From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-127.mta1.migadu.com [95.215.58.127]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5F2D8381E83 for ; Fri, 4 Sep 2026 07:15:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.127 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788506110; cv=none; b=R1tkex8jQAl33LNl8Nn/IjyIALDMDKDcob5t2KkJ3eVRLUalnTdU/4ffNfQV21HgBKWHMWZV808DXiARWLxLd4RPIU8isWB+sRRyJAHyhYoxRlXP6LAbwo67ywZCH58aWOh5jVhueac6AIwBmvpvYGER/AtrCTEV7Vy+dWTd5aQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788506110; c=relaxed/simple; bh=g6KBlsEfdQ6twWTWJN7KP2LWVnATn4EXLmzlK1fULfQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=X4KCU8EEPqWvHy2dXBMxv23+ZcjrXRKdeYiTNiZkYNgcUzYI3MDRplv4vNG8SYJOEMvIfAZLLc7gyyNDK34tRlPjqGZrSEc8TcU0RSbm3VUW97VDiNwD0F3uMneGgaWg1rCxC3I/0PD9Nc0OTUiEISq2Wzjw2JFDblxF3eEBvBo= 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=SmcwlpbM; arc=none smtp.client-ip=95.215.58.127 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="SmcwlpbM" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=g6KBlsEfdQ6twWTWJN7KP2LWVnATn4EXLmzlK1fULfQ=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788506105; v=1; x=1789110905; b=SmcwlpbM66DwGbZwAGp5WX54XzlYShr8QdRDVJ/CTl2r044ow6DG5aMQ7Skoetyd/WB1KzWT mKvH0gqiHSLFaRDpJRf9jT7MRJZpn1crzKYFQ+OmtxJgXxrynvdXkflVwYmBb3lo71X9DsTP7p2 pjubpg3vDhxhY338VPiAKYtc= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 90fa9b6c7ea8f2ef; Fri, 04 Sep 2026 07:14:55 +0000 X-Mizu-Trace-ID: 90fa9b6c7ea8f2ef X-Migadu-Flow: FLOW_OUT From: Tao Cui To: axboe@kernel.dk, Tang Yizhou , Bart Van Assche Cc: tj@kernel.org, josef@toxicpanda.com, boris@bur.io, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, cuitao@kylinos.cn, cui.tao@linux.dev, Tang Yizhou Subject: [PATCH v2] blk-cgroup: avoid 32-bit overflow in root io.stat byte accounting Date: Fri, 4 Sep 2026 15:14:43 +0800 Message-ID: <20260904071443.1283147-1-cui.tao@linux.dev> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Bart Van Assche Reviewed-by: Tang Yizhou --- Changes in v2: - Rebase onto current linux-next head (no code change). - Add the Reviewed-by tags collected on v1 (Bart Van Assche, Tang Yizhou). - Link to v1: https://lore.kernel.org/r/20260714063118.1153083-1-cui.tao@linux.dev --- 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 2b5c29434e42..471cfd2347c9 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1118,11 +1118,11 @@ 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