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 70113C433F5 for ; Fri, 8 Apr 2022 23:44:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239450AbiDHXqT (ORCPT ); Fri, 8 Apr 2022 19:46:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230302AbiDHXqM (ORCPT ); Fri, 8 Apr 2022 19:46:12 -0400 Received: from mail-wr1-x432.google.com (mail-wr1-x432.google.com [IPv6:2a00:1450:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77FCA3284D2; Fri, 8 Apr 2022 16:44:06 -0700 (PDT) Received: by mail-wr1-x432.google.com with SMTP id w21so15052935wra.2; Fri, 08 Apr 2022 16:44:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=YNQXgXF4a+AhQ5fk56t1rPp4GV4Eh6u4vBLfJhuC6Ys=; b=iTRU9sdAsgx9eWRliBtBRr63Z5e8AyHmLzBsYaphNbucwkdJkhfTsbMRa10o5/uTRx 527BqGDl0qWnAxrsDFvYx9R+NwBNbAdCm6Gh2zqgsAg9DKyhgtLk5EA8cnCNx89SEAC9 +PGfvdr2LXPyRCmnrsYQkfVfiO+Zt8C/pcz7M+B4dvoMkE69NOk7v9fefgXFiz6f+r6k 45imaU5PyMhOMdTKceEw92MUgh4fc5iXRSjJrRqM8WhTlk9wDqOfM7GpsNH4UlHVDfbz 0uKzuviz+FElrM1Y4jAH91tRyrn0D8h6amZ0zNswRi9dzea0dvbtzZDjJKp5JILL7AbV 2RBg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=YNQXgXF4a+AhQ5fk56t1rPp4GV4Eh6u4vBLfJhuC6Ys=; b=hvQAB9aHRP3AcVzIIN0NgyoKpF0cjawlLzRl2PbIKJOhWvhppoXNSAGrRC8Je2Q7MB Kki8rXC5gP0zMqySA1cAioRZ1+wQ3u/EYWQheRJSGEZk8G4hlxi5DJyZUehCKb5j+a/L D9Egft7aBAteA8fe1ppk0kYfvDGrCl8dVknYbYzyzS9+Q3gCQB/UkwzWZJ5yeJBKDQSc RUAgWXPyszpDn23WOtp/p+WxUE1bNYk4mSo/G3mPMLdaCvmaACSY9EFufcQFQpdMFMQ1 OZovJjJIFmlfazMgRTlJ1HipgOHsGO8LBemaBVNG0pKE/iofS4Va8QwUOgWI1FHHDA84 TiqA== X-Gm-Message-State: AOAM530ia4gk/nlRW90q3fG3LpwSYFmpYPyx/ubdUVPdwkDEKOU0tMDO Uu3U3oSgUxWzY4jT3z2P1tSHxNSzCFpNVQ== X-Google-Smtp-Source: ABdhPJzzLLnXf2ONfrh6vC07vhyIaQnj82N/7MyyvAuh0zOKcQSQs1IEMtYxncGiJqhX7MnvnzAqiw== X-Received: by 2002:a05:6000:18a3:b0:204:1f84:287e with SMTP id b3-20020a05600018a300b002041f84287emr16771491wri.184.1649461444869; Fri, 08 Apr 2022 16:44:04 -0700 (PDT) Received: from smtpclient.apple ([185.238.38.242]) by smtp.gmail.com with ESMTPSA id p19-20020a05600c359300b0038c7d1086a7sm12496919wmq.1.2022.04.08.16.44.03 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Apr 2022 16:44:04 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.80.82.1.1\)) Subject: Re: [PATCH net-next 03/15] net: dsa: mv88e6xxx: Replace usage of found with dedicated iterator From: Jakob Koschel In-Reply-To: <20220408123101.p33jpynhqo67hebe@skbuf> Date: Sat, 9 Apr 2022 01:44:00 +0200 Cc: "David S. Miller" , Jakub Kicinski , Paolo Abeni , Andrew Lunn , Vivien Didelot , Florian Fainelli , Lars Povlsen , Steen Hegelund , UNGLinuxDriver@microchip.com, Ariel Elior , Manish Chopra , Edward Cree , Martin Habets , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Jiri Pirko , Casper Andersson , Bjarni Jonasson , Colin Ian King , Michael Walle , Christophe JAILLET , Arnd Bergmann , Eric Dumazet , Di Zhu , Xu Wang , Netdev , LKML , Linux ARM , linuxppc-dev , Mike Rapoport , Brian Johannesmeyer , Cristiano Giuffrida , "Bos, H.J." Content-Transfer-Encoding: quoted-printable Message-Id: References: <20220407102900.3086255-1-jakobkoschel@gmail.com> <20220407102900.3086255-4-jakobkoschel@gmail.com> <20220408123101.p33jpynhqo67hebe@skbuf> To: Vladimir Oltean X-Mailer: Apple Mail (2.3696.80.82.1.1) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vladimir, > On 8. Apr 2022, at 14:31, Vladimir Oltean wrote: >=20 > Hi Jakob, >=20 > On Thu, Apr 07, 2022 at 12:28:48PM +0200, Jakob Koschel wrote: >> To move the list iterator variable into the list_for_each_entry_*() >> macro in the future it should be avoided to use the list iterator >> variable after the loop body. >>=20 >> To *never* use the list iterator variable after the loop it was >> concluded to use a separate iterator variable instead of a >> found boolean [1]. >>=20 >> This removes the need to use a found variable and simply checking if >> the variable was set, can determine if the break/goto was hit. >>=20 >> Link: = https://lore.kernel.org/all/CAHk-=3DwgRr_D8CB-D9Kg-c=3DEHreAsk5SqXPwr9Y7k9= sA6cWXJ6w@mail.gmail.com/ [1] >> Signed-off-by: Jakob Koschel >> --- >> drivers/net/dsa/mv88e6xxx/chip.c | 21 ++++++++++----------- >> 1 file changed, 10 insertions(+), 11 deletions(-) >>=20 >> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c = b/drivers/net/dsa/mv88e6xxx/chip.c >> index 64f4fdd02902..f254f537c357 100644 >> --- a/drivers/net/dsa/mv88e6xxx/chip.c >> +++ b/drivers/net/dsa/mv88e6xxx/chip.c >> @@ -1381,28 +1381,27 @@ static int mv88e6xxx_set_mac_eee(struct = dsa_switch *ds, int port, >> /* Mask of the local ports allowed to receive frames from a given = fabric port */ >> static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, = int port) >> { >> + struct dsa_port *dp =3D NULL, *iter, *other_dp; >> struct dsa_switch *ds =3D chip->ds; >> struct dsa_switch_tree *dst =3D ds->dst; >> - struct dsa_port *dp, *other_dp; >> - bool found =3D false; >> u16 pvlan; >>=20 >> /* dev is a physical switch */ >> if (dev <=3D dst->last_switch) { >> - list_for_each_entry(dp, &dst->ports, list) { >> - if (dp->ds->index =3D=3D dev && dp->index =3D=3D = port) { >> - /* dp might be a DSA link or a user = port, so it >> + list_for_each_entry(iter, &dst->ports, list) { >> + if (iter->ds->index =3D=3D dev && iter->index =3D=3D= port) { >> + /* iter might be a DSA link or a user = port, so it >> * might or might not have a bridge. >> - * Use the "found" variable for both = cases. >> + * Set the "dp" variable for both cases. >> */ >> - found =3D true; >> + dp =3D iter; >> break; >> } >> } >> /* dev is a virtual bridge */ >> } else { >> - list_for_each_entry(dp, &dst->ports, list) { >> - unsigned int bridge_num =3D = dsa_port_bridge_num_get(dp); >> + list_for_each_entry(iter, &dst->ports, list) { >> + unsigned int bridge_num =3D = dsa_port_bridge_num_get(iter); >>=20 >> if (!bridge_num) >> continue; >> @@ -1410,13 +1409,13 @@ static u16 mv88e6xxx_port_vlan(struct = mv88e6xxx_chip *chip, int dev, int port) >> if (bridge_num + dst->last_switch !=3D dev) >> continue; >>=20 >> - found =3D true; >> + dp =3D iter; >> break; >> } >> } >>=20 >> /* Prevent frames from unknown switch or virtual bridge */ >> - if (!found) >> + if (!dp) >> return 0; >>=20 >> /* Frames from DSA links and CPU ports can egress any local port = */ >> --=20 >> 2.25.1 >>=20 >=20 > Let's try to not make convoluted code worse. Do the following 2 = patches > achieve what you are looking for? Originally I had a single patch = (what > is now 2/2) but I figured it would be cleaner to break out the = unrelated > change into what is now 1/2. I do agree with not making convoluted code worse, but I was reluctant = with e.g. introducing new functions for this because others essentially have the opposite opinion on this. I however like solving it that way, it makes it a lot cleaner. >=20 > If you want I can submit these changes separately. Sure if you want to submit them separately, go ahead. Otherwise I can integrate it into a v2, whatever you prefer essentially. >=20 > -----------------------------[ cut here ]----------------------------- > =46rom 2d84ecd87566b1535a04526b4ebb2764e764625f Mon Sep 17 00:00:00 = 2001 > From: Vladimir Oltean > Date: Fri, 8 Apr 2022 15:15:30 +0300 > Subject: [PATCH 1/2] net: dsa: mv88e6xxx: remove redundant check in > mv88e6xxx_port_vlan() >=20 > We know that "dev > dst->last_switch" in the "else" block. > In other words, that "dev - dst->last_switch" is > 0. >=20 > dsa_port_bridge_num_get(dp) can be 0, but the check > "if (bridge_num + dst->last_switch !