From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CA25F19D092; Mon, 2 Feb 2026 01:21:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769995305; cv=none; b=i32xnYWddGfXEQKDcPNSEyhZM2kHpU0aGo/qYqhL+InzZFnlnM0hj+C0V41LusmBY+c2ScybRfI7/tch/nOm+v7fGyhAqJzru0x/lq6vyQNFyfp2BMMy8fzurQ+7GeWn7FAtJBFdbsWiJU0BgIsInE06SPzWmD0x5mzl400h7o0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769995305; c=relaxed/simple; bh=mCK4jAurctXneO9NLzv7RMZBD5H3BIpLk3Fp60fsWxU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aZ8JkZbVTvDe0DO2rUakiAWDU2+0A0T10u//dWnmCoFtFjYZQZxowkbOpXuXlJ4PiZGpbs47jJWpvWqtWbIQYJL+ROvgwikX59zqNcVXV/9zCkzHUKbekEj3EImsZrski7NcPi5nHoQUYSu4AgfVlXnA0wDrg5nM6awwHoei6PE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=klpxed5X; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="klpxed5X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02974C4CEF7; Mon, 2 Feb 2026 01:21:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769995305; bh=mCK4jAurctXneO9NLzv7RMZBD5H3BIpLk3Fp60fsWxU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=klpxed5Xdavgeds3eRzynfyHMTTTXl5f1xLv1v8zb9GyelRdFc08i/w9pCcdIjx2z 7catgkmMruYIG/r891AILjUrqgNDpRQzC65jF1eKMKeBP/LxrMzjI53yYc0i3SwQ3/ YK6OwpL9k54Aew/q1gmw0pH0BCxWOeGiu3UrE7bFpe5jkieVOT/VxsF0t9jvvnVGGF ECrcix4VvT2lX/Ou3F9AHoROCAepiFYXI+6tM4iAokFwf8fcO8IlJj1Ri6bzgFY7Cg N80FqHo4A94W2DwmOGIkoraFVD4YnoM4QsxQ8q81VsN/7GcjAe0hfx05apbtNlsorQ mLVn+HWFzASgA== Message-ID: Date: Mon, 2 Feb 2026 10:21:43 +0900 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] scsi: libsas: Fix dev_list race conditions with proper locking To: Chaohai Chen Cc: john.g.garry@oracle.com, yanaijie@huawei.com, James.Bottomley@hansenpartnership.com, martin.petersen@oracle.com, johannes.thumshirn@wdc.com, mingo@kernel.org, cassel@kernel.org, tglx@kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260129093859.1418749-1-wdhh6@aliyun.com> Content-Language: en-US From: Damien Le Moal Organization: Western Digital Research In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/31/26 20:19, Chaohai Chen wrote: >>> + * We need to unlock before calling sas_unregister_dev() as it >>> + * may sleep, but we hold a reference to prevent device removal. >> >> And why is that necessary ? >> > Because when unlocked, it is possible that the device has already been > released by another thread. If there is no reference count, it will lead > to used after free. Please clearly explain the problem path. Your statements about "another thread" is too vague. >>> + */ >>> + spin_lock_irq(&port->dev_list_lock); >>> list_for_each_entry_safe_reverse(dev, n, &port->dev_list, dev_list_node) { >>> if (gone) >>> set_bit(SAS_DEV_GONE, &dev->state); >>> + kref_get(&dev->kref); >>> + spin_unlock_irq(&port->dev_list_lock); >>> + >>> sas_unregister_dev(port, dev); >>> + sas_put_device(dev); >>> + >>> + spin_lock_irq(&port->dev_list_lock); >>> } >>> + spin_unlock_irq(&port->dev_list_lock); -- Damien Le Moal Western Digital Research