From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id EA1A9606A31E for ; Sat, 31 Oct 2026 09:42:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=SlvOoo7h Received: by kanga.kvack.org (Postfix) id C08026B05C5; Sat, 31 Oct 2026 05:42:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BDF006B05C6; Sat, 31 Oct 2026 05:42:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AF5656B05C7; Sat, 31 Oct 2026 05:42:54 -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 6F5406B05C5 for ; Sat, 31 Oct 2026 05:42:54 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id DD3911C42D1 for ; Sat, 31 Oct 2026 09:42:53 +0000 (UTC) X-FDA: 85382432226.11.F96C6DF Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf14.hostedemail.com (Postfix) with ESMTP id 1D5F2100003 for ; Sat, 31 Oct 2026 09:42:51 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=SlvOoo7h; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793439772; 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=l+l7vL6OppC3xXbuZ+6FYNU9AQPqNjHig+EtP/8oH5c=; b=paeoGvGGJsjpL7Hxr76cKOtHPAN+v0fooIdwsGkVCUZpAB3fYBo1o+KRYTZwh1vTyr1XZv JvOezrffo9Pe2Bu1rBQLbQoXgJ0IC7UV8RTJJIoResbwDMUNcdAhA9OoLZAVRGDWwgMv3z mMH+oVb4AejJJlYQ7oZlCEgCw6o0FHQ= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=SlvOoo7h; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793439772; b=gnKNCd/EbkLEtIllhJ9JyQzN6QTOd9qA6sWT4eyCI3lzkJS9Ns1wqtkPoa4se2b/+D9Cj6 YqJ+lwlWYQCl2IfydCWocbkSeNCX7QP6GRdeaECVYqRlYYJ4iGbiMEC40wkhWLv6h/JZSj DF8XRiu5Kwg/WPPHFub40mJL3OOY+AM= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 5D62842A93; Sat, 31 Oct 2026 09:42:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E61F31F00A1A; Sat, 31 Oct 2026 09:42:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439771; bh=l+l7vL6OppC3xXbuZ+6FYNU9AQPqNjHig+EtP/8oH5c=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=SlvOoo7h2NrGSce+EZ0r/TEXEBd2b3M+W3a5ZrbTwYZjlGRtxW/0dAR4JP4GA+76w P+f7bAuUNu1Yv1g1H7D8kFS4QD5s2CZBGegKhPNpITqlN7Ip3qbNZ4cy/WVa1ZlmjD /D2MxgtNqIQyQIzKHKj7qIVDjMAvkJf4rRPteq1rzuV+/rMCJ7D7uysNhe47S8OYi0 hM/g0ow18Z8BSkDidvpS/QUBtepf7GfsSShe5dLagt+hSjgLUsSJX9zgTlj9tPN+J/ 0X8jIEgDjVqkM1UbZ87/UjTXIQyGyjjTepCGPRDVpmowDIpCv4zaqmYY0OHgBX6iW2 qTDUniZzh/0Ww== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:39 +0100 Subject: [PATCH v3 10/47] mm/huge_memory: fix list corruption when deferred_split_scan() races with deferred_split_folio() X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-10-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Josef Bacik , Mani Tofigh , Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3706; i=david@kernel.org; h=from:subject:message-id; bh=JLLChxKIypxsdt4WbVQ02kyFhDQ6FU9NlTqVcswW/5U=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk8TMZnE9X4D4/OEzCXBE1Z9d/jC1rw4beqiza7Gr ftD/0+x6ihlYRDjYJAVU2QJCr5v8PLlutpqNz5mmDmsTCBDGLg4BWAitXmMDDuD94idilyy2OlJ +uw7ca5Hak9PM5FUNfP55rpY7WLg7Z0M/9NvzDOcl7v+Y92qeT0exhK3v3ycJN1/VN6Lyeh+8ln l97wA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Queue-Id: 1D5F2100003 X-Stat-Signature: 6rubkw45h1x3oun7s93cbo6wnu69a965 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1793439771-559849 X-HE-Meta: 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 vkTkXwGX 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Since the deferred split queue became a list_lru, the isolate callback moves the folios it took a reference on to an on-stack list, linked through folio->_deferred_list, and deferred_split_scan() takes them off that list with list_del_init() without holding the list_lru lock. deferred_split_folio() does not know about the on-stack list. It only holds the list_lru lock when it looks at the same list_head, and it can run for such a folio: a THP is queued when it is mapped, as a candidate for the underused check, and is queued "again" when a part of it gets unmapped: CPU0 deferred_split_scan() CPU1 deferred_split_folio() list_del_init(&folio->_deferred_list) next->prev = prev prev->next = next entry->next = entry list_lru_lock_irqsave() folio_set_partially_mapped() __list_lru_add() list_empty(item) -> true list_add_tail(item, &l->list) item->next = &l->list item->prev = tail entry->prev = entry The folio now sits on the list_lru with ->prev pointing to itself. The next removal leaves the neighbours pointing to it, and they still do so after the folio has been freed. With CONFIG_DEBUG_LIST: list_del corruption. prev->next should be ffd4000000270090, but was ffd4000000278090. (prev=ffd4000000270090) Fix it by grabbing the lock around list_del_init() so deferred_split_folio() cannot race with it. Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Johannes Weiner Reviewed-by: Mani Tofigh Tested-by: Mani Tofigh Reviewed-by: Lance Yang Tested-by: Muhammad Usama Anjum Signed-off-by: David Hildenbrand (Arm) --- mm/huge_memory.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index bd44d58e86845..4c0194af9016d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -4522,8 +4522,7 @@ int split_folio_to_list(struct folio *folio, struct list_head *list) * * It is unsafe to call folio_unqueue_deferred_split() until folio refcount is * zero: because even when the list_lru lock is held, a non-empty - * _deferred_list might be in use on deferred_split_scan()'s unlocked - * on-stack list. + * _deferred_list might be in use on deferred_split_scan()'s on-stack list. * * The list_lru sublist is determined by folio's memcg: it is therefore * important to unqueue deferred split before changing folio memcg. @@ -4665,10 +4664,22 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, deferred_split_isolate, &dispose); list_for_each_entry_safe(folio, next, &dispose, _deferred_list) { + struct mem_cgroup *memcg; + struct list_lru_one *lru; bool did_split = false; bool underused = false; + /* + * Sync with deferred_split_folio(), which can requeue the + * folio once list_empty() is true, and sets PG_partially_mapped. + */ + rcu_read_lock(); + memcg = folio_memcg(folio); + lru = list_lru_lock_irq(&deferred_split_lru, folio_nid(folio), + &memcg); list_del_init(&folio->_deferred_list); + list_lru_unlock_irq(lru); + rcu_read_unlock(); if (!folio_test_partially_mapped(folio)) { /* -- 2.43.0