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 E651DC32771 for ; Mon, 26 Sep 2022 19:11:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 377C86B0083; Mon, 26 Sep 2022 15:11:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 328306B0085; Mon, 26 Sep 2022 15:11:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1C8818E0066; Mon, 26 Sep 2022 15:11:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 0E0BC6B0083 for ; Mon, 26 Sep 2022 15:11:37 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id C2A46A079E for ; Mon, 26 Sep 2022 19:11:36 +0000 (UTC) X-FDA: 79955180592.27.F8FC5B4 Received: from mail-qt1-f180.google.com (mail-qt1-f180.google.com [209.85.160.180]) by imf02.hostedemail.com (Postfix) with ESMTP id 5CC1680002 for ; Mon, 26 Sep 2022 19:11:36 +0000 (UTC) Received: by mail-qt1-f180.google.com with SMTP id b23so4704797qtr.13 for ; Mon, 26 Sep 2022 12:11:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=3CHGQtxrUEIPS7Vs0U1v3kZ+VKfNuIhTmwS0yCWeTpg=; b=lAXDle+Su5iIedDI7FHXawnjl90dFeb1jZZaEPLHvRqdvvLrpUFwWpTAVY25fmLQOo 4UqnDHubQ2DL2NHIOND/oVWuuaaSS+tciU+nOIxjS66briKaoAMQhA/JsKJviEKHvpxK VoPhicVo4xeTSbj2FA6e/hcVCo+SjHlYV/1P+UnTM8YYfh8ghN2IF6fIWx03f5a9TxRv 6rkfg0ti3tFPPZL6UaFZo/oabotXj2vQiVmGBuR5HR6780yknHkNlCMI5gIPm1D5uq0m +/1kW8l+XDPDs1nHJ3tGf4jjFOuSoexparptDEGwvXta01vU2fbTTkEJpO59bhDpHQ8t BxIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=3CHGQtxrUEIPS7Vs0U1v3kZ+VKfNuIhTmwS0yCWeTpg=; b=LS5oFvkiXQkdhabkLnjvovYrR21QpAVL23WIVNagP8YXfnVFq06qNsN4Gyhx5Py+W/ WgIJ+SepGosTo4+fAOYcoayd+nd/fUyrtcvnaLmGcUBvvJtaC7ESDcojBTralL0OtbzW 89I539zI8DL8n2hBYgCxXAWAP4KCF4qf8oObTO1Ehn2juN1R0uIbTHDEnjw6MtJwFsvX 3HnU+G9XAs1CEofsGiFLUBCdAdPlWaGU4LWflg7kZZYpzwSHXvj+LQElFgxlAdfxuoPb axmq2flihyMdezcdOwLur+BBHK7LU93SgG7QrE26eqWFu3iYBHqd+PW/oCLhMNC2g5/x CJbw== X-Gm-Message-State: ACrzQf0PeUR5FSoJ+EINPceH+HT6p+xx4mOF0noR8r79Fe2om4eOBzFC ++73S0e7+S7Qu0OucREaaRYth2AvgzxRdpaIqMQ= X-Google-Smtp-Source: AMsMyM4DxEiz89ji3Lc5oRG5694dzQn/VGO0wux19LGYCQ/Ji2nrHLaaP4YOTlHUNfaV/dsBpicKj5oVEOjyRVFPt+8= X-Received: by 2002:a05:622a:11cf:b0:35b:a369:cc3 with SMTP id n15-20020a05622a11cf00b0035ba3690cc3mr19317849qtk.11.1664219495572; Mon, 26 Sep 2022 12:11:35 -0700 (PDT) MIME-Version: 1.0 References: <20220913065423.520159-1-feng.tang@intel.com> <20220913065423.520159-3-feng.tang@intel.com> In-Reply-To: <20220913065423.520159-3-feng.tang@intel.com> From: Andrey Konovalov Date: Mon, 26 Sep 2022 21:11:24 +0200 Message-ID: Subject: Re: [PATCH v6 2/4] mm/slub: only zero the requested size of buffer for kzalloc To: Feng Tang Cc: Andrew Morton , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Dmitry Vyukov , Jonathan Corbet , Dave Hansen , Linux Memory Management List , LKML , kasan-dev , Kees Cook Content-Type: text/plain; charset="UTF-8" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664219496; 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=3CHGQtxrUEIPS7Vs0U1v3kZ+VKfNuIhTmwS0yCWeTpg=; b=ek4vNj1benVE3UuD/u3VcidlzzpWWH4SjzXRFQPp62Fqogai89SjeOpoqriCyIUvr38wx3 Ifh5RLuuJ+jFQGMC0zLAridN/9BwWQ3jwE7jrpaFKAeBXXNIAmeuP8d31wAiJr4vIeEA0M /fMFQ/GXF9QkG9JSYNlZk2Ad+Ys8BcQ= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=lAXDle+S; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf02.hostedemail.com: domain of andreyknvl@gmail.com designates 209.85.160.180 as permitted sender) smtp.mailfrom=andreyknvl@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664219496; a=rsa-sha256; cv=none; b=zNGgEQK/jJLG495iKTfG5Uq4x0wW4HSucVjY6LTIS515RM4EVBv6DdEMTLFIw4dNOntSUW Ia7JQX+B9l3L2wMINvYIDFrv4lTCeAfT8tVYWsMooEM7BRmwJP9yK/EzJzBHInXUkW5Hr9 XQYXSXy761JnxXUAVBv8xZTLnDylE8U= X-Rspam-User: Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=lAXDle+S; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf02.hostedemail.com: domain of andreyknvl@gmail.com designates 209.85.160.180 as permitted sender) smtp.mailfrom=andreyknvl@gmail.com X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5CC1680002 X-Stat-Signature: qwc4749ioffg9nrhudu6dt9ycgwnpkqs X-HE-Tag: 1664219496-400321 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 Tue, Sep 13, 2022 at 8:54 AM Feng Tang wrote: > Hi Feng, > 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 sanity check could be added to > the extra space later. I still don't like the idea of only zeroing the requested memory and not the whole object. Considering potential info-leak vulnerabilities. Can we only do this when SLAB_DEBUG is enabled? > Performance wise, smaller zeroing length also brings shorter > execution time, as shown from test data on various server/desktop > platforms. > > For kzalloc users who will call ksize() later and utilize this > extra space, please be aware that the space is not zeroed any > more. CC Kees > > Signed-off-by: Feng Tang > --- > mm/slab.c | 7 ++++--- > mm/slab.h | 5 +++-- > mm/slub.c | 10 +++++++--- > 3 files changed, 14 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 d0ef9dd44b71..3cf5adf63f48 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -730,7 +730,8 @@ 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) > { > size_t i; > > @@ -746,7 +747,7 @@ 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, orig_size); Note that when KASAN is enabled and has integrated init, it will initialize the whole object, which leads to an inconsistency with this change. > kmemleak_alloc_recursive(p[i], s->object_size, 1, > s->flags, flags); > } > diff --git a/mm/slub.c b/mm/slub.c > index c8ba16b3a4db..6f823e99d8b4 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3376,7 +3376,11 @@ 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; > } > @@ -3833,11 +3837,11 @@ 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 >