger.kernel.org> #4.3+
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index 677d0362f334e842abb2c8c2439260978249b871..80f9afcb13823282a9859e08a96c36f55901efa6 100644 (file)
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -458,7 +458,11 @@ static int mei_ioctl_client_notify_request(struct file *file, u32 request)
 {
        struct mei_cl *cl = file->private_data;
 
-       return mei_cl_notify_request(cl, file, request);
+       if (request != MEI_HBM_NOTIFICATION_START &&
+           request != MEI_HBM_NOTIFICATION_STOP)
+               return -EINVAL;
+
+       return mei_cl_notify_request(cl, file, (u8)request);
 }
 
 /**