From patchwork Tue Feb 1 03:49:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 12731375 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 71686C433EF for ; Tue, 1 Feb 2022 03:49:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231984AbiBADtZ (ORCPT ); Mon, 31 Jan 2022 22:49:25 -0500 Received: from smtp.infotech.no ([82.134.31.41]:32817 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229518AbiBADtZ (ORCPT ); Mon, 31 Jan 2022 22:49:25 -0500 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id BAF4C2041BD; Tue, 1 Feb 2022 04:49:22 +0100 (CET) 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 ZC7obR1We4LR; Tue, 1 Feb 2022 04:49:19 +0100 (CET) Received: from xtwo70.bingwo.ca (host-45-78-195-155.dyn.295.ca [45.78.195.155]) by smtp.infotech.no (Postfix) with ESMTPA id 6A29D2041AC; Tue, 1 Feb 2022 04:49:18 +0100 (CET) From: Douglas Gilbert To: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com, hare@suse.de, bvanassche@acm.org, Jason Gunthorpe , Bodo Stroesser Subject: [PATCH v7 1/4] sgl_alloc_order: remove 4 GiB limit Date: Mon, 31 Jan 2022 22:49:12 -0500 Message-Id: <20220201034915.183117-2-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220201034915.183117-1-dgilbert@interlog.com> References: <20220201034915.183117-1-dgilbert@interlog.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org This patch fixes a check done by sgl_alloc_order() before it starts any allocations. The comment in the original said: "Check for integer overflow" but the right hand side of the expression in the condition is resolved as u32 so it can not exceed UINT32_MAX (4 GiB) which means 'length' can not exceed that value. This function may be used to replace vmalloc(unsigned long) for a large allocation (e.g. a ramdisk). vmalloc has no limit at 4 GiB so it seems unreasonable that sgl_alloc_order() whose length type is unsigned long long should be limited to 4 GB. In early 2021 there was discussion between Jason Gunthorpe and Bodo Stroesser about the way to check for overflow caused by order (an exponent) being too large. Take the solution proposed by Bodo in post dated 20210118 to the linux-scsi and linux-block lists. An earlier patch fixed a memory leak in sg_alloc_order() due to the misuse of sgl_free(). Take the opportunity to put a one line comment above sgl_free()'s declaration warning that it is not suitable when order > 0 . Cc: Jason Gunthorpe Reviewed-by: Bodo Stroesser Signed-off-by: Douglas Gilbert Reported-by: kernel test robot --- include/linux/scatterlist.h | 1 + lib/scatterlist.c | 24 +++++++++++++----------- 2 files changed, 14 insertions(+), 11 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 7ff9d6386c12..03130be581bb 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -357,6 +357,7 @@ 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 d5e82e4a57ad..ed6d0465c78e 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -585,13 +585,16 @@ EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); #ifdef CONFIG_SGL_ALLOC /** - * sgl_alloc_order - allocate a scatterlist and its pages + * sgl_alloc_order - allocate a scatterlist with equally sized elements each + * of which has 2^@order continuous pages * @length: Length in bytes of the scatterlist. Must be at least one - * @order: Second argument for alloc_pages() + * @order: Second argument for alloc_pages(). Each sgl element size will + * be (PAGE_SIZE*2^@order) bytes. @order must not exceed 16. * @chainable: Whether or not to allocate an extra element in the scatterlist - * for scatterlist chaining purposes + * for scatterlist chaining purposes * @gfp: Memory allocation flags - * @nent_p: [out] Number of entries in the scatterlist that have pages + * @nent_p: [out] Number of entries in the scatterlist that have pages. + * Ignored if @nent_p is NULL. * * Returns: A pointer to an initialized scatterlist or %NULL upon failure. */ @@ -604,16 +607,15 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, unsigned int nent, nalloc; u32 elem_len; - nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); - /* Check for integer overflow */ - if (length > (nent << (PAGE_SHIFT + order))) + if (length >> (PAGE_SHIFT + order) >= UINT_MAX) return NULL; - nalloc = nent; + nent = DIV_ROUND_UP(length, PAGE_SIZE << order); + if (chainable) { - /* Check for integer overflow */ - if (nalloc + 1 < nalloc) + if (check_add_overflow(nent, 1U, &nalloc)) return NULL; - nalloc++; + } else { + nalloc = nent; } sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), gfp & ~GFP_DMA);