=3D dev) continue", rewritten as > "if (bridge_num !=3D dev - dst->last_switch) continue", aka > "if (bridge_num !=3D something which cannot be 0) continue", > makes it redundant to have the extra "if (!bridge_num) continue" = logic, > since a bridge_num of zero would have been skipped anyway. >=20 > Signed-off-by: Vladimir Oltean > --- > drivers/net/dsa/mv88e6xxx/chip.c | 3 --- > 1 file changed, 3 deletions(-) >=20 > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c = b/drivers/net/dsa/mv88e6xxx/chip.c > index 64f4fdd02902..b3aa0e5bc842 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -1404,9 +1404,6 @@ static u16 mv88e6xxx_port_vlan(struct = mv88e6xxx_chip *chip, int dev, int port) > list_for_each_entry(dp, &dst->ports, list) { > unsigned int bridge_num =3D = dsa_port_bridge_num_get(dp); >=20 > - if (!bridge_num) > - continue; > - > if (bridge_num + dst->last_switch !=3D dev) > continue; >=20 > -----------------------------[ cut here ]----------------------------- >=20 > -----------------------------[ cut here ]----------------------------- > =46rom dabafdbe38b408f7c563ad91fc6e57791055fed7 Mon Sep 17 00:00:00 = 2001 > From: Vladimir Oltean > Date: Fri, 8 Apr 2022 14:57:45 +0300 > Subject: [PATCH 2/2] net: dsa: mv88e6xxx: refactor = mv88e6xxx_port_vlan() >=20 > To avoid bugs and speculative execution exploits due to type-confused > pointers at the end of a list_for_each_entry() loop, one measure is to > restrict code to not use the iterator variable outside the loop block. >=20 > In the case of mv88e6xxx_port_vlan(), this isn't a problem, as we = never > let the loops exit through "natural causes" anyway, by using a "found" > variable and then using the last "dp" iterator prior to the break, = which > is a safe thing to do. >=20 > Nonetheless, with the expected new syntax, this pattern will no longer > be possible. >=20 > Profit off of the occasion and break the two port finding methods into > smaller sub-functions. Somehow, returning a copy of the iterator = pointer > is still accepted. >=20 > This change makes it redundant to have a "bool found", since the "dp" > from mv88e6xxx_port_vlan() now holds NULL if we haven't found what we > were looking for. >=20 > Signed-off-by: Vladimir Oltean > --- > drivers/net/dsa/mv88e6xxx/chip.c | 54 ++++++++++++++++++-------------- > 1 file changed, 31 insertions(+), 23 deletions(-) >=20 > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c = b/drivers/net/dsa/mv88e6xxx/chip.c > index b3aa0e5bc842..1f35e89053e6 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -1378,42 +1378,50 @@ static int mv88e6xxx_set_mac_eee(struct = dsa_switch *ds, int port, > return 0; > } >=20 > +static struct dsa_port *mv88e6xxx_find_port(struct dsa_switch_tree = *dst, > + int sw_index, int port) > +{ > + struct dsa_port *dp; > + > + list_for_each_entry(dp, &dst->ports, list) > + if (dp->ds->index =3D=3D sw_index && dp->index =3D=3D = port) > + return dp; > + > + return NULL; > +} > + > +static struct dsa_port * > +mv88e6xxx_find_port_by_bridge_num(struct dsa_switch_tree *dst, > + unsigned int bridge_num) > +{ > + struct dsa_port *dp; > + > + list_for_each_entry(dp, &dst->ports, list) > + if (dsa_port_bridge_num_get(dp) =3D=3D bridge_num) > + return dp; > + > + return NULL; > +} > + > /* Mask of the local ports allowed to receive frames from a given = fabric port */ > static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, = int port) > { > struct dsa_switch *ds =3D chip->ds; > struct dsa_switch_tree *dst =3D ds->dst; > struct dsa_port *dp, *other_dp; > - bool found =3D false; > u16 pvlan; >=20 > - /* dev is a physical switch */ > if (dev <=3D dst->last_switch) { > - list_for_each_entry(dp, &dst->ports, list) { > - if (dp->ds->index =3D=3D dev && dp->index =3D=3D = port) { > - /* dp might be a DSA link or a user = port, so it > - * might or might not have a bridge. > - * Use the "found" variable for both = cases. > - */ > - found =3D true; > - break; > - } > - } > - /* dev is a virtual bridge */ > + /* dev is a physical switch */ > + dp =3D mv88e6xxx_find_port(dst, dev, port); > } else { > - list_for_each_entry(dp, &dst->ports, list) { > - unsigned int bridge_num =3D = dsa_port_bridge_num_get(dp); > - > - if (bridge_num + dst->last_switch !