From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f178.google.com (mail-oi1-f178.google.com [209.85.167.178]) (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 5028F181B9F for ; Wed, 12 Jun 2024 16:54:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718211276; cv=none; b=KPCizDQ6IydoSQTOavmcfqXwN0rCe/bngVoTS3RNnlKBzQF10Ostvf2P2cq/RL4kcJsUPASm2TsMVsit+SXdQwNxRt44z91cntiWIoV/CTft1pQDTpokj5Je2VNLKizb6VHwo2059YQ8hfvsNJUh7/hP8F/1qhZ2XoEtLJpPjwk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718211276; c=relaxed/simple; bh=1thz6tnKYh4W3UTSkm0UIqpLg3cHhFT9lD2SEIdOi/Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=R+vfUqxO+mIgnagYAzVzyd6OlUUCJ3txhxG5YEtrSEWRra5YbZBb8pw9bLZHS1Tc4RGtk4b8WrJ89yyry9/UdhiqcN38wsaCSR1W+9qBdDkFFm9wet81V2XGx/hJBqn5FXite1atKR367cXLfDouTk+UhKnfeKpN7wb+llcsUi4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b=QvZReln7; arc=none smtp.client-ip=209.85.167.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b="QvZReln7" Received: by mail-oi1-f178.google.com with SMTP id 5614622812f47-3d21cb38362so196964b6e.2 for ; Wed, 12 Jun 2024 09:54:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1718211271; x=1718816071; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=auZ0CYhLHHpQv2x9Ok7hNHgDuK+aHHonoO28jfXMPus=; b=QvZReln7r68NLkOTDgHWwJzHAQIaTsk73QqqpzeSsyWy9AnHX+yyVgR8Xyqsi1ONlq ZOpBOXgInNueyYB0WcyfSiemEW4DOwt7zufFeo5hGm8/zK5dMobj2NA7dvxc+TQw5kDZ WLLlSYNBg2CjYVjgTma+bHZMCcPGleDq2Js8a5IhB6GPTWiIg5xffaSiF4w6QsWtaxvg IklMz9JCxAXj5+bz1z1hZaEOPQyr9YbcY+s5UYn5HcXZjyo0jwywp/F8x3cyPjw7hsWh HJAVakPnbicQKlt1F0nyXLohZWLy5BZ9TzGsdTeuicjDAkJGZ5kF65kllaFO3g2Yf0R4 PC+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718211271; x=1718816071; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=auZ0CYhLHHpQv2x9Ok7hNHgDuK+aHHonoO28jfXMPus=; b=S7CBdVCNssCqG12icIRCGUBEYn+dZv1sjY96H4+l4dQRG7nfAvkG5ED9sDQwjprneD z0cR8Xz+H92oZSeeV6htV3E4bgO/IWJEEzA7Ey1uJF7qnsqNl2ir1X9RTyFSDhpWp2QE TECY/I5ZfMk0bv8cpH4LzGO3YCRYcFUzh5Kvuci8iJaSGUnW/YWdP1rP9LObmSruUC6q lKubbWhQRCMHuJmEuFwbG4nk/UL/H7BJvO8jBsEmAJWRtPxwA5JzrvQnKZAfFFGJOr7r C32wNxNu2dXXI6WF/XcG39Oz06pawt3peBPWYTsNFTH9fhq2FduIzxCyqZw3kAjzin3K ezWQ== X-Forwarded-Encrypted: i=1; AJvYcCVo5ApFzCjgh6hlzrp+Y2HXYanNqWX5wOXjipT4NivpYh12YOe3Xz8Kadxl6Kg0Luj+qCuYnD50e7OJlbI=@vger.kernel.org X-Gm-Message-State: AOJu0YzHaYISUy8WivtlD6hI99lqDP5GBv48q7lxlc0YkX0xd8aAo/MZ dk4FLTvBWbOGFZgghgSotPkOQuXl0RT0Gos3QWAFHR3cSQS0VNtc/IKIiEY35IQ= X-Google-Smtp-Source: AGHT+IFJcbrN0mfMMLSdZ99zjcbKdGCqyR/7L8hjEBh1nwrgjfG7Nv1hKm/yTAjp6qCBcgUqV8S5Zg== X-Received: by 2002:a05:6808:1520:b0:3d2:1b8a:be6f with SMTP id 5614622812f47-3d23e1841d5mr2768358b6e.4.1718211271170; Wed, 12 Jun 2024 09:54:31 -0700 (PDT) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 5614622812f47-3d2219a6274sm1434752b6e.37.2024.06.12.09.54.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Jun 2024 09:54:30 -0700 (PDT) Message-ID: <795edef9-2bd7-413f-bba2-04d569da63b6@kernel.dk> Date: Wed, 12 Jun 2024 10:54:29 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] aoe: consolidate flags update to prevent race condition To: Gui-Dong Han , justin@coraid.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com References: Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/10/24 9:52 PM, Gui-Dong Han wrote: > In aoecmd_sleepwork, there is a race condition caused by two consecutive > writes to the 'flags' variable within a critical section. If a read > operation occurs between these writes, an intermediate state may be > read, potentially causing bugs. > > To address this issue, the 'flags' variable should be updated in a > single operation to ensure atomicity and prevent any intermediate state > from being read. > > Fixes: 3ae1c24e395b ("[PATCH] aoe [2/8]: support dynamic resizing of AoE devices") > Signed-off-by: Gui-Dong Han > --- > drivers/block/aoe/aoecmd.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c > index cc9077b588d7..37d556f019c0 100644 > --- a/drivers/block/aoe/aoecmd.c > +++ b/drivers/block/aoe/aoecmd.c > @@ -897,8 +897,7 @@ aoecmd_sleepwork(struct work_struct *work) > set_capacity_and_notify(d->gd, d->ssize); > > spin_lock_irq(&d->lock); > - d->flags |= DEVFL_UP; > - d->flags &= ~DEVFL_NEWSIZE; > + d->flags = (d->flags | DEVFL_UP) & ~DEVFL_NEWSIZE; > spin_unlock_irq(&d->lock); > } It's modified under the lock, and any reader should do so as well. If not, there's a race regardless of your change or not. -- Jens Axboe