From patchwork Mon Oct 19 19:19:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 287108 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 16186C433E7 for ; Mon, 19 Oct 2020 19:19:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B30EE22365 for ; Mon, 19 Oct 2020 19:19:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731189AbgJSTTh (ORCPT ); Mon, 19 Oct 2020 15:19:37 -0400 Received: from smtp.infotech.no ([82.134.31.41]:56029 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731050AbgJSTTf (ORCPT ); Mon, 19 Oct 2020 15:19:35 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id D147120424C; Mon, 19 Oct 2020 21:19:33 +0200 (CEST) X-Virus-Scanned: by amavisd-new-2.6.6 (20110518) (Debian) at infotech.no Received: from smtp.infotech.no ([127.0.0.1]) by localhost (smtp.infotech.no [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id fvOafr9rN6Kg; Mon, 19 Oct 2020 21:19:33 +0200 (CEST) Received: from xtwo70.bingwo.ca (vpn.infotech.no [82.134.31.155]) by smtp.infotech.no (Postfix) with ESMTPA id 845D520414F; Mon, 19 Oct 2020 21:19:32 +0200 (CEST) From: Douglas Gilbert To: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: martin.petersen@oracle.com, axboe@kernel.dk, bvanassche@acm.org, bostroesser@gmail.com Subject: [PATCH v3 1/4] sgl_alloc_order: remove 4 GiB limit, sgl_free() warning Date: Mon, 19 Oct 2020 15:19:25 -0400 Message-Id: <20201019191928.77845-2-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201019191928.77845-1-dgilbert@interlog.com> References: <20201019191928.77845-1-dgilbert@interlog.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org This patch removes a check done by sgl_alloc_order() before it starts any allocations. The comment before the removed code says: "Check for integer overflow" arguably gives a false sense of security. The right hand side of the expression in the condition is resolved as u32 so cannot exceed UINT32_MAX (4 GiB) which means 'length' cannot exceed that amount. If that was the intention then the comment above it could be dropped and the condition rewritten more clearly as: if (length > UINT32_MAX) <>; The author's intention is to use sgl_alloc_order() to replace vmalloc(unsigned long) for a large allocation (debug ramdisk). vmalloc has no limit at 4 GiB so its seems unreasonable that: sgl_alloc_order(unsigned long long length, ....) does. sgl_s made with sgl_alloc_order(chainable=false) have equally sized segments placed in a scatter gather array. That allows O(1) navigation around a big sgl using some simple integer maths. Having previously sent a patch to fix a memory leak in sg_alloc_order() take the opportunity to put a one line comment above sgl_free()'s declaration that it is not suitable when order > 0 . The mis-use of sgl_free() when order > 0 was the reason for the memory leak. The other users of sgl_alloc_order() in the kernel where checked and found to handle free-ing properly. Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 1 + lib/scatterlist.c | 3 --- 2 files changed, 1 insertion(+), 3 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 45cf7b69d852..80178afc2a4a 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -302,6 +302,7 @@ struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, unsigned int *nent_p); void sgl_free_n_order(struct scatterlist *sgl, int nents, int order); void sgl_free_order(struct scatterlist *sgl, int order); +/* Only use sgl_free() when order is 0 */ void sgl_free(struct scatterlist *sgl); #endif /* CONFIG_SGL_ALLOC */ diff --git a/lib/scatterlist.c b/lib/scatterlist.c index c448642e0f78..d5770e7f1030 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -493,9 +493,6 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, u32 elem_len; nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); - /* Check for integer overflow */ - if (length > (nent << (PAGE_SHIFT + order))) - return NULL; nalloc = nent; if (chainable) { /* Check for integer overflow */