=3D dev) > - continue; > - > - found =3D true; > - break; > - } > + /* dev is a virtual bridge */ > + dp =3D mv88e6xxx_find_port_by_bridge_num(dst, > + dev - = dst->last_switch); > } >=20 > /* Prevent frames from unknown switch or virtual bridge */ > - if (!found) > + if (!dp) > return 0; >=20 > /* Frames from DSA links and CPU ports can egress any local port = */ > -----------------------------[ cut here ]----------------------------- Thanks, Jakob 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 95F70C433F5 for ; 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Fri, 08 Apr 2022 16:44:04 -0700 (PDT) Received: from smtpclient.apple ([185.238.38.242]) by smtp.gmail.com with ESMTPSA id p19-20020a05600c359300b0038c7d1086a7sm12496919wmq.1.2022.04.08.16.44.03 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Apr 2022 16:44:04 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.80.82.1.1\)) Subject: Re: [PATCH net-next 03/15] net: dsa: mv88e6xxx: Replace usage of found with dedicated iterator From: Jakob Koschel In-Reply-To: <20220408123101.p33jpynhqo67hebe@skbuf> Date: Sat, 9 Apr 2022 01:44:00 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: References: <20220407102900.3086255-1-jakobkoschel@gmail.com> <20220407102900.3086255-4-jakobkoschel@gmail.com> <20220408123101.p33jpynhqo67hebe@skbuf> To: Vladimir Oltean X-Mailer: Apple Mail (2.3696.80.82.1.1) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Lunn , Cristiano Giuffrida , Eric Dumazet , Paul Mackerras , Ariel Elior , Florian Fainelli , Manish Chopra , "David S. Miller" , Steen Hegelund , "Bos, H.J." , Linux ARM , Martin Habets , Paolo Abeni , Vivien Didelot , Bjarni Jonasson , Jiri Pirko , Arnd Bergmann , Brian Johannesmeyer , Christophe JAILLET , Jakub Kicinski , Di Zhu , Lars Povlsen , Netdev , LKML , UNGLinuxDriver@microchip.com, Edward Cree , Michael Walle , Xu Wang , Colin Ian King , linuxppc-dev , Casper Andersson , Mike Rapoport Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Vladimir, > On 8. Apr 2022, at 14:31, Vladimir Oltean wrote: >=20 > Hi Jakob, >=20 > On Thu, Apr 07, 2022 at 12:28:48PM +0200, Jakob Koschel wrote: >> To move the list iterator variable into the list_for_each_entry_*() >> macro in the future it should be avoided to use the list iterator >> variable after the loop body. >>=20 >> To *never* use the list iterator variable after the loop it was >> concluded to use a separate iterator variable instead of a >> found boolean [1]. >>=20 >> This removes the need to use a found variable and simply checking if >> the variable was set, can determine if the break/goto was hit. >>=20 >> Link: = https://lore.kernel.org/all/CAHk-=3DwgRr_D8CB-D9Kg-c=3DEHreAsk5SqXPwr9Y7k9= sA6cWXJ6w@mail.gmail.com/ [1] >> Signed-off-by: Jakob Koschel >> --- >> drivers/net/dsa/mv88e6xxx/chip.c | 21 ++++++++++----------- >> 1 file changed, 10 insertions(+), 11 deletions(-) >>=20 >> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c = b/drivers/net/dsa/mv88e6xxx/chip.c >> index 64f4fdd02902..f254f537c357 100644 >> --- a/drivers/net/dsa/mv88e6xxx/chip.c >> +++ b/drivers/net/dsa/mv88e6xxx/chip.c >> @@ -1381,28 +1381,27 @@ static int mv88e6xxx_set_mac_eee(struct = dsa_switch *ds, int port, >> /* Mask of the local ports allowed to receive frames from a given = fabric port */ >> static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, = int port) >> { >> + struct dsa_port *dp =3D NULL, *iter, *other_dp; >> struct dsa_switch *ds =3D chip->ds; >> struct dsa_switch_tree *dst =3D ds->dst; >> - struct dsa_port *dp, *other_dp; >> - bool found =3D false; >> u16 pvlan; >>=20 >> /* dev is a physical switch */ >> if (dev <=3D dst->last_switch) { >> - list_for_each_entry(dp, &dst->ports, list) { >> - if (dp->ds->index =3D=3D dev && dp->index =3D=3D = port) { >> - /* dp might be a DSA link or a user = port, so it >> + list_for_each_entry(iter, &dst->ports, list) { >> + if (iter->ds->index =3D=3D dev && iter->index =3D=3D= port) { >> + /* iter might be a DSA link or a user = port, so it >> * might or might not have a bridge. >> - * Use the "found" variable for both = cases. >> + * Set the "dp" variable for both cases. >> */ >> - found =3D true; >> + dp =3D iter; >> break; >> } >> } >> /* dev is a virtual bridge */ >> } else { >> - list_for_each_entry(dp, &dst->ports, list) { >> - unsigned int bridge_num =3D = dsa_port_bridge_num_get(dp); >> + list_for_each_entry(iter, &dst->ports, list) { >> + unsigned int bridge_num =3D = dsa_port_bridge_num_get(iter); >>=20 >> if (!bridge_num) >> continue; >> @@ -1410,13 +1409,13 @@ static u16 mv88e6xxx_port_vlan(struct = mv88e6xxx_chip *chip, int dev, int port) >> if (bridge_num + dst->last_switch !=3D dev) >> continue; >>=20 >> - found =3D true; >> + dp =3D iter; >> break; >> } >> } >>=20 >> /* Prevent frames from unknown switch or virtual bridge */ >> - if (!found) >> + if (!dp) >> return 0; >>=20 >> /* Frames from DSA links and CPU ports can egress any local port = */ >> --=20 >> 2.25.1 >>=20 >=20 > Let's try to not make convoluted code worse. Do the following 2 = patches > achieve what you are looking for? Originally I had a single patch = (what > is now 2/2) but I figured it would be cleaner to break out the = unrelated > change into what is now 1/2. I do agree with not making convoluted code worse, but I was reluctant = with e.g. introducing new functions for this because others essentially have the opposite opinion on this. I however like solving it that way, it makes it a lot cleaner. >=20 > If you want I can submit these changes separately. Sure if you want to submit them separately, go ahead. Otherwise I can integrate it into a v2, whatever you prefer essentially. >=20 > -----------------------------[ cut here ]----------------------------- > =46rom 2d84ecd87566b1535a04526b4ebb2764e764625f Mon Sep 17 00:00:00 = 2001 > From: Vladimir Oltean > Date: Fri, 8 Apr 2022 15:15:30 +0300 > Subject: [PATCH 1/2] net: dsa: mv88e6xxx: remove redundant check in > mv88e6xxx_port_vlan() >=20 > We know that "dev > dst->last_switch" in the "else" block. > In other words, that "dev - dst->last_switch" is > 0. >=20 > dsa_port_bridge_num_get(dp) can be 0, but the check > "if (bridge_num + dst->last_switch !=3D dev) continue", rewritten as > "if (bridge_num !=3D dev - dst->last_switch) continue", aka > "if (bridge_num !=3D something which cannot be 0) continue", > makes it redundant to have the extra "if (!bridge_num) continue" = logic, > since a bridge_num of zero would have been skipped anyway. >=20 > Signed-off-by: Vladimir Oltean > --- > drivers/net/dsa/mv88e6xxx/chip.c | 3 --- > 1 file changed, 3 deletions(-) >=20 > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c = b/drivers/net/dsa/mv88e6xxx/chip.c > index 64f4fdd02902..b3aa0e5bc842 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -1404,9 +1404,6 @@ static u16 mv88e6xxx_port_vlan(struct = mv88e6xxx_chip *chip, int dev, int port) > list_for_each_entry(dp, &dst->ports, list) { > unsigned int bridge_num =3D = dsa_port_bridge_num_get(dp); >=20 > - if (!bridge_num) > - continue; > - > if (bridge_num + dst->last_switch !