From patchwork Tue Jun 1 18:22:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stephen Boyd X-Patchwork-Id: 12292063 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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 A11DBC47080 for ; Tue, 1 Jun 2021 18:22:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 55A3F613D1 for ; Tue, 1 Jun 2021 18:22:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 55A3F613D1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0294B6B0072; Tue, 1 Jun 2021 14:22:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 001356B0073; Tue, 1 Jun 2021 14:22:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D70326B0074; Tue, 1 Jun 2021 14:22:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0098.hostedemail.com [216.40.44.98]) by kanga.kvack.org (Postfix) with ESMTP id A5E1A6B0072 for ; Tue, 1 Jun 2021 14:22:11 -0400 (EDT) Received: from smtpin32.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 3DA97181AEF09 for ; Tue, 1 Jun 2021 18:22:11 +0000 (UTC) X-FDA: 78205974462.32.ED84462 Received: from mail-pf1-f175.google.com (mail-pf1-f175.google.com [209.85.210.175]) by imf23.hostedemail.com (Postfix) with ESMTP id 2754AA000262 for ; Tue, 1 Jun 2021 18:22:00 +0000 (UTC) Received: by mail-pf1-f175.google.com with SMTP id u18so130389pfk.11 for ; Tue, 01 Jun 2021 11:22:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=XPjY3p17RpdUxmvaUzvStFXowgAqs5bSM8U5J4753tM=; b=JdKbC5WayUy2DBLywV0jSbrlIjP/2nSMm9wzijAMUyrJfbt/taBTudIdXt9r2Q7J8+ LlAwIX8W7OjgLZCIgQ21bDoc7TAkhJOOynZgop0OLwTDkaFFdBIk//n7/kuf514UU4Vq RLKf6Fw9Ep1MDXX/3JOCXAt0xQL2GN94FRDk0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=XPjY3p17RpdUxmvaUzvStFXowgAqs5bSM8U5J4753tM=; b=cT+K9r/xIRzVaM2+tTm+rjb+S3iNDAL8SC7VRGafxiOfwpeXLziCHqWo/X4xciXAFf w1PZr0uBXL5kEA0QCDlyyM00R/BgvYQaUw02btrx6ddJtg15soPPMbxer1YI8XFRzg/H dFwzQK1A+3IuV+r2tgCDA2TlxqRk5G64g6mtE+QevLlV88ZamMGMywW1IENws946iLix JOF34AorCGz7vGuEHbbIPhMusn3E3XXPJcqC67kXkKntt8t3WZcgYKRpqy+YPZMfPr+R RAFrHwgJbcXIuNmzbJBvEWONDS1bHLGr1IXBH8tJ6CnPi7ixrmATl23iamo82k3wnMfA opUQ== X-Gm-Message-State: AOAM530lotHOeD9xRV5tuvVsBdNt10iwbKWiFPntvgMlu59UU7it9Lno 4rwS0ZeaK78Z6WACWUbJXpmw5w== X-Google-Smtp-Source: ABdhPJw35jzyT/JFV/F68qpD5e6asH7oVRjLNYleVcXFqZXGe2B72Cc7Y+nPOxbvoNAkIjfZYCR+ZQ== X-Received: by 2002:aa7:82c6:0:b029:2d8:9160:5942 with SMTP id f6-20020aa782c60000b02902d891605942mr22919323pfn.78.1622571730084; Tue, 01 Jun 2021 11:22:10 -0700 (PDT) Received: from smtp.gmail.com ([2620:15c:202:201:ee82:b2a7:c8bd:18e7]) by smtp.gmail.com with ESMTPSA id g29sm14510982pgm.11.2021.06.01.11.22.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Jun 2021 11:22:09 -0700 (PDT) From: Stephen Boyd To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org, Petr Mladek , Joe Perches Subject: [PATCH v3 4/4] slub: Force on no_hash_pointers when slub_debug is enabled Date: Tue, 1 Jun 2021 11:22:02 -0700 Message-Id: <20210601182202.3011020-5-swboyd@chromium.org> X-Mailer: git-send-email 2.32.0.rc0.204.g9fa02ecfa5-goog In-Reply-To: <20210601182202.3011020-1-swboyd@chromium.org> References: <20210601182202.3011020-1-swboyd@chromium.org> MIME-Version: 1.0 X-Rspamd-Queue-Id: 2754AA000262 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=JdKbC5Wa; spf=pass (imf23.hostedemail.com: domain of swboyd@chromium.org designates 209.85.210.175 as permitted sender) smtp.mailfrom=swboyd@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspamd-Server: rspam04 X-Stat-Signature: 86ho41mcebhkgo1m649gzh576eidtt8x X-HE-Tag: 1622571720-535438 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Obscuring the pointers that slub shows when debugging makes for some confusing slub debug messages: Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17 Those addresses are hashed for kernel security reasons. If we're trying to be secure with slub_debug on the commandline we have some big problems given that we dump whole chunks of kernel memory to the kernel logs. Let's force on the no_hash_pointers commandline flag when slub_debug is on the commandline. This makes slub debug messages more meaningful and if by chance a kernel address is in some slub debug object dump we will have a better chance of figuring out what went wrong. Note that we don't use %px in the slub code because we want to reduce the number of places that %px is used in the kernel. This also nicely prints a big fat warning at kernel boot if slub_debug is on the commandline so that we know that this kernel shouldn't be used on production systems. Signed-off-by: Stephen Boyd Reported-by: kernel test robot Acked-by: Vlastimil Babka Acked-by: Petr Mladek --- include/linux/kernel.h | 2 ++ lib/vsprintf.c | 2 +- mm/slub.c | 4 ++++ 3 files changed, 7 insertions(+), 1 deletion(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 15d8bad3d2f2..bf950621febf 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -357,6 +357,8 @@ int sscanf(const char *, const char *, ...); extern __scanf(2, 0) int vsscanf(const char *, const char *, va_list); +extern int no_hash_pointers_enable(char *str); + extern int get_option(char **str, int *pint); extern char *get_options(const char *str, int nints, int *ints); extern unsigned long long memparse(const char *ptr, char **retptr); diff --git a/lib/vsprintf.c b/lib/vsprintf.c index f0c35d9b65bf..cc281f5895f9 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2186,7 +2186,7 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode, bool no_hash_pointers __ro_after_init; EXPORT_SYMBOL_GPL(no_hash_pointers); -static int __init no_hash_pointers_enable(char *str) +int __init no_hash_pointers_enable(char *str) { if (no_hash_pointers) return 0; diff --git a/mm/slub.c b/mm/slub.c index bf4949115412..a722794f1dbd 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4460,6 +4460,10 @@ void __init kmem_cache_init(void) if (debug_guardpage_minorder()) slub_max_order = 0; + /* Print slub debugging pointers without hashing */ + if (static_branch_unlikely(&slub_debug_enabled)) + no_hash_pointers_enable(NULL); + kmem_cache_node = &boot_kmem_cache_node; kmem_cache = &boot_kmem_cache;