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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4C5ABC44515 for ; Mon, 20 Jul 2026 06:58:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 566F96B0098; Mon, 20 Jul 2026 02:58:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 518616B0099; Mon, 20 Jul 2026 02:58:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 430E06B009B; Mon, 20 Jul 2026 02:58:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 20C606B0098 for ; Mon, 20 Jul 2026 02:58:58 -0400 (EDT) Received: from smtpin14.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 8DFEE4072D for ; Mon, 20 Jul 2026 06:58:57 +0000 (UTC) X-FDA: 85008252714.14.19BEC8F Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) by imf06.hostedemail.com (Postfix) with ESMTP id 23CB7180004 for ; Mon, 20 Jul 2026 06:58:53 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=jcy5LAak; spf=pass (imf06.hostedemail.com: domain of ye.liu@linux.dev designates 95.215.58.182 as permitted sender) smtp.mailfrom=ye.liu@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=1784530736; 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=jxcjZTfCxdOxrLMz+THGBCm+S/NYMN19qenWyxKwTqM=; b=LM/poWBRIjiyC4evYNzqxkvYVQPwVA7AqLGvBWCy6sLs2vNe3Mxj2YV1wTo9kj+WoHws3F nzK0M24Ig5NqH6oNN4Lyn72sO+i+WbBcerFCAhNsgkY+ffS0x81Onvu1SN05Pv0Fmps6PM pzVeh+uWg6H+Ox1I8jxybSGDdOpP9EM= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=jcy5LAak; spf=pass (imf06.hostedemail.com: domain of ye.liu@linux.dev designates 95.215.58.182 as permitted sender) smtp.mailfrom=ye.liu@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784530736; b=DOlj8Q3oaSwTZnopKqtCp6lxYZRLwzczwG83qt66EBQXbvdEjdhzO9awm7Hy6py+UMq0b8 U/BaqoUdcfNaoMK1p9aOO8vKlsGu1jvix/0AIstAzr8u9gfqkJtVfswby4CFBoBzE78sOI uXJZlFYOp5mAMJ2o3VqJu9G/ldJwIp4= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784530730; 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=jxcjZTfCxdOxrLMz+THGBCm+S/NYMN19qenWyxKwTqM=; b=jcy5LAakIaLoy8oknD7Y0v2vm4C3A1mefiHvg8tzak2qb0WXiuIrFWQ0eMqJ9mKF4hjUOe Zlk+gVEdVgha/pwINdIeLxXrrzJSKqDUiIZYljjy3mams7qqXSgljLf9oPG8/8iX8tjgml xkQ86I5SyPIA8zQr2gBJWsJHUoJWXeg= Date: Mon, 20 Jul 2026 14:58:10 +0800 MIME-Version: 1.0 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ye Liu Subject: Re: [PATCH v6 9/9] mm/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg() To: Andrew Morton Cc: "Vlastimil Babka (SUSE)" , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260714015117.78351-1-ye.liu@linux.dev> <20260714015117.78351-10-ye.liu@linux.dev> <21007313-40dc-46fb-bbf2-453c8eedf3e8@kernel.org> <20260719224255.8e2bc60e8a42681fb541e6ad@linux-foundation.org> Content-Language: en-US In-Reply-To: <20260719224255.8e2bc60e8a42681fb541e6ad@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 23CB7180004 X-Stat-Signature: rowjbqziqf1qwwqutkdbu5ykfqdrra4o X-HE-Tag: 1784530733-843812 X-HE-Meta: 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 EFjjNzAb 8bVv5q8GU5Qrh7wXH/xuFeDmGWUfeoaDs/byh3J0xrXkRELIJoLhIy29d0vKpg2E4XkG4bfCF91Dzy4zUuW9lmK2/1JzDQMk11ibTfz8G0tmGFBg/oZDMfIf/C9OleDiwgFZPvQPsoB3YqBwRiwJMUGN7026o1DKS/9K5fSh3jW8MMYbAsFiXVBq9HpZegTjrx3E3vP4JOs0aS8zAgvKGK3kNMaErD7545Fsf3sxCxB2RiEtlARQyk9wgzUfBr9JOGcfRtwUt8Q4+C/nSolRkRdyMLuGF/UH6kNQeCKCEtM0bRWzrWKfuwOBWkCn5GdIxIr4F8xVhnpgKw9UWcwrPWcTVa/42oYAjoD6/i5sIVVeTmTTlfKqxAlutOan9gbZ4ikvUvcAYKVCXKcsjqiVJrKcWugBAJ7Stt2CeFQW+98wIVAywwxNc8IkjmeXhOOLDW4zTMkk8L5mIxDgYtIA/3LlTiA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/7/20 13:42, Andrew Morton 写道: > On Mon, 20 Jul 2026 10:45:56 +0800 Ye Liu wrote: > >>> These points have too much detail that's already in the code. Would just >>> mention that we opencode applicable parts of page_memcg_check() and >>> PageMemcgKmem() using the snapshot? >> Yes,It's a bit wordy. >>> >>>> This avoids both TOCTOU windows and the assertions entirely. >>>> >>>> Signed-off-by: Ye Liu >>> >>> Reviewed-by: Vlastimil Babka (SUSE) >>> >>> Was all of this reported by sashiko? At least the new-in-v6 was? >>> Then: >>> >>> Reported-by: Sashiko >>> >>> But it's no longer a cleanup but a fix, so probably this? >>> >>> Fixes: fcf8935832b8 ("mm/page_owner: print memcg information") >>> Cc: stable@vger.kernel.org >>> >>> It's not fixing a new regression so I think it's fine to keep it part of >>> this series for next release and not need to split out for mm-hotfixes. >>> >> Hi Andrew, >> >> Could you please help me revise the above? > > Sure, how does this look? > Looks great, thank you! > > From: Ye Liu > Subject: mm/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg() > Date: Tue, 14 Jul 2026 09:51:08 +0800 > > print_page_owner_memcg() reads page->memcg_data via READ_ONCE() at the > start to guard against tail pages and NULL data. However, it later > re-reads page->memcg_data locklessly in two places: > > 1: page_memcg_check(page) > > 2: PageMemcgKmem(page) (via folio_memcg_kmem(), which includes > VM_BUG_ON assertions for tail pages and MEMCG_DATA_OBJEXTS) > > If the page is concurrently freed and reallocated as a THP tail page or > slab page between these calls, the VM_BUG_ON assertions can trigger on > CONFIG_DEBUG_VM=y builds, crashing the kernel. > > Fix both TOCTOU issues by using the memcg_data snapshot throughout. > > Link: https://lore.kernel.org/20260714015117.78351-10-ye.liu@linux.dev > Fixes: fcf8935832b8 ("mm/page_owner: print memcg information") > Signed-off-by: Ye Liu > Reviewed-by: Zi Yan > Reviewed-by: Vlastimil Babka (SUSE) > Cc: Brendan Jackman > Cc: Johannes Weiner > Cc: Lorenzo Stoakes > Cc: Michal Hocko > Cc: Suren Baghdasaryan > Cc: David Hildenbrand (Arm) > Cc: -- Thanks, Ye Liu