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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9EAC8C11F66 for ; Wed, 14 Jul 2021 08:35:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D641613AB for ; Wed, 14 Jul 2021 08:35:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238545AbhGNIiI (ORCPT ); Wed, 14 Jul 2021 04:38:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238503AbhGNIiH (ORCPT ); Wed, 14 Jul 2021 04:38:07 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54A5EC06175F for ; Wed, 14 Jul 2021 01:35:16 -0700 (PDT) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id B0871CC; Wed, 14 Jul 2021 10:35:14 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1626251714; bh=Twf37gpHkRFjIZj4IaTADsPtFGmGBJ8mFS3zLfz31Og=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lEupGLOMyaIutQvPv2pGN3xj08n77MWY4dL4fUFY3/SfUUAMnY56K1aqB4nfJHjf5 zklaNCszTZ5hpvQOdSyWmHLbYsutRTAVjIBzCDSWn0n4AIbp19vlYeLXJKiarSubvA GXTQ5jDIVqDpQDkkQhC3MN+xswFRnfIGVu/HuHF0= Date: Wed, 14 Jul 2021 11:35:13 +0300 From: Laurent Pinchart To: Steven Price Cc: Daniel Vetter , David Airlie , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Biju Das Subject: Re: [PATCH] drm/of: free the iterator object on failure Message-ID: References: <20210712155758.48286-1-steven.price@arm.com> <5c3db755-c3fb-dfe7-3d23-bbbcc81af3d8@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5c3db755-c3fb-dfe7-3d23-bbbcc81af3d8@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steven, On Tue, Jul 13, 2021 at 05:16:16PM +0100, Steven Price wrote: > On 12/07/2021 22:55, Laurent Pinchart wrote: > > On Mon, Jul 12, 2021 at 10:31:52PM +0100, Steven Price wrote: > >> On 12/07/2021 17:50, Laurent Pinchart wrote: > >>> On Mon, Jul 12, 2021 at 04:57:58PM +0100, Steven Price wrote: > >>>> When bailing out due to the sanity check the iterator value needs to be > >>>> freed because the early return prevents for_each_child_of_node() from > >>>> doing the dereference itself. > >>>> > >>>> Fixes: 4ee48cc5586b ("drm: of: Fix double-free bug") > >>> > >>> I don't think the Fixes tag is correct, the issue was already present > >>> before 4ee48cc5586b. The fix looks right though. > >> > >> I'm not sure quite what you mean by "already present". As I understand > >> it the timeline was: > >> > >> 1. 6529007522de drm: of: Add drm_of_lvds_get_dual_link_pixel_order > >> The function was originally added. This made the mistake twice of > >> calling of_node_put() on the wrong variable (remote_port rather than > >> endpoint). > > > > Correct. > > > >> 2. 4ee48cc5586b drm: of: Fix double-free bug > >> One of the of_node_put() calls was removed as it was a double-free. > >> This left the first incorrect of_node_put() in place, and the second > >> is now a straight leak. > > > > That's right, but this commit didn't introduce the leak, it was already > > there in 6529007522de (in addition to the double-free). > > Ah, I see what you mean. My thought process was that the original > comment had the bug "using the wrong variable", and (2) (partially) > fixed that but in the process introduced a new bug (a memory leak). But > I guess technically the memory leak was there from the beginning. > > The other reason I referenced (2) in the Fixes line is because this > patch depends on patch (2), whereas it won't apply cleanly without. > > However I don't think it really matters either way: (2) has already been > backported, and either way this needs fixing if either (1) or (2) are > present. > > Would you like me to resend with a "Fixes: 6529007522de drm: of: Add > drm_of_lvds_get_dual_link_pixel_order", or are you happy to just fix > this up when merging? I don't mind either way, from my point of view it can be fixed up by whoever will pick the patch up and merge it. > >> 3. b557a5f8da57 drm/of: free the right object > >> This (correctly) fixes the first of_node_put() to free endpoint. And > >> the post from Daniel was what caused me to look. > >> > >> 4. This patch > >> Reintroduces the of_node_put() removed in (2) but putting endpoint > >> rather than remote_port. > >> > >> I've put (2) in the Fixes line as this patch is fixing the leak > >> introduced by that patch, but that in itself was of course 'fixing' the > >> double free of the original patch. > >> > >>>> Signed-off-by: Steven Price > >>>> --- > >>>> drivers/gpu/drm/drm_of.c | 4 +++- > >>>> 1 file changed, 3 insertions(+), 1 deletion(-) > >>>> > >>>> Daniel's email[1] made me take a look at this function and it appears > >>>> that for_each_child_of_node()'s interface had caused a bad bug fix due > >>>> to the hidden reference counting in the iterator. > >>>> > >>>> [1] https://lore.kernel.org/r/YOxQ5TbkNrqCGBDJ%40phenom.ffwll.local > >>>> > >>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c > >>>> index 197c57477344..997b8827fed2 100644 > >>>> --- a/drivers/gpu/drm/drm_of.c > >>>> +++ b/drivers/gpu/drm/drm_of.c > >>>> @@ -331,8 +331,10 @@ static int drm_of_lvds_get_remote_pixels_type( > >>>> * configurations by passing the endpoints explicitly to > >>>> * drm_of_lvds_get_dual_link_pixel_order(). > >>>> */ > >>>> - if (!current_pt || pixels_type != current_pt) > >>>> + if (!current_pt || pixels_type != current_pt) { > >>>> + of_node_put(endpoint); > >>>> return -EINVAL; > >>>> + } > >>>> } > >>>> > >>>> return pixels_type; -- Regards, Laurent