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 E91BBC4828D for ; Tue, 6 Feb 2024 18:51:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4F7D26B0074; Tue, 6 Feb 2024 13:51:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4A7DC6B0078; Tue, 6 Feb 2024 13:51:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 36FB46B007D; Tue, 6 Feb 2024 13:51:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 286C66B0074 for ; Tue, 6 Feb 2024 13:51:51 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id E93E81A0382 for ; Tue, 6 Feb 2024 18:51:50 +0000 (UTC) X-FDA: 81762273180.14.AE06B28 Received: from mail-ej1-f53.google.com (mail-ej1-f53.google.com [209.85.218.53]) by imf11.hostedemail.com (Postfix) with ESMTP id B380340012 for ; Tue, 6 Feb 2024 18:51:48 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=cmpxchg-org.20230601.gappssmtp.com header.s=20230601 header.b=pSqPYc8R; dmarc=pass (policy=none) header.from=cmpxchg.org; spf=pass (imf11.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.218.53 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707245509; 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=621piEzSXJxB1zy3OuwwYQSE5VTqKJoLX8Sk8RtyImg=; b=Iq5Z7Dpetvp7uHhkdGgfZibEkrgsbrmJumnPjrIuv741cOy6idABHx2Xp+90PrQQBpaZmn /1KuWLuZRwwajcUXBD+UTMspDrReTGL7OydVd1FLuC8zXx4owg43veLHJ6LKcrHrj2P2Cp 06Wq7zKv91FLp8f+MQFrF3rUzQ/VgQs= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=cmpxchg-org.20230601.gappssmtp.com header.s=20230601 header.b=pSqPYc8R; dmarc=pass (policy=none) header.from=cmpxchg.org; spf=pass (imf11.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.218.53 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707245509; a=rsa-sha256; cv=none; b=ZX93/cCxqv04t4cXPEITQlkoOFn1A0S8FQn+w4cb7mIAaLkl9vtOZxdO+tEEyuz5WtvA1O WOERIY4m5FtuC1yU7YFzpAGj3Y0PTk9uxLQHN8HWGXTSj2fRq/e9OgT1bwFq/qR9D0RTfd 7FZ6RDkAVhua8xQDTS5WFX/nAvdgE/c= Received: by mail-ej1-f53.google.com with SMTP id a640c23a62f3a-a354fc17f24so691823566b.0 for ; Tue, 06 Feb 2024 10:51:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20230601.gappssmtp.com; s=20230601; t=1707245507; x=1707850307; darn=kvack.org; 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=621piEzSXJxB1zy3OuwwYQSE5VTqKJoLX8Sk8RtyImg=; b=pSqPYc8R1V9YelIU+nDl7p0aQc1mA0nqUwrSdTxyFf1iHObOLW0EpwPVMIE78N3nt/ 2w4uogzLEf0VAEqQJQ1+EIu/ktCOruvQRGKWjAdYTrKcpyZ3cK8AzMItyK11o5B09tZF mNBk1nM5jnnKXhdLyMpg6+VUw7r0P/EHkx3dVnvx39GoO9i1YLLBca84WUJ8hpSUl/Fb rxLez6cvpRG0MUZyXXSGAJiUwrVDncQtOKVi50npw/j5nGd0SneoWdxKMokRZNvr0YZG f2jzJ/8fAPLeO2WJXK+w0wV6il43T78IPA5y+m3uw/kUExHEQtNQX8r1gaOjTrz6ybHA +OkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707245507; x=1707850307; 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=621piEzSXJxB1zy3OuwwYQSE5VTqKJoLX8Sk8RtyImg=; b=H8F5Xk/lfkk1+3z1iy5R6G4zvZLzz7QzU/mmkryMj/XU/B77kXS1vuE3tJ8CnC1bRa qg00PC1WCjEOo34fDTb3NpkYHldRYpdMCae6B283ggtB8OCIR/KK1I6Np7KdCU91qgkc AjO+y9VKnBAjgCF5pByjZT7toVnnC2EMPSYn4MoNjvJFzzFDz3AbiajtxuaegKuyraRl 3ftm8kXIyYIkHbGD6rmKnBeeCoZ865HsJd5rCfMVtPKe7pgI8vosM7MDvUFqbLVEygCk OPnjI33tdc+esenDzezdhBpu5NtC4MmO+vxy/cLre1eOOWB/0vFM/hF447wGPK9koHrc PWQQ== X-Gm-Message-State: AOJu0YzmeukCuz5TpoRfRpE9UNGYqz5rUT1HZIe1yVji2My6TLhNPZDY 5+wbanaz++39uNrxonyvbUc9zNJIQirNftXv5ib7dfZJAhAYmAua9zEHu2OQahI= X-Google-Smtp-Source: AGHT+IFxYTbMcukoiLJjcgtMqQP0qNMxgZcZgHZ9EB6ONAVjWA5ZIv/bY2lcMFyv4EZnoA07trkBcQ== X-Received: by 2002:a17:906:f203:b0:a38:4f52:cd01 with SMTP id gt3-20020a170906f20300b00a384f52cd01mr796877ejb.53.1707245507031; Tue, 06 Feb 2024 10:51:47 -0800 (PST) X-Forwarded-Encrypted: i=0; AJvYcCXonRSCCIY5Y4O6Xfex2VBrnEbn2ZuvPgDRBBu5e4QaWvVzzQ8xMfROH4BNF5caLsLivrybO1kKOvzFl3rzflZrIs+Vh1AeHerZzHq5UMt/VT+XVkXSqYLpnjJSQ0mLpj6eZbOFG0U3Vh6kpQiPn5hKmPgDX032o1+Y4g2vNIZetwUFDpPkZwmgn0+KATokEp5b/ZFQf1yx02qWOCNmMSPOJdtySva6qg== Received: from localhost ([2620:10d:c092:400::5:310]) by smtp.gmail.com with ESMTPSA id tj10-20020a170907c24a00b00a354a5d2c39sm1448273ejc.31.2024.02.06.10.51.