HID: fix HIDIOCGRDESC memory access in hidraw

Fix bogus copying of data into userspace when HIDIOCGRDESC is issued.
HID-transport layer makes sure that dev->hid->rdesc is not larger than
HID_MAX_DESCRIPTOR_SIZE.

Noticed-by: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index 8503197a8131..a702e2f6da7d 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -229,9 +229,15 @@ static int hidraw_ioctl(struct inode *inode, struct file *file, unsigned int cmd
 
                                 if (get_user(len, (int __user *)arg))
                                         return -EFAULT;
-                                if (copy_to_user(*((__u8 **)(user_arg +
-                                                        sizeof(__u32))),
-                                                        dev->hid->rdesc, len))
+
+                                if (len > HID_MAX_DESCRIPTOR_SIZE - 1)
+                                        return -EINVAL;
+
+                                if (copy_to_user(user_arg + offsetof(
+                                                                struct hidraw_report_descriptor,
+                                                                value[0]),
+                                                        dev->hid->rdesc,
+                                                        min(dev->hid->rsize, len)))
                                                 return -EFAULT;
                                 return 0;
                         }