Pinchart 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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B52B8C07E9A for ; Wed, 14 Jul 2021 08:35:17 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 792736136E for ; Wed, 14 Jul 2021 08:35:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 792736136E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E84626E1B6; Wed, 14 Jul 2021 08:35:16 +0000 (UTC) Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id 407AB6E1B6 for ; Wed, 14 Jul 2021 08:35:16 +0000 (UTC) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id B0871CC; Wed, 14 Jul 2021 10:35:14 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1626251714; bh=Twf37gpHkRFjIZj4IaTADsPtFGmGBJ8mFS3zLfz31Og=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lEupGLOMyaIutQvPv2pGN3xj08n77MWY4dL4fUFY3/SfUUAMnY56K1aqB4nfJHjf5 zklaNCszTZ5hpvQOdSyWmHLbYsutRTAVjIBzCDSWn0n4AIbp19vlYeLXJKiarSubvA GXTQ5jDIVqDpQDkkQhC3MN+xswFRnfIGVu/HuHF0= Date: Wed, 14 Jul 2021 11:35:13 +0300 From: Laurent Pinchart To: Steven Price Subject: Re: [PATCH] drm/of: free the iterator object on failure Message-ID: References: <20210712155758.48286-1-steven.price@arm.com> <5c3db755-c3fb-dfe7-3d23-bbbcc81af3d8@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5c3db755-c3fb-dfe7-3d23-bbbcc81af3d8@arm.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Thomas Zimmermann , Biju Das Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Steven, On Tue, Jul 13, 2021 at 05:16:16PM +0100, Steven Price wrote: > On 12/07/2021 22:55, Laurent Pinchart wrote: > > On Mon, Jul 12, 2021 at 10:31:52PM +0100, Steven Price wrote: > >> On 12/07/2021 17:50, Laurent Pinchart wrote: > >>> On Mon, Jul 12, 2021 at 04:57:58PM +0100, Steven Price wrote: > >>>> When bailing out due to the sanity check the iterator value needs to be > >>>> freed because the early return prevents for_each_child_of_node() from > >>>> doing the dereference itself. > >>>> > >>>> Fixes: 4ee48cc5586b ("drm: of: Fix double-free bug") > >>> > >>> I don't think the Fixes tag is correct, the issue was already present > >>> before 4ee48cc5586b. The fix looks right though. > >> > >> I'm not sure quite what you mean by "already present". As I understand > >> it the timeline was: > >> > >> 1. 6529007522de drm: of: Add drm_of_lvds_get_dual_link_pixel_order > >> The function was originally added. This made the mistake twice of > >> calling of_node_put() on the wrong variable (remote_port rather than > >> endpoint). > > > > Correct. > > > >> 2. 4ee48cc5586b drm: of: Fix double-free bug > >> One of the of_node_put() calls was removed as it was a double-free. > >> This left the first incorrect of_node_put() in place, and the second > >> is now a straight leak. > > > > That's right, but this commit didn't introduce the leak, it was already > > there in 6529007522de (in addition to the double-free). > > Ah, I see what you mean. My thought process was that the original > comment had the bug "using the wrong variable", and (2) (partially) > fixed that but in the process introduced a new bug (a memory leak). But > I guess technically the memory leak was there from the beginning. > > The other reason I referenced (2) in the Fixes line is because this > patch depends on patch (2), whereas it won't apply cleanly without. > > However I don't think it really matters either way: (2) has already been > backported, and either way this needs fixing if either (1) or (2) are > present. > > Would you like me to resend with a "Fixes: 6529007522de drm: of: Add > drm_of_lvds_get_dual_link_pixel_order", or are you happy to just fix > this up when merging? I don't mind either way, from my point of view it can be fixed up by whoever will pick the patch up and merge it. > >> 3. b557a5f8da57 drm/of: free the right object > >> This (correctly) fixes the first of_node_put() to free endpoint. And > >> the post from Daniel was what caused me to look. > >> > >> 4. This patch > >> Reintroduces the of_node_put() removed in (2) but putting endpoint > >> rather than remote_port. > >> > >> I've put (2) in the Fixes line as this patch is fixing the leak > >> introduced by that patch, but that in itself was of course 'fixing' the > >> double free of the original patch. > >> > >>>> Signed-off-by: Steven Price > >>>> --- > >>>> drivers/gpu/drm/drm_of.c | 4 +++- > >>>> 1 file changed, 3 insertions(+), 1 deletion(-) > >>>> > >>>> Daniel's email[1] made me take a look at this function and it appears > >>>> that for_each_child_of_node()'s interface had caused a bad bug fix due > >>>> to the hidden reference counting in the iterator. > >>>> > >>>> [1] https://lore.kernel.org/r/YOxQ5TbkNrqCGBDJ%40phenom.ffwll.local > >>>> > >>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c > >>>> index 197c57477344..997b8827fed2 100644 > >>>> --- a/drivers/gpu/drm/drm_of.c > >>>> +++ b/drivers/gpu/drm/drm_of.c > >>>> @@ -331,8 +331,10 @@ static int drm_of_lvds_get_remote_pixels_type( > >>>> * configurations by passing the endpoints explicitly to > >>>> * drm_of_lvds_get_dual_link_pixel_order(). > >>>> */ > >>>> - if (!current_pt || pixels_type != current_pt) > >>>> + if (!current_pt || pixels_type != current_pt) { > >>>> + of_node_put(endpoint); > >>>> return -EINVAL; > >>>> + } > >>>> } > >>>> > >>>> return pixels_type; -- Regards, Laurent Pinchart