From patchwork Fri Jul 23 22:50:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 485133 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 A0791C4320A for ; Fri, 23 Jul 2021 22:50:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82D3A60F36 for ; Fri, 23 Jul 2021 22:50:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232909AbhGWWJj (ORCPT ); Fri, 23 Jul 2021 18:09:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:49198 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231954AbhGWWJj (ORCPT ); Fri, 23 Jul 2021 18:09:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7F39560EB5; Fri, 23 Jul 2021 22:50:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1627080611; bh=xpuL7eQJ7xIPE/XkgeA272A2+E7I7sd5biWYgp+buAw=; h=Date:From:To:Subject:In-Reply-To:From; b=AJJZqaI5Bfft/bWGO1YiP4dhQEbOZH/9BzClDlW/vYxzKmHONpSrgTH1RW/yMlufC n2GokPJWggESxvNkdmzeZbDYIFtocQoVYAY/DIOGnnFD7Hym4FK3D+ELushuwhNVUT yV3tq/6jrs9iYnCigvx0cGo/uJ20vsQ0VuleLJ24= Date: Fri, 23 Jul 2021 15:50:11 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dvyukov@google.com, elver@google.com, glider@google.com, gregkh@linuxfoundation.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 04/15] kfence: move the size check to the beginning of __kfence_alloc() Message-ID: <20210723225011.pURAgvl2s%akpm@linux-foundation.org> In-Reply-To: <20210723154926.c6cda0f262b1990b950a5886@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Alexander Potapenko Subject: kfence: move the size check to the beginning of __kfence_alloc() Check the allocation size before toggling kfence_allocation_gate. This way allocations that can't be served by KFENCE will not result in waiting for another CONFIG_KFENCE_SAMPLE_INTERVAL without allocating anything. Link: https://lkml.kernel.org/r/20210714092222.1890268-1-glider@google.com Signed-off-by: Alexander Potapenko Suggested-by: Marco Elver Reviewed-by: Marco Elver Cc: Dmitry Vyukov Cc: Marco Elver Cc: Greg Kroah-Hartman Cc: [5.12+] Signed-off-by: Andrew Morton --- mm/kfence/core.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/mm/kfence/core.c~kfence-move-the-size-check-to-the-beginning-of-__kfence_alloc +++ a/mm/kfence/core.c @@ -734,6 +734,13 @@ void kfence_shutdown_cache(struct kmem_c void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) { /* + * Perform size check before switching kfence_allocation_gate, so that + * we don't disable KFENCE without making an allocation. + */ + if (size > PAGE_SIZE) + return NULL; + + /* * allocation_gate only needs to become non-zero, so it doesn't make * sense to continue writing to it and pay the associated contention * cost, in case we have a large number of concurrent allocations. @@ -757,9 +764,6 @@ void *__kfence_alloc(struct kmem_cache * if (!READ_ONCE(kfence_enabled)) return NULL; - if (size > PAGE_SIZE) - return NULL; - return kfence_guarded_alloc(s, size, flags); }