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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C98EC38A2D for ; Mon, 24 Oct 2022 14:01:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 109BF8E0002; Mon, 24 Oct 2022 10:01:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0B9B68E0001; Mon, 24 Oct 2022 10:01:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EC4888E0002; Mon, 24 Oct 2022 10:01:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id DAADD8E0001 for ; Mon, 24 Oct 2022 10:01:06 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 84F0E140DE1 for ; Mon, 24 Oct 2022 14:01:06 +0000 (UTC) X-FDA: 80056004532.13.4FC19C2 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) by imf15.hostedemail.com (Postfix) with ESMTP id D6025A0052 for ; Mon, 24 Oct 2022 14:01:03 +0000 (UTC) Received: by mail-pl1-f169.google.com with SMTP id n7so8538417plp.1 for ; Mon, 24 Oct 2022 07:01:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=54kX8KDXQhkF+Q470pyPNzIGi7dKEvffdL2ryBeituk=; b=P1UXV1aQ2xIn6+nfeoVYOCwP23g1rKm7rOqwVcSXyueYjNUUEjmr4djsO8Maj/xzlD ttEup0VfXhEmGqGMUpsC7DwrAbb7qwGHVJi3cdEWQGtKbUD2vpHTDXsjmSBytEfCMf9t MvMeXRyRdrDBAW0VXeXUEfydQTbrMKB3Y0Og5oHDWgVAw7eSwIUR43bOE3xgOvsjC/qx ObwEsZtmO0/C8uJSOv9M6XZ03SKmq/+Qrs+valNgrIEudc8d7reL/C2bqLnwJr+LGQ1y fJ+btOODQfPadp+0Slrk5WlePbWgVWUKb7YpkRPQj35M3lGc09ntgqWFY5cMMker4gHC YWKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=54kX8KDXQhkF+Q470pyPNzIGi7dKEvffdL2ryBeituk=; b=hRAypYNKSlc4D+qBP3cpDOx5OLHflHjTLeNKVJAhqWBPhgMtCHLA21tQorp8OXNkFq bNmoVqUUt1BdXG4vYfqKZF19GKWoQhtwjUqXXW//XBGKTM+qQ6xAYwO6u38z4apltIfU pM9n7iVa0Qhf71HjkcJktmjLYKbTLpWU6vKpmoWkwo8VUzi69A8eZe6caAJehJ+LvIg5 wKHXwgc0nkYSMyZnF9XkYtBCEaEoKB0WLo73awFJmKESYyH9f+VmSHIanZFY8vCCFLpT EPnwRH1axHAGNIZITcGBnekc0O9rGSB6tCEWXCRRP+9vGw5W+miEH0QFmGD/Piz1ZW6z P1rA== X-Gm-Message-State: ACrzQf33gqv6fQiRXNXyPvWqG0lHdDuK4/5dK7Nh7WN2DXFQX7UTqzXW yIBkvZJtnqB25BcALQGvmzc= X-Google-Smtp-Source: AMsMyM6qTovmErhU3eWJrcBLdokz9s5GdSBhO0/sG3Ym4jLAcqs32AzsS0NTOYpgLK7fBWs9iNsHtg== X-Received: by 2002:a17:903:18c:b0:186:994c:51b8 with SMTP id z12-20020a170903018c00b00186994c51b8mr9260281plg.44.1666620062372; Mon, 24 Oct 2022 07:01:02 -0700 (PDT) Received: from hyeyoo ([114.29.91.56]) by smtp.gmail.com with ESMTPSA id v7-20020a17090abb8700b001faf7a88138sm5712448pjr.42.2022.10.24.07.00.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Oct 2022 07:01:01 -0700 (PDT) Date: Mon, 24 Oct 2022 23:00:55 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Feng Tang Cc: Andrew Morton , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Dmitry Vyukov , Andrey Konovalov , Kees Cook , Dave Hansen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com Subject: Re: [PATCH v7 1/3] mm/slub: only zero requested size of buffer for kzalloc when debug enabled Message-ID: References: <20221021032405.1825078-1-feng.tang@intel.com> <20221021032405.1825078-2-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221021032405.1825078-2-feng.tang@intel.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666620063; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=54kX8KDXQhkF+Q470pyPNzIGi7dKEvffdL2ryBeituk=; b=tq3+5ZltOKglAn5+pSVFXiKSMDH9Xkt1CsQAqWvAm2JfKWqlVEDE2nQOjWVVQsc23wkCt5 GoJO9AmVo4NegV6LC9IKbqIZ90f0UTm4BWNyl6fx597GXvGAhfhZPmk+HXPw1CP+ZGZGL1 5XNl6KYiGuWHwnKpzLU11Pwd7ln+EaQ= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=P1UXV1aQ; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf15.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.214.169 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666620063; a=rsa-sha256; cv=none; b=PxMQL4XmizNh9H/8KfVpK+J7OYNfoOMu6k0GnVnESFZgVvSxDupOmNS22Koj6buaWdZAVG mSlYOU14EYl7Aqm3SvTjRww8dUAZIY/+gaPnGi+JhzZ/bLHYBDwdm1bgvNKHIWmIraYdoN vjvx4M1jhQvoTA2pbEZG/tbTElyaN0k= X-Rspam-User: Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=P1UXV1aQ; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf15.