From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A20BE470121; Wed, 23 Sep 2026 14:27:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790173666; cv=none; b=bSAbppZxIozjP7TKQ7Zj5hr5vQ9vo91U5vZckAWalMSGWTOrFw1M7pjvL4UZpcJCHjU7vbyQH7+pB5m3Mcbhv9oPylFwuTjzbFx4dsL4u50JstWnYi4lD7gaI2ZFnr+WBPWgk+lGbKeDDz06XpjSHdsDRmUA3SJevx/Qq5YN2Kc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790173666; c=relaxed/simple; bh=/KPB5pPtjG5kIy+f5e5YaahUYv3q6YKfwK/wmTxdl9Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bd9SFbmf/OS+LbI2o1Luy1U0MmbF9rkmX04H88adIxcmZ/6VzgVusrzjc04vh/Q2W6sTbcFf2HwWXMSXkcfl/J8uIrRFSROL98HK0lpO6uKxZGgA2B3vsKTnSxV6s/rEUbyBbAV2305/T8DKSPiLR6PBHHjzX9f9LVWgLTvVkdI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=aCdhtLJr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="aCdhtLJr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CDBE1F000FF; Wed, 23 Sep 2026 14:27:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790173665; bh=GrRsmntFvVUuadutjr8rWn+jflRGj/WKyZgDFRbE5D0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aCdhtLJrA7E0ZyMSqKPwond6XMnS2RXxHHAm0hmLoQgd4B4NW8MpXly/2UWgTY1gK ldsThpxtSkPuE9crHdikowa+PmBHaH3WP8DTlM5k7ozuFhrpqdjl/zYdU1EBu3HLV9 uS3piB7A/vUZi47+lVzQeU7irpkEvnx54FOr4Wos= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiayuan Chen , Shakeel Butt , Usama Arif , Dave Chinner , Johannes Weiner , Kairui Song , Muchun Song , Roman Gushchin , Andrew Morton Subject: [PATCH 7.2 317/438] mm/shrinker: fix bogus set_shrinker_bit() with cgroup.memory=nokmem Date: Wed, 23 Sep 2026 16:05:38 +0200 Message-ID: <20260923140653.009105876@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140644.756254324@linuxfoundation.org> References: <20260923140644.756254324@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen commit 932cfb25e7ce98d1f93895671ec186a3087e4f80 upstream. With cgroup.memory=nokmem, shrinker_memcg_alloc() bails out early and never allocates an id, so shrinker->id keeps the 0 it got from the kzalloc() in shrinker_alloc(). __list_lru_init() then copies that 0 into lru->shrinker_id, where it looks like a valid bit index. Nothing calls expand_shrinker_info() on nokmem either, so shrinker_nr_max stays 0 and every memcg ends up with an empty map (map_nr_max == 0). deferred_split_folio() hands a real memcg to __list_lru_add() regardless of whether the lru is memcg aware, so the first THP queued in a cgroup does set_shrinker_bit(memcg, nid, 0) and trips the bounds check: WARNING: mm/shrinker.c:212 at set_shrinker_bit+0x7d/0x90, CPU#126 Call Trace: deferred_split_folio+0x18c/0x220 map_anon_folio_pmd_nopf+0xdd/0x130 map_anon_folio_pmd_pf+0x14/0xb0 do_huge_pmd_anonymous_page+0x1a1/0x620 __handle_mm_fault+0xea9/0x10d0 handle_mm_fault+0xe5/0x320 do_user_addr_fault+0x1cc/0x870 exc_page_fault+0x81/0x1b0 asm_exc_page_fault+0x27/0x30 Harmless, the WARN_ON_ONCE() is what keeps the out of bounds unit[] read from happening, but the id should not look valid in the first place. Clear it before returning. Two other spots could paper over this: drop the id in __list_lru_init() when nokmem turns memcg_aware off, or make deferred_split_folio() pass NULL like list_lru_add_obj() does. Both leave shrinker->id lying around for the next caller, so fix it where the id is handed out. Link: https://lore.kernel.org/20260902073800.305481-1-jiayuan.chen@linux.dev Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") Signed-off-by: Jiayuan Chen Acked-by: Shakeel Butt Cc: Usama Arif Cc: Dave Chinner Cc: Johannes Weiner Cc: Kairui Song Cc: Muchun Song Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/shrinker.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/shrinker.c b/mm/shrinker.c index a70aab124a0e..7ec2a9704f6f 100644 --- a/mm/shrinker.c +++ b/mm/shrinker.c @@ -227,6 +227,8 @@ static int shrinker_memcg_alloc(struct shrinker *shrinker) { int id; + shrinker->id = -1; + if (mem_cgroup_disabled()) return -ENOSYS; if (mem_cgroup_kmem_disabled() && !(shrinker->flags & SHRINKER_NONSLAB)) -- 2.55.0