=3D dev) > continue; >=20 > -----------------------------[ cut here ]----------------------------- >=20 > -----------------------------[ cut here ]----------------------------- > =46rom dabafdbe38b408f7c563ad91fc6e57791055fed7 Mon Sep 17 00:00:00 = 2001 > From: Vladimir Oltean > Date: Fri, 8 Apr 2022 14:57:45 +0300 > Subject: [PATCH 2/2] net: dsa: mv88e6xxx: refactor = mv88e6xxx_port_vlan() >=20 > To avoid bugs and speculative execution exploits due to type-confused > pointers at the end of a list_for_each_entry() loop, one measure is to > restrict code to not use the iterator variable outside the loop block. >=20 > In the case of mv88e6xxx_port_vlan(), this isn't a problem, as we = never > let the loops exit through "natural causes" anyway, by using a "found" > variable and then using the last "dp" iterator prior to the break, = which > is a safe thing to do. >=20 > Nonetheless, with the expected new syntax, this pattern will no longer > be possible. >=20 > Profit off of the occasion and break the two port finding methods into > smaller sub-functions. Somehow, returning a copy of the iterator = pointer > is still accepted. >=20 > This change makes it redundant to have a "bool found", since the "dp" > from mv88e6xxx_port_vlan() now holds NULL if we haven't found what we > were looking for. >=20 > Signed-off-by: Vladimir Oltean > --- > drivers/net/dsa/mv88e6xxx/chip.c | 54 ++++++++++++++++++-------------- > 1 file changed, 31 insertions(+), 23 deletions(-) >=20 > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c = b/drivers/net/dsa/mv88e6xxx/chip.c > index b3aa0e5bc842..1f35e89053e6 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -1378,42 +1378,50 @@ static int mv88e6xxx_set_mac_eee(struct = dsa_switch *ds, int port, > return 0; > } >=20 > +static struct dsa_port *mv88e6xxx_find_port(struct dsa_switch_tree = *dst, > + int sw_index, int port) > +{ > + struct dsa_port *dp; > + > + list_for_each_entry(dp, &dst->ports, list) > + if (dp->ds->index =3D=3D sw_index && dp->index =3D=3D = port) > + return dp; > + > + return NULL; > +} > + > +static struct dsa_port * > +mv88e6xxx_find_port_by_bridge_num(struct dsa_switch_tree *dst, > + unsigned int bridge_num) > +{ > + struct dsa_port *dp; > + > + list_for_each_entry(dp, &dst->ports, list) > + if (dsa_port_bridge_num_get(dp) =3D=3D bridge_num) > + return dp; > + > + return NULL; > +} > + > /* Mask of the local ports allowed to receive frames from a given = fabric port */ > static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, = int port) > { > struct dsa_switch *ds =3D chip->ds; > struct dsa_switch_tree *dst =3D ds->dst; > struct dsa_port *dp, *other_dp; > - bool found =3D false; > u16 pvlan; >=20 > - /* dev is a physical switch */ > if (dev <=3D dst->last_switch) { > - list_for_each_entry(dp, &dst->ports, list) { > - if (dp->ds->index =3D=3D dev && dp->index =3D=3D = port) { > - /* dp might be a DSA link or a user = port, so it > - * might or might not have a bridge. > - * Use the "found" variable for both = cases. > - */ > - found =3D true; > - break; > - } > - } > - /* dev is a virtual bridge */ > + /* dev is a physical switch */ > + dp =3D mv88e6xxx_find_port(dst, dev, port); > } else { > - list_for_each_entry(dp, &dst->ports, list) { > - unsigned int bridge_num =3D = dsa_port_bridge_num_get(dp); > - > - if (bridge_num + dst->last_switch !