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Feb 2024 10:51:46 -0800 (PST) Date: Tue, 6 Feb 2024 19:51:45 +0100 From: Johannes Weiner To: Nhat Pham Cc: akpm@linux-foundation.org, chengming.zhou@linux.dev, yosryahmed@google.com, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/swap_state: update zswap LRU's protection range with the folio locked Message-ID: <20240206185145.GA97483@cmpxchg.org> References: <20240206180855.3987204-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240206180855.3987204-1-nphamcs@gmail.com> X-Rspamd-Queue-Id: B380340012 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 4yfyd4exfnecjq88bywpcrjoyeen6prk X-HE-Tag: 1707245508-141304 X-HE-Meta: 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 VTMIRyVA 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002824, 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 Tue, Feb 06, 2024 at 10:08:55AM -0800, Nhat Pham wrote: > When a folio is swapped in, the protection size of the corresponding > zswap LRU is incremented, so that the zswap shrinker is more > conservative with its reclaiming action. This field is embedded within > the struct lruvec, so updating it requires looking up the folio's memcg > and lruvec. However, currently this lookup can happen after the folio is > unlocked, for instance if a new folio is allocated, and > swap_read_folio() unlocks the folio before returning. In this scenario, > there is no stability guarantee for the binding between a folio and its > memcg and lruvec: > > * A folio's memcg and lruvec can be freed between the lookup and the > update, leading to a UAF. > * Folio migration can clear the now-unlocked folio's memcg_data, which > directs the zswap LRU protection size update towards the root memcg > instead of the original memcg. This was recently picked up by the > syzbot thanks to a warning in the inlined folio_lruvec() call. > > Move the zswap LRU protection range update above the swap_read_folio() > call, and only when a new page is allocated, to prevent this. > > Reported-by: syzbot+17a611d10af7d18a7092@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/000000000000ae47f90610803260@google.com/ > Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure") > Signed-off-by: Nhat Pham Looks great, thanks for updating it! One more thing I just realized: > --- > mm/swap_state.c | 10 ++++++---- > mm/zswap.c | 1 + > 2 files changed, 7 insertions(+), 4 deletions(-) > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index e671266ad772..7255c01a1e4e 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -680,9 +680,10 @@ struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, > /* The page was likely read above, so no need for plugging here */ > folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx, > &page_allocated, false); > - if (unlikely(page_allocated)) > + if (unlikely(page_allocated)) { > + zswap_folio_swapin(folio); > swap_read_folio(folio, false, NULL); > - zswap_folio_swapin(folio); > + } > return folio; > } > > @@ -855,9 +856,10 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask, > /* The folio was likely read above, so no need for plugging here */ > folio = __read_swap_cache_async(targ_entry, gfp_mask, mpol, targ_ilx, > &page_allocated, false); > - if (unlikely(page_allocated)) > + if (unlikely(page_allocated)) { > + zswap_folio_swapin(folio); > swap_read_folio(folio, false, NULL); > - zswap_folio_swapin(folio); > + } > return folio; > } > > diff --git a/mm/zswap.c b/mm/zswap.c > index 4aea03285532..8c548f73d52e 100644 > --- a/mm/zswap.c > +++ b/mm/zswap.c > @@ -827,6 +827,7 @@ void zswap_folio_swapin(struct folio *folio) > struct lruvec *lruvec; > > if (folio) { > + VM_WARN_ON_ONCE(!folio_test_locked(folio)); > lruvec = folio_lruvec(folio); > atomic_long_inc(&lruvec->zswap_lruvec_state.nr_zswap_protected); > } The NULL check is now also no longer necessary. It used to be called unconditionally, even if __read_swap_cache_async() failed and returned NULL. However, page_allocated == true implies success. That newly allocated and locked folio is always returned.