From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EEB5C4708D for ; Wed, 7 Dec 2022 21:56:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229521AbiLGV4M (ORCPT ); Wed, 7 Dec 2022 16:56:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229543AbiLGV4L (ORCPT ); Wed, 7 Dec 2022 16:56:11 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EBA5063D5B; Wed, 7 Dec 2022 13:56:10 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 86B4161BA9; Wed, 7 Dec 2022 21:56:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9B46C433C1; Wed, 7 Dec 2022 21:56:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1670450169; bh=gEYTNmacgKJxqisPli8O3MFeQnqOQgkhZN0A5c7VPWc=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=eGhUiK/9t1orhE9FKIhT+41yvZiOYWhnOBaN9JfQI43Ai0JJOZiDCRe4y9s+Lhq7Z zl0oLhqqS6D/cJnQCYunHG4K4AC/2vX3gtf+fueoN5AxztNEXF/3m5GCse1/SQOmgm YjVC/vNjuqVe9cxCRc/Ww/I8iZu7HKfxi65pouwWBYZSD8Rt5gc6nflzENEBdtJoRp JbvesL/zFDR8aWfx409blR+hvVO9gtg5HVuuFS+U2onQFuvcqjHrcELlva9PxeE0gV r8BkEYXlNy9lmlWz7iK5EpNPntY1XQjJdWhxrJl9uq+oga+HlJ2lYPRqOU0cv8zhF8 zzKZK57py9tjg== Date: Wed, 7 Dec 2022 15:56:08 -0600 From: Bjorn Helgaas To: Stephen Kitt Cc: linux-kernel@vger.kernel.org, Bjorn Helgaas , linux-pci@vger.kernel.org, Jan Rueth Subject: Re: [PATCH] PCI/ASPM: Call pcie_aspm_sanity_check() as late as possible Message-ID: <20221207215608.GA1471870@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221006115950.821736-1-steve@sk2.org> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org [+cc Jan] On Thu, Oct 06, 2022 at 01:59:50PM +0200, Stephen Kitt wrote: > In pcie_aspm_init_link_state(), a number of checks are made to > determine whether the function should proceed, before the result of > the call to pcie_aspm_sanity_check() is actually used. The latter > function doesn't change any state, it only reports a result, so > calling it later doesn't make any difference to the state of the > devices or the information we have about them. But having the call > early reportedly can cause null-pointer dereferences; see > https://unix.stackexchange.com/q/322337 for one example with > pcie_aspm=off (this was reported in 2016, but the relevant code hasn't > changed since then). Thanks, Stephen! That stackexchange report doesn't have much information, but it looks similar to this old report from Jan Rueth, which I'm sorry to say I never got resolved: https://bugzilla.kernel.org/show_bug.cgi?id=187731 https://lore.kernel.org/all/4cec62c2-218a-672b-8c12-d44e8df56aae@comsys.rwth-aachen.de/#t And Jan's patch is almost identical to yours :) I hope to get this resolved, but I don't have time to work on it before the upcoming merge window, which will probably open Sunday. And then it's holiday time, so it may be January before I get back to it. I'm just dropping the links here as breadcrumbs for picking this back up. Bjorn > This moves the call to pcie_aspm_sanity_check() just before the result > is actually used, giving all the other checks a chance to run first. > > Signed-off-by: Stephen Kitt > --- > drivers/pci/pcie/aspm.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index a8aec190986c..38df439568b7 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -889,7 +889,7 @@ static void pcie_aspm_update_sysfs_visibility(struct pci_dev *pdev) > void pcie_aspm_init_link_state(struct pci_dev *pdev) > { > struct pcie_link_state *link; > - int blacklist = !!pcie_aspm_sanity_check(pdev); > + int blacklist; > > if (!aspm_support_enabled) > return; > @@ -923,6 +923,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev) > * upstream links also because capable state of them can be > * update through pcie_aspm_cap_init(). > */ > + blacklist = !!pcie_aspm_sanity_check(pdev); > pcie_aspm_cap_init(link, blacklist); > > /* Setup initial Clock PM state */ > > base-commit: 833477fce7a14d43ae4c07f8ddc32fa5119471a2 > -- > 2.30.2 >