=3D dev) > - continue; > - > - found =3D true; > - break; > - } > + /* dev is a virtual bridge */ > + dp =3D mv88e6xxx_find_port_by_bridge_num(dst, > + dev - = dst->last_switch); > } >=20 > /* Prevent frames from unknown switch or virtual bridge */ > - if (!found) > + if (!dp) > return 0; >=20 > /* Frames from DSA links and CPU ports can egress any local port = */ > -----------------------------[ cut here ]----------------------------- Thanks, Jakob 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6A010C433EF for ; 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Fri, 08 Apr 2022 16:44:04 -0700 (PDT) Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.80.82.1.1\)) Subject: Re: [PATCH net-next 03/15] net: dsa: mv88e6xxx: Replace usage of found with dedicated iterator From: Jakob Koschel In-Reply-To: <20220408123101.p33jpynhqo67hebe@skbuf> Date: Sat, 9 Apr 2022 01:44:00 +0200 Cc: "David S. Miller" , Jakub Kicinski , Paolo Abeni , Andrew Lunn , Vivien Didelot , Florian Fainelli , Lars Povlsen , Steen Hegelund , UNGLinuxDriver@microchip.com, Ariel Elior , Manish Chopra , Edward Cree , Martin Habets , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Jiri Pirko , Casper Andersson , Bjarni Jonasson , Colin Ian King , Michael Walle , Christophe JAILLET , Arnd Bergmann , Eric Dumazet , Di Zhu , Xu Wang , Netdev , LKML , Linux ARM , linuxppc-dev , Mike Rapoport , Brian Johannesmeyer , Cristiano Giuffrida , "Bos, H.J." Message-Id: References: <20220407102900.3086255-1-jakobkoschel@gmail.com> <20220407102900.3086255-4-jakobkoschel@gmail.com> <20220408123101.p33jpynhqo67hebe@skbuf> To: Vladimir Oltean X-Mailer: Apple Mail (2.3696.80.82.1.1) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220408_164407_668377_29DF8905 X-CRM114-Status: GOOD ( 51.55 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Vladimir, > On 8. Apr 2022, at 14:31, Vladimir Oltean wrote: > > Hi Jakob, > > On Thu, Apr 07, 2022 at 12:28:48PM +0200, Jakob Koschel wrote: >> To move the list iterator variable into the list_for_each_entry_*() >> macro in the future it should be avoided to use the list iterator >> variable after the loop body. >> >> To *never* use the list iterator variable after the loop it was >> concluded to use a separate iterator variable instead of a >> found boolean [1]. >> >> This removes the need to use a found variable and simply checking if >> the variable was set, can determine if the break/goto was hit. >> >> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1] >> Signed-off-by: Jakob Koschel >> --- >> drivers/net/dsa/mv88e6xxx/chip.c | 21 ++++++++++----------- >> 1 file changed, 10 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c >> index 64f4fdd02902..f254f537c357 100644 >> --- a/drivers/net/dsa/mv88e6xxx/chip.c >> +++ b/drivers/net/dsa/mv88e6xxx/chip.c >> @@ -1381,28 +1381,27 @@ static int mv88e6xxx_set_mac_eee(struct dsa_switch *ds, int port, >> /* Mask of the local ports allowed to receive frames from a given fabric port */ >> static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port) >> { >> + struct dsa_port *dp = NULL, *iter, *other_dp; >> struct dsa_switch *ds = chip->ds; >> struct dsa_switch_tree *dst = ds->dst; >> - struct dsa_port *dp, *other_dp; >> - bool found = false; >> u16 pvlan; >> >> /* dev is a physical switch */ >> if (dev <= dst->last_switch) { >> - list_for_each_entry(dp, &dst->ports, list) { >> - if (dp->ds->index == dev && dp->index == port) { >> - /* dp might be a DSA link or a user port, so it >> + list_for_each_entry(iter, &dst->ports, list) { >> + if (iter->ds->index == dev && iter->index == port) { >> + /* iter might be a DSA link or a user port, so it >> * might or might not have a bridge. >> - * Use the "found" variable for both cases. >> + * Set the "dp" variable for both cases. >> */ >> - found = true; >> + dp = iter; >> break; >> } >> } >> /* dev is a virtual bridge */ >> } else { >> - list_for