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.214.169 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com X-Rspamd-Server: rspam05 X-Stat-Signature: nddgwa4b7zt8kk7tzuje7p1bctfaka77 X-Rspamd-Queue-Id: D6025A0052 X-HE-Tag: 1666620063-521020 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: On Fri, Oct 21, 2022 at 11:24:03AM +0800, Feng Tang wrote: > kzalloc/kmalloc will round up the request size to a fixed size > (mostly power of 2), so the allocated memory could be more than > requested. Currently kzalloc family APIs will zero all the > allocated memory. > > To detect out-of-bound usage of the extra allocated memory, only > zero the requested part, so that redzone sanity check could be > added to the extra space later. > > For kzalloc users who will call ksize() later and utilize this > extra space, please be aware that the space is not zeroed any > more when debug is enabled. (Thanks to Kees Cook's effort to > sanitize all ksize() user cases [1], this won't be a big issue). > > [1]. https://lore.kernel.org/all/20220922031013.2150682-1-keescook@chromium.org/#r > Signed-off-by: Feng Tang > --- > mm/slab.c | 7 ++++--- > mm/slab.h | 18 ++++++++++++++++-- > mm/slub.c | 10 +++++++--- > 3 files changed, 27 insertions(+), 8 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index a5486ff8362a..4594de0e3d6b 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -3253,7 +3253,8 @@ slab_alloc_node(struct kmem_cache *cachep, struct list_lru *lru, gfp_t flags, > init = slab_want_init_on_alloc(flags, cachep); > > out: > - slab_post_alloc_hook(cachep, objcg, flags, 1, &objp, init); > + slab_post_alloc_hook(cachep, objcg, flags, 1, &objp, init, > + cachep->object_size); > return objp; > } > > @@ -3506,13 +3507,13 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, > * Done outside of the IRQ disabled section. > */ > slab_post_alloc_hook(s, objcg, flags, size, p, > - slab_want_init_on_alloc(flags, s)); > + slab_want_init_on_alloc(flags, s), s->object_size); > /* FIXME: Trace call missing. Christoph would like a bulk variant */ > return size; > error: > local_irq_enable(); > cache_alloc_debugcheck_after_bulk(s, flags, i, p, _RET_IP_); > - slab_post_alloc_hook(s, objcg, flags, i, p, false); > + slab_post_alloc_hook(s, objcg, flags, i, p, false, s->object_size); > kmem_cache_free_bulk(s, i, p); > return 0; > } > diff --git a/mm/slab.h b/mm/slab.h > index 0202a8c2f0d2..8b4ee02fc14a 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -720,12 +720,26 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, > > static inline void slab_post_alloc_hook(struct kmem_cache *s, > struct obj_cgroup *objcg, gfp_t flags, > - size_t size, void **p, bool init) > + size_t size, void **p, bool init, > + unsigned int orig_size) > { > + unsigned int zero_size = s->object_size; > size_t i; > > flags &= gfp_allowed_mask; > > + /* > + * For kmalloc object, the allocated memory size(object_size) is likely > + * larger than the requested size(orig_size). If redzone check is > + * enabled for the extra space, don't zero it, as it will be redzoned > + * soon. The redzone operation for this extra space could be seen as a > + * replacement of current poisoning under certain debug option, and > + * won't break other sanity checks. > + */ > + if (kmem_cache_debug_flags(s, SLAB_STORE_USER) && > + (s->flags & SLAB_KMALLOC)) > + zero_size = orig_size; > + > /* > * As memory initialization might be integrated into KASAN, > * kasan_slab_alloc and initialization memset must be > @@ -736,7 +750,7 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, > for (i = 0; i < size; i++) { > p[i] = kasan_slab_alloc(s, p[i], flags, init); > if (p[i] && init && !kasan_has_integrated_init()) > - memset(p[i], 0, s->object_size); > + memset(p[i], 0, zero_size); > kmemleak_alloc_recursive(p[i], s->object_size, 1, > s->flags, flags); > kmsan_slab_alloc(s, p[i], flags); > diff --git a/mm/slub.c b/mm/slub.c > index 12354fb8d6e4..17292c2d3eee 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3395,7 +3395,11 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, struct list_l > init = slab_want_init_on_alloc(gfpflags, s); > > out: > - slab_post_alloc_hook(s, objcg, gfpflags, 1, &object, init); > + /* > + * When init equals 'true', like for kzalloc() family, only > + * @orig_size bytes will be zeroed instead of s->object_size > + */ > + slab_post_alloc_hook(s, objcg, gfpflags, 1, &object, init, orig_size); > > return object; > } > @@ -3852,11 +3856,11 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, > * Done outside of the IRQ disabled fastpath loop. > */ > slab_post_alloc_hook(s, objcg, flags, size, p, > - slab_want_init_on_alloc(flags, s)); > + slab_want_init_on_alloc(flags, s), s->object_size); > return i; > error: > slub_put_cpu_ptr(s->cpu_slab); > - slab_post_alloc_hook(s, objcg, flags, i, p, false); > + slab_post_alloc_hook(s, objcg, flags, i, p, false, s->object_size); > kmem_cache_free_bulk(s, i, p); > return 0; > } > -- > 2.34.1 Looks good to me. Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> -- Thanks, Hyeonggon