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 352C82FF641; Fri, 7 Aug 2026 14:47:54 +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=1786114075; cv=none; b=dnMffftmW8IUCGv5d8ER7rhFzNQJq9SQbXqnQWe4SOEoA9DxHwwBiV4IUSJp65mT8t/5x78psDW7p9HzWX23Jh7lsrevzO3iJ9lta7BoCmoBXY6neLIz7G9DPV/gr1HNdMrQk/vrRzzIkUY0Ld8BonHxR1/NwjZ32/owcOCt7qo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114075; c=relaxed/simple; bh=fGJ3RqUdQBqr+NzaBEzJz5/g/pg2orgv+xB7l6ALaZA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qKpB2lVpJr9xfXW1nACAZoO6ZlzQPzfWZKykCKze+uUGQGZO3fBYeah/vbY2q3fGPwLF4CEqCPQ94ekXyG8/+XI3Tmv3qcjumOMc4HXOfHUXNDWXB4A3qEffRdWHyuDK4VFbS+gHyLWwVIg2qyWzpO9Ue3I7SV2uObTmaNriue4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=L3c1IAiT; 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="L3c1IAiT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72E651F000E9; Fri, 7 Aug 2026 14:47:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786114074; bh=PHSjJ9/xn8QrzONMWf/8qc69soF3IOooATk1zVys2rE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=L3c1IAiTirfJLqA4yfYtOsCulEiB4B/eno+rZSk35afyOHtV4f1nM5KXiqvI+ZiAx ulJpziElr0VcJjCrwL2HxHt1+kuo6ODXoitHo+FCQEtmEOdnQjJPZZH3XWGb/TKby3 NXwH3rwFa3yeaHjnRhZlcY/bEKe0yKDkcToIWjm4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sashiko , Zi Yan , Dennis Zhou , Christoph Lameter , Tejun Heo , Andrew Morton Subject: [PATCH 6.12 136/337] mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk() Date: Fri, 7 Aug 2026 16:35:39 +0200 Message-ID: <20260807143421.482381261@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143418.516897842@linuxfoundation.org> References: <20260807143418.516897842@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zi Yan commit 89b1b79c308818a715e75f28744b70d8940a07c9 upstream. In pcpu_create_chunk(), nr_pages is the total contiguous backing allocation, i.e., nr_units * pcpu_unit_pages, but pcpu_chunk_populated() uses it to set chunk->populated, whose size is pcpu_unit_pages, bitmap. Since bit N in chunk->populated means page offset N inside every unit is backed. When nr_units > 1, the function writes beyond chunk->populated. Fix it by using chunk->nr_pages. It also fixes the global pcpu_nr_empty_pop_pages accounting, since pcpu_balance_free() only iterates up to chunk->nr_pages. Commit a63d4ac4ab609 ("percpu: make percpu-km set chunk->populated bitmap properly") introduced the bitmap overflow issue. Later, commit b539b87fed37f ("percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated") added pcpu_nr_empty_pop_pages and caused the accounting issue. Link: https://lore.kernel.org/20260709-fix-pcpu_create_chunk-in-percpu-km-v1-1-1f64745a84cc@nvidia.com Fixes: a63d4ac4ab609 ("percpu: make percpu-km set chunk->populated bitmap properly") Reported-by: Sashiko Closes: https://sashiko.dev/#/patchset/20260703-keep-subpage-private-zero-at-free-v2-0-2970fe777dd6%40nvidia.com?part=1 Assisted-by: Codex:GPT-5 Signed-off-by: Zi Yan Acked-by: Dennis Zhou Cc: Christoph Lameter Cc: Tejun Heo Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/percpu-km.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/percpu-km.c +++ b/mm/percpu-km.c @@ -75,7 +75,7 @@ static struct pcpu_chunk *pcpu_create_ch chunk->base_addr = page_address(pages); spin_lock_irqsave(&pcpu_lock, flags); - pcpu_chunk_populated(chunk, 0, nr_pages); + pcpu_chunk_populated(chunk, 0, chunk->nr_pages); spin_unlock_irqrestore(&pcpu_lock, flags); pcpu_stats_chunk_alloc();