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 0CED1C4345F for ; Thu, 25 Apr 2024 08:37:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 63F256B0083; Thu, 25 Apr 2024 04:37:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5EDFA6B0085; Thu, 25 Apr 2024 04:37:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4DCC86B0087; Thu, 25 Apr 2024 04:37:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 36A216B0083 for ; Thu, 25 Apr 2024 04:37:09 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id A426E1611F2 for ; Thu, 25 Apr 2024 08:37:08 +0000 (UTC) X-FDA: 82047399336.10.0E9D49B Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) by imf17.hostedemail.com (Postfix) with ESMTP id 2707A4000C for ; Thu, 25 Apr 2024 08:37:03 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=twvjcBTS; spf=pass (imf17.hostedemail.com: domain of chengming.zhou@linux.dev designates 95.215.58.187 as permitted sender) smtp.mailfrom=chengming.zhou@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1714034224; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=E8Dv8ja4cI4A7RuODPGz/1zq0mfPiA4Ztqb9IZnHmtE=; b=gLuOeUFgnEiAc7O7w1h7EEyIJx0pKvdW3L+fKrZ22rrWsY7eoee+sLumgCiv21l+0Ut0f2 z+R48MSBPp5rABSagLTMrIyvU7tF+XUlZNLMiqwcqaQR7J28zNy55yTOyRNe6Ve6+0fPtD 8uT4xcvg/E/iwBZBAnm70kf0Wk5J0gw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1714034224; a=rsa-sha256; cv=none; b=kFHhWUr5cBkf94Ntdwom99feCu0vao2lgIYF2Kv/JdzHhltMESzPgKOsItdtIwxoT/tdz6 DmPu/DxnltuU64wg/qceTTDC7IpGNEuFNssCAl2XdWFOX/efQmRxsmIyKhixG1ZDCioSwp 8YQrNE53cebx9WpnddVFg4WUHjm6BWc= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=twvjcBTS; spf=pass (imf17.hostedemail.com: domain of chengming.zhou@linux.dev designates 95.215.58.187 as permitted sender) smtp.mailfrom=chengming.zhou@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1714034221; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=E8Dv8ja4cI4A7RuODPGz/1zq0mfPiA4Ztqb9IZnHmtE=; b=twvjcBTST93NpvA3XgZgY6DoXLHBuOSyuy7O4G4p72MyO+AU4mK+Q4ipfbgJaTOxqwi+wB As0Sh3j+b8vDzwF2a3828/eq19a5mm3hIlNBT8qT1hI8c1kzyI5lZ/QPHD81rOQ6h1iowR DjdeZG/S09zYpPqYB6KVqVxu7dPBLjQ= Date: Thu, 25 Apr 2024 16:36:53 +0800 MIME-Version: 1.0 Subject: Re: [PATCH] slub: Fixes freepointer encoding for single free To: Nicolas Bouchinet , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com References: Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2707A4000C X-Stat-Signature: y1xoh5g3pq7npgoio53or63too9qyxf9 X-HE-Tag: 1714034223-565460 X-HE-Meta: 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 pVjs32s9 /cVFQ9xuGRugRJZTsbjpNRpXVWe/AllRk6G1GHIlfOYGzf6vECfNTnuI5BOlsEqzMYa9x1N9KPB5uJBzqVQrayOqZAO1ZUi58oHdsh8zB1qm63KwqOVASTkSH240kXgbBNSo44HSLu5dF/ltZbtK1KqVta1ZI3JE6CTNJ 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: List-Subscribe: List-Unsubscribe: On 2024/4/24 20:47, Nicolas Bouchinet wrote: > From: Nicolas Bouchinet > > Commit 284f17ac13fe ("mm/slub: handle bulk and single object freeing > separately") splits single and bulk object freeing in two functions > slab_free() and slab_free_bulk() which leads slab_free() to call > slab_free_hook() directly instead of slab_free_freelist_hook(). Right. > > If `init_on_free` is set, slab_free_hook() zeroes the object. > Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` are > set, the do_slab_free() slowpath executes freelist consistency > checks and try to decode a zeroed freepointer which leads to a > "Freepointer corrupt" detection in check_object(). IIUC, the "freepointer" can be checked on the free path only when it's outside the object memory. Here slab_free_hook() zeroed the freepointer and caused the problem. But why we should zero the memory outside the object_size? It seems more reasonable to only zero the object_size when init_on_free is set? Thanks. > > Object's freepointer thus needs to be properly set using > set_freepointer() after init_on_free. > > To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the > command line of a kernel build with `CONFIG_SLAB_FREELIST_HARDENED=y`. > > dmesg sample log: > [ 10.708715] ============================================================================= > [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): Freepointer corrupt > [ 10.712695] ----------------------------------------------------------------------------- > [ 10.712695] > [ 10.712695] Slab 0xffffd8bdc400d580 objects=32 used=4 fp=0xffff9d9a80356f80 flags=0x200000000000a00(workingset|slab|node=0|zone=2) > [ 10.716698] Object 0xffff9d9a80356600 @offset=1536 fp=0x7ee4f480ce0ecd7c > [ 10.716698] > [ 10.716698] Bytes b4 ffff9d9a803565f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.720703] Object ffff9d9a80356600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.720703] Object ffff9d9a80356610: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.724696] Padding ffff9d9a8035666c: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > [ 10.724696] Padding ffff9d9a8035667c: 00 00 00 00 .... > [ 10.724696] FIX kmalloc-rnd-05-32: Object at 0xffff9d9a80356600 not freed > > Signed-off-by: Nicolas Bouchinet > --- > mm/slub.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 3aa12b9b323d9..71dbff9ad8f17 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -4342,10 +4342,16 @@ static __fastpath_inline > void slab_free(struct kmem_cache *s, struct slab *slab, void *object, > unsigned long addr) > { > + bool init = false; > + > memcg_slab_free_hook(s, slab, &object, 1); > + init = slab_want_init_on_free(s); > > - if (likely(slab_free_hook(s, object, slab_want_init_on_free(s)))) > + if (likely(slab_free_hook(s, object, init))) { > + if (init) > + set_freepointer(s, object, NULL); > do_slab_free(s, slab, object, object, 1, addr); > + } > } > > static __fastpath_inline