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 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 33B87C11F64 for ; Tue, 29 Jun 2021 02:34:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 164BB61D03 for ; Tue, 29 Jun 2021 02:34:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231753AbhF2ChU (ORCPT ); Mon, 28 Jun 2021 22:37:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:58020 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231750AbhF2ChU (ORCPT ); Mon, 28 Jun 2021 22:37:20 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D09D261A2B; Tue, 29 Jun 2021 02:34:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1624934093; bh=VqQgY4n2gWm6hlmSggaX4/pFgWht4gF6KPNu9KOKny8=; h=Date:From:To:Subject:In-Reply-To:From; b=ggl0Qargyaw+2df9eQl0/Ow+NYEFfNKVAf2Uec1psUopuPz7qT3RTYrQ34mxm5VrA ACsoY04U00KakJwgDjyUyKJk/svnT5Di7nacKPQZotVQSj4lPq3uLKtELpJpWlej2J Y621dWgbN0dE1Xk2c8Pq4Tib3Ys6IbSpV+jN9OVY= Date: Mon, 28 Jun 2021 19:34:52 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cl@linux.com, iamjoonsoo.kim@lge.com, joe@perches.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, penberg@kernel.org, pmladek@suse.com, rientjes@google.com, songmuchun@bytedance.com, swboyd@chromium.org, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 030/192] slub: force on no_hash_pointers when slub_debug is enabled Message-ID: <20210629023452.xXbavb1ls%akpm@linux-foundation.org> In-Reply-To: <20210628193256.008961950a714730751c1423@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: Stephen Boyd Subject: slub: force on no_hash_pointers when slub_debug is enabled 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. [akpm@linux-foundation.org: fix build with CONFIG_SLUB_DEBUG=n] Link: https://lkml.kernel.org/r/20210601182202.3011020-5-swboyd@chromium.org Signed-off-by: Stephen Boyd Acked-by: Vlastimil Babka Acked-by: Petr Mladek Cc: Joe Perches Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Muchun Song Signed-off-by: Andrew Morton --- include/linux/kernel.h | 2 ++ lib/vsprintf.c | 2 +- mm/slub.c | 20 +++++++++++++++++++- 3 files changed, 22 insertions(+), 2 deletions(-) --- a/include/linux/kernel.h~slub-force-on-no_hash_pointers-when-slub_debug-is-enabled +++ a/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); --- a/lib/vsprintf.c~slub-force-on-no_hash_pointers-when-slub_debug-is-enabled +++ a/lib/vsprintf.c @@ -2186,7 +2186,7 @@ char *fwnode_string(char *buf, char *end 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; --- a/mm/slub.c~slub-force-on-no_hash_pointers-when-slub_debug-is-enabled +++ a/mm/slub.c @@ -118,12 +118,26 @@ */ #ifdef CONFIG_SLUB_DEBUG + #ifdef CONFIG_SLUB_DEBUG_ON DEFINE_STATIC_KEY_TRUE(slub_debug_enabled); #else DEFINE_STATIC_KEY_FALSE(slub_debug_enabled); #endif -#endif + +static inline bool __slub_debug_enabled(void) +{ + return static_branch_unlikely(&slub_debug_enabled); +} + +#else /* CONFIG_SLUB_DEBUG */ + +static inline bool __slub_debug_enabled(void) +{ + return false; +} + +#endif /* CONFIG_SLUB_DEBUG */ static inline bool kmem_cache_debug(struct kmem_cache *s) { @@ -4487,6 +4501,10 @@ void __init kmem_cache_init(void) if (debug_guardpage_minorder()) slub_max_order = 0; + /* Print slub debugging pointers without hashing */ + if (__slub_debug_enabled()) + no_hash_pointers_enable(NULL); + kmem_cache_node = &boot_kmem_cache_node; kmem_cache = &boot_kmem_cache; _