staging: lustre: validate size in ll_setxattr()

If size is smaller than the lov_user_md struct then we are reading
beyond the end of the buffer.  I guess this is an information leak or it
could cause an Oops if the memory is not mapped.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/xattr.c

@@ -234,6 +234,9 @@ int ll_setxattr(struct dentry *dentry, const char *name,
 		struct lov_user_md *lump = (struct lov_user_md *)value;
 		int rc = 0;
 
+		if (size != 0 && size < sizeof(struct lov_user_md))
+			return -EINVAL;
+
 		/* Attributes that are saved via getxattr will always have
 		 * the stripe_offset as 0.  Instead, the MDS should be
 		 * allowed to pick the starting OST index.   b=17846 */