From mboxrd@z Thu Jan 1 00:00:00 1970 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=ham 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 4C3E5C4320A for ; Fri, 20 Aug 2021 02:04:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 343F1610FE for ; Fri, 20 Aug 2021 02:04:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236943AbhHTCFJ (ORCPT ); Thu, 19 Aug 2021 22:05:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:56796 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234428AbhHTCFH (ORCPT ); Thu, 19 Aug 2021 22:05:07 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 840B461056; Fri, 20 Aug 2021 02:04:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1629425070; bh=FAbgX98AcgWnC66yUp/bgSzwqTVgDkEDzHuEwn3Fbw0=; h=Date:From:To:Subject:In-Reply-To:From; b=a7Ir5CfHyUv4BhHr9giy0OFZ2b/aQdUfMhbhDc4MJSFAkzsDPXN9LGd+SkZibvEIi mKnH0VmwQ3f24y+BYCeKfHvnGaTGTVQ8QDJ2hn8FmHFO2iXNHhI6ImWUO61PmM00iE LAqw24/UsYPSY3tVB4HYkfVRc57ZYs3ONtCxx3kU= Date: Thu, 19 Aug 2021 19:04:30 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dvyukov@google.com, elver@google.com, glider@google.com, Kuan-Ying.Lee@mediatek.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 09/10] kfence: fix is_kfence_address() for addresses below KFENCE_POOL_SIZE Message-ID: <20210820020430.mQDxQa8Jr%akpm@linux-foundation.org> In-Reply-To: <20210819190327.14fc4e97102e1af7929e30af@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Marco Elver Subject: kfence: fix is_kfence_address() for addresses below KFENCE_POOL_SIZE Originally the addr != NULL check was meant to take care of the case where __kfence_pool == NULL (KFENCE is disabled). However, this does not work for addresses where addr > 0 && addr < KFENCE_POOL_SIZE. This can be the case on NULL-deref where addr > 0 && addr < PAGE_SIZE or any other faulting access with addr < KFENCE_POOL_SIZE. While the kernel would likely crash, the stack traces and report might be confusing due to double faults upon KFENCE's attempt to unprotect such an address. Fix it by just checking that __kfence_pool != NULL instead. Link: https://lkml.kernel.org/r/20210818130300.2482437-1-elver@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Marco Elver Reported-by: Kuan-Ying Lee Acked-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: [5.12+] Signed-off-by: Andrew Morton --- include/linux/kfence.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/include/linux/kfence.h~kfence-fix-is_kfence_address-for-addresses-below-kfence_pool_size +++ a/include/linux/kfence.h @@ -51,10 +51,11 @@ extern atomic_t kfence_allocation_gate; static __always_inline bool is_kfence_address(const void *addr) { /* - * The non-NULL check is required in case the __kfence_pool pointer was - * never initialized; keep it in the slow-path after the range-check. + * The __kfence_pool != NULL check is required to deal with the case + * where __kfence_pool == NULL && addr < KFENCE_POOL_SIZE. Keep it in + * the slow-path after the range-check! */ - return unlikely((unsigned long)((char *)addr - __kfence_pool) < KFENCE_POOL_SIZE && addr); + return unlikely((unsigned long)((char *)addr - __kfence_pool) < KFENCE_POOL_SIZE && __kfence_pool); } /** _