From patchwork Sat Mar 26 14:50:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe JAILLET X-Patchwork-Id: 12792415 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70603C433F5 for ; Sat, 26 Mar 2022 14:50:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232291AbiCZOwb (ORCPT ); Sat, 26 Mar 2022 10:52:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44932 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232835AbiCZOw2 (ORCPT ); Sat, 26 Mar 2022 10:52:28 -0400 Received: from smtp.smtpout.orange.fr (smtp08.smtpout.orange.fr [80.12.242.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 336B32467F1 for ; Sat, 26 Mar 2022 07:50:51 -0700 (PDT) Received: from pop-os.home ([90.126.236.122]) by smtp.orange.fr with ESMTPA id Y7kdn2IzuxHdTY7kdnd4rD; Sat, 26 Mar 2022 15:50:49 +0100 X-ME-Helo: pop-os.home X-ME-Auth: YWZlNiIxYWMyZDliZWIzOTcwYTEyYzlhMmU3ZiQ1M2U2MzfzZDfyZTMxZTBkMTYyNDBjNDJlZmQ3ZQ== X-ME-Date: Sat, 26 Mar 2022 15:50:49 +0100 X-ME-IP: 90.126.236.122 From: Christophe JAILLET To: Jens Axboe , Hannes Reinecke , Jan Kara Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Christophe JAILLET , linux-block@vger.kernel.org Subject: [PATCH] block: Fix the maximum minor value is blk_alloc_ext_minor() Date: Sat, 26 Mar 2022 15:50:46 +0100 Message-Id: X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org ida_alloc_range(..., min, max, ...) returns values from min to max, inclusive. So, NR_EXT_DEVT is a valid idx returned by blk_alloc_ext_minor(). This is an issue because in device_add_disk(), this value is used in: ddev->devt = MKDEV(disk->major, disk->first_minor); and NR_EXT_DEVT is '(1 << MINORBITS)'. So, should 'disk->first_minor' be NR_EXT_DEVT, it would overflow. Fixes: 22ae8ce8b892 ("block: simplify bdev/disk lookup in blkdev_get") Signed-off-by: Christophe JAILLET Reviewed-by: Jan Kara --- #define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi)) This patch is completely speculative, but it seems that idr_alloc() and ida_alloc_range() don't have the same semantic regarding the upper bound. idr_alloc() looks exclusive, while ida_alloc_range() is inclusive. We changed from the first one to the other one in the commit in Fixes:. --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/genhd.c b/block/genhd.c index c9a4fc90d3e9..b8b6759d670f 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -335,7 +335,7 @@ int blk_alloc_ext_minor(void) { int idx; - idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT, GFP_KERNEL); + idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT - 1, GFP_KERNEL); if (idx == -ENOSPC) return -EBUSY; return idx;