From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (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 490953DA7E6 for ; Tue, 14 Jul 2026 06:31:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784010709; cv=none; b=W8IC3mTZljejb1ewAy0a6QLjjlyidZ/jRC2t0xeAKDpabaOBffJLKBCzzea5LtuIGxQqh41ZB80Gdxa4duiI6VrhmKthm13/jikfgQCfixzGmamI1eF2rk3wGoyZro37/hzVwzQwmAMARAeHQRktGkGRVD78rHlxb7HvfaYFWL4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784010709; c=relaxed/simple; bh=p7ZGe7ovr6Fnp+xJqMj+SXZ7ZkuYYQUS1ExBdGpuXYI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=DTCz2dF8UusOehne4mjxZxeAC9japz8mrMOEZ0pZCIsdXwXYMVS8a5eBOCIpxJzjkq5JgeR5wFbSZzAlYmtjVsQM2+rwO411Pv1LuJAVk/udBY6T6/8tceZwe/rLrhGxKd1CXcR+gSzDIonbRUy5GUwfTm7L0gf/ZtY7W8nE0AY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=GEebQZjY; arc=none smtp.client-ip=91.218.175.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="GEebQZjY" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784010695; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=uX8GOm2Y6bu+4/Uc+uJ+m9Biszo7L7ChblxvTzcX6kg=; b=GEebQZjY+R6uOyuJp7bWgNjQdi6sRvq8r8FRuB5PiK0T4/+6hvADZQwQMB35XC8NKuM0G3 eMdUfx6zGrD32Hhx0eWlZJTUOyh1DGvjzQBJr1QmBIsy233DvAt8MWPji+NE1nHBxuBju7 a5qfj8/OCFZ9xpvdnxu/7Wp/uXvNczk= From: Tao Cui To: axboe@kernel.dk Cc: tj@kernel.org, josef@toxicpanda.com, boris@bur.io, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Tao Cui Subject: [PATCH] blk-cgroup: avoid 32-bit overflow in root io.stat byte accounting Date: Tue, 14 Jul 2026 14:31:18 +0800 Message-ID: <20260714063118.1153083-1-cui.tao@linux.dev> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Tao Cui blkcg_fill_root_iostats() converts per-CPU sector counts to bytes with tmp.bytes[BLKG_IOSTAT_READ] += cpu_dkstats->sectors[STAT_READ] << 9; but disk_stats.sectors is `unsigned long`, and the shift is carried out in that type before the result is promoted to the u64 accumulator. On 32-bit kernels (unsigned long is 32 bits) this wraps, so once a per-CPU counter reaches 2**23 sectors (~4 GiB) the computed byte count is wrong, corrupting the root cgroup's io.stat. Every other sector->byte conversion in the tree casts to a wide type first ((loff_t)sectors << SECTOR_SHIFT in bdev.c, (u64)max_sectors << SECTOR_SHIFT in blk-settings.c); do the same here. Fixes: ef45fe470e1e5 ("blk-cgroup: show global disk stats in root cgroup io.stat") Signed-off-by: Tao Cui --- block/blk-cgroup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index d2a1f5903f24..a778aa9d2bb9 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1112,11 +1112,11 @@ static void blkcg_fill_root_iostats(void) cpu_dkstats->ios[STAT_DISCARD]; // convert sectors to bytes tmp.bytes[BLKG_IOSTAT_READ] += - cpu_dkstats->sectors[STAT_READ] << 9; + (u64)cpu_dkstats->sectors[STAT_READ] << SECTOR_SHIFT; tmp.bytes[BLKG_IOSTAT_WRITE] += - cpu_dkstats->sectors[STAT_WRITE] << 9; + (u64)cpu_dkstats->sectors[STAT_WRITE] << SECTOR_SHIFT; tmp.bytes[BLKG_IOSTAT_DISCARD] += - cpu_dkstats->sectors[STAT_DISCARD] << 9; + (u64)cpu_dkstats->sectors[STAT_DISCARD] << SECTOR_SHIFT; } flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync); -- 2.43.0