From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) (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 22E7E30AD05; Wed, 25 Mar 2026 09:54:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774432480; cv=none; b=V2AzGAAgd5qFEmBg3NQGLbJw59vO3CBPJRzWdqPO+oHJB3/caRxpwzeJL/bPHiW+BXXH/fLAKmtb5aPk8Vr8lhMu23TybLs7IzQJgY+tZlZoBzuU6L1RCuXEJB/6v/Cv5XowrH5rZELFaqqymp8GoN0GBMFXvCsbcZVjxWoH8Wo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774432480; c=relaxed/simple; bh=7EiaRxmsVIzYa72CFW/2suQxXAhsJxx/5bUpYhqx88w=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jkDoKJ3YQViLvnkfYBV9l6xuPLiGgNzHdFVizXDL7iYkOJTGNXVEdRBzAttJ6HjMjJv/xBBzqTFSZxHVi70kWclCM20wQV/Hy51sT4e8JfAFlCg12FZlC9UR5+7XwRn/X+ml+DHzB98BHXqdEKAuBCuoallLqOhmfInwEEt9z04= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Ebcqzko2; arc=none smtp.client-ip=198.175.65.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Ebcqzko2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1774432479; x=1805968479; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=7EiaRxmsVIzYa72CFW/2suQxXAhsJxx/5bUpYhqx88w=; b=Ebcqzko2yl/LzAktYB9/u7XG6UasohYvCx9M6qupQQdA60HneiDChE5d GpHH2ZmbV1r5s+zdr2nMDdVs253sPsA9G6SuYxjhlH4faVhzNPCWoJGWd mno6KTxvx3VT+WfwmZJL8FuUtwg4FZkTHGeNPCutUF+SKN9j+9XrgkG8/ 3KGN5JmqtdFE6vBKnVFFfeLJ1W/wzJxe+MPrFW6hBS4aU9grEsaAJFT2c H/pykYP4+NuYxmETewjRK1vL+pedvLifHmpoqLRPx35KYYmeMNhcvOuL/ /gcSljccZmcKLJCIXtkIZSyM9eA/MEsETXJkus2ksVN6xmjtm5nW3X+qc A==; X-CSE-ConnectionGUID: t8UsG0yrRFGJdX3Cj24TfQ== X-CSE-MsgGUID: feZy6lo+TOir7+Y9Uui84A== X-IronPort-AV: E=McAfee;i="6800,10657,11739"; a="98085772" X-IronPort-AV: E=Sophos;i="6.23,139,1770624000"; d="scan'208";a="98085772" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2026 02:54:39 -0700 X-CSE-ConnectionGUID: /IZhftTwRFeN8RRbIFHKAQ== X-CSE-MsgGUID: 5hkeYRO+TG2NXMhTecI1FQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,139,1770624000"; d="scan'208";a="226267337" Received: from dalessan-mobl3.ger.corp.intel.com (HELO localhost) ([10.245.245.32]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2026 02:54:37 -0700 Date: Wed, 25 Mar 2026 11:54:34 +0200 From: Andy Shevchenko To: Felix Gu Cc: Mark Brown , linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 1/1] spi: Simplify devm_spi_*_controller() Message-ID: References: <176797260995.67850.318976521283878747.b4-ty@kernel.org> <20260324145548.139952-1-ustc.gu@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260324145548.139952-1-ustc.gu@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo On Tue, Mar 24, 2026 at 10:55:48PM +0800, Felix Gu wrote: ... > > int devm_spi_register_controller(struct device *dev, > > struct spi_controller *ctlr) > > { > > - struct spi_controller **ptr; > > int ret; > > > > - ptr = devres_alloc(devm_spi_unregister, sizeof(*ptr), GFP_KERNEL); > > - if (!ptr) > > - return -ENOMEM; > > - > > ret = spi_register_controller(ctlr); > > - if (!ret) { > > - *ptr = ctlr; > > - devres_add(dev, ptr); > > - } else { > > - devres_free(ptr); > > - } > > + if (ret) > > + return ret; > > + > > + return devm_add_action_or_reset(dev, devm_spi_unregister_controller, ctlr); > > > > - return ret; > > } > It seems has a potential corner case in this commit. > > The issue is that devm_add_action_or_reset() triggers its callback > immediately if the internal devres allocation fails. Yes, it does. > This creates the following sequence: > 1. spi_register_controller(ctlr) succeeds. > 2. devm_add_action_or_reset() is called but fails. > 3. The "reset" triggers devm_spi_unregister_controller(ctlr) immediately. > 4. This calls spi_unregister_controller(ctlr). > 5. For controllers allocated via spi_alloc_host() (where > ctlr->devm_allocated is false), spi_unregister_controller() calls > put_device(&ctlr->dev). > 6. This drops the reference count to zero and frees the ctlr structure. I am not sure I see how the sequence is different from the say this ret = spi_register_controller(...) if (ret) goto err; // ...if success do something else... ret = foo(); if (ret) { spi_unregister_controller(...); goto err; } So, each driver should be prepared for an error handling in which it should release resources in the reversed order. > However, the driver still holds the ctlr pointer and will typically > attempt its own cleanup, leading to a use-after-free or double-free. You mean buggy driver? Any real example of the use case? In the 5. you implied something like ret = spi_alloc_host(); ... ret = devm_spi_register_controller() ? But this is against the rule how devm must be used. > What are your thoughts on this? Does this analysis seem correct, or am > I missing a detail in how the refcounting is handled here? Is this analysis AI assisted? -- With Best Regards, Andy Shevchenko