From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from va-2-40.ptr.blmpb.com (va-2-40.ptr.blmpb.com [209.127.231.40]) (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 D9E4C397321 for ; Sat, 27 Jun 2026 10:55:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.127.231.40 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782557750; cv=none; b=X92GB+YNPXB2X6k1A3HFYlseLgJ5Jif4OnHu2jy5lId/xa9JB65W3SjfILnqIN1NC8QZ4KqesYy6oOnp/oGDEpdjywoBA4YCatX8kYcRurYWoLYe+S1nXePBsfdg5ZwqFMY9H8tdmwd9a+3se4vKciBj342fjZmqp+2+gJBhECc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782557750; c=relaxed/simple; bh=vtGATUPt86WF7+/0EE9gcOnC9h9VC94AN2kCl56wzEY=; h=From:Date:Cc:Subject:Mime-Version:Content-Type:To:Message-Id; b=QjqfApbA2dG68YtFvkfvWUdolFucOhHyqcW3Pm/Doznem9LS6fxIBFnqsdGlMguUVg3/tz5DHnNmsWBILsip6XuIRps06UDIf429Ej1nKJEd418UQftb0QgHpaOfHDZvD9ammqAP4HM6kU4jMqEYW88L74U/1vKNzwQmPFfNmtc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=fnnas.com; spf=none smtp.mailfrom=fnnas.com; dkim=pass (2048-bit key) header.d=fnnas-com.20200927.dkim.feishu.cn header.i=@fnnas-com.20200927.dkim.feishu.cn header.b=hpiqlpyO; arc=none smtp.client-ip=209.127.231.40 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=fnnas.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=fnnas.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fnnas-com.20200927.dkim.feishu.cn header.i=@fnnas-com.20200927.dkim.feishu.cn header.b="hpiqlpyO" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=s1; d=fnnas-com.20200927.dkim.feishu.cn; t=1782557736; h=from:subject:mime-version:from:date:message-id:subject:to:cc: reply-to:content-type:mime-version:in-reply-to:message-id; bh=09NI9h8pXOVJePy8ekMkP/0ApeXcwji/+//+YNUsm50=; b=hpiqlpyOCUXjO9Y6CVr9iVeGgUlZyvETHTUA2gsbFHKL7zuGvHW7y5gN9Q20j5HJdCRkCS +E7fRMlSHYeDZf8Nh3hrzH9CuThugIK6xkG1hD/H7oPj1CAWWQtdjqDRLt32slftgULZEn PMnQb8DJx4TXHTuv1bRdfsiqYx6hh3+BFk9m9mBI3ukkf0V8nffZkeJK0SJ0M5LCxhcRjw 1sxwjDzvlh8e1FILEbIXnsGn1Y8uYJddP5grT3/8N+QBIxTeEUCH20IKaTP+SZBPPx/rJI e8jM5I2ptZP8d3UqbybigSwbiYKnYtiPmyp4j0bSNkj+XK6yssvo4CQdtsmIGg== X-Original-From: chencheng@fnnas.com Received: from fedora ([27.47.238.101]) by smtp.feishu.cn with ESMTPS; Sat, 27 Jun 2026 18:55:34 +0800 X-Mailer: git-send-email 2.54.0 From: "Chen Cheng" Date: Sat, 27 Jun 2026 18:55:23 +0800 Content-Transfer-Encoding: 7bit Cc: , Subject: [PATCH] md/raid5: protect lockless reshape_progress accesses Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: , Message-Id: <20260627105524.144022-1-chencheng@fnnas.com> X-Lms-Return-Path: From: Chen Cheng During reshape: - reshape_request() advances conf->reshape_progress. - reshape_request() itself also reads conf->reshape_progress several times while calculating sector_nr, writepos, and readpos for the current reshape step. - use_new_offset() reads conf->reshape_progress locklessly to decide whether the current stripe should use data_offset or new_data_offset. one possible scenario is: CPU1 CPU2 reshape_request() -> conf->reshape_progress += delta ops_run_io() -> use_new_offset(conf, sh) -> progress = conf->reshape_progress -> decide old layout or new layout -> use data_offset or new_data_offset reshape_progress is the boundary between old and new layout mapping. If CPU2 observes an unprotected reshape_progress value, it can choose the wrong layout offset for the current stripe. if reshape_request() reads reshape_progress multiple times without a stable snapshot, one iteration of reshape can calculate its range from inconsistent progress values. Fixes: 7a6613810785 ("md/raid5: reshape using largest of old and new chunk size") The race report: ================================================================== BUG: KCSAN: data-race in ops_run_io / reshape_request write to 0xffff89a8d3ef2270 of 8 bytes by task 1299 on cpu 7: reshape_request+0x1292/0x17b0 raid5_sync_request+0x815/0xa00 md_do_sync.cold+0xf8d/0x1516 md_thread+0x15a/0x2d0 [....] read to 0xffff89a8d3ef2270 of 8 bytes by task 1292 on cpu 9: ops_run_io+0xc25/0x1960 handle_stripe+0x2273/0x4570 handle_active_stripes.isra.0+0x6e0/0xa50 raid5d+0x7d5/0xb90 [....] value changed: 0x0000000000173700 -> 0x0000000000173800 ================================================================== Signed-off-by: Chen Cheng --- drivers/md/raid5.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index eaee7f206ab8..b6809f1a3ab4 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -1011,11 +1011,11 @@ static void stripe_add_to_batch_list(struct r5conf *conf, /* Determine if 'data_offset' or 'new_data_offset' should be used * in this stripe_head. */ static int use_new_offset(struct r5conf *conf, struct stripe_head *sh) { - sector_t progress = conf->reshape_progress; + sector_t progress = READ_ONCE(conf->reshape_progress); /* Need a memory barrier to make sure we see the value * of conf->generation, or ->data_offset that was set before * reshape_progress was updated. */ smp_rmb(); @@ -6340,24 +6340,25 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk sector_t writepos, readpos, safepos; sector_t stripe_addr; int reshape_sectors; struct list_head stripes; sector_t retn; + sector_t reshape_progress = READ_ONCE(conf->reshape_progress); if (sector_nr == 0) { /* If restarting in the middle, skip the initial sectors */ if (mddev->reshape_backwards && - conf->reshape_progress < raid5_size(mddev, 0, 0)) { + reshape_progress < raid5_size(mddev, 0, 0)) { sector_nr = raid5_size(mddev, 0, 0) - - conf->reshape_progress; + - reshape_progress; } else if (mddev->reshape_backwards && - conf->reshape_progress == MaxSector) { + reshape_progress == MaxSector) { /* shouldn't happen, but just in case, finish up.*/ sector_nr = MaxSector; } else if (!mddev->reshape_backwards && - conf->reshape_progress > 0) - sector_nr = conf->reshape_progress; + reshape_progress > 0) + sector_nr = reshape_progress; sector_div(sector_nr, new_data_disks); if (sector_nr) { mddev->curr_resync_completed = sector_nr; sysfs_notify_dirent_safe(mddev->sysfs_completed); *skipped = 1; @@ -6377,13 +6378,13 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk * the data about to be copied would over-write the source of * the data at the front of the range. i.e. one new_stripe * along from reshape_progress new_maps to after where * reshape_safe old_maps to */ - writepos = conf->reshape_progress; + writepos = reshape_progress; sector_div(writepos, new_data_disks); - readpos = conf->reshape_progress; + readpos = reshape_progress; sector_div(readpos, data_disks); safepos = conf->reshape_safe; sector_div(safepos, data_disks); if (mddev->reshape_backwards) { if (WARN_ON(writepos < reshape_sectors)) @@ -6404,11 +6405,11 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk /* Having calculated the 'writepos' possibly use it * to set 'stripe_addr' which is where we will write to. */ if (mddev->reshape_backwards) { - if (WARN_ON(conf->reshape_progress == 0)) + if (WARN_ON(reshape_progress == 0)) return MaxSector; stripe_addr = writepos; if (WARN_ON((mddev->dev_sectors & ~((sector_t)reshape_sectors - 1)) - @@ -6514,14 +6515,21 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk set_bit(STRIPE_HANDLE, &sh->state); } list_add(&sh->lru, &stripes); } spin_lock_irq(&conf->device_lock); - if (mddev->reshape_backwards) - conf->reshape_progress -= reshape_sectors * new_data_disks; - else - conf->reshape_progress += reshape_sectors * new_data_disks; + if (mddev->reshape_backwards) { + sector_t progress = conf->reshape_progress; + + progress -= reshape_sectors * new_data_disks; + WRITE_ONCE(conf->reshape_progress, progress); + } else { + sector_t progress = conf->reshape_progress; + + progress += reshape_sectors * new_data_disks; + WRITE_ONCE(conf->reshape_progress, progress); + } spin_unlock_irq(&conf->device_lock); /* Ok, those stripe are ready. We can start scheduling * reads on the source stripes. * The source stripes are determined by mapping the first and last * block on the destination stripes. -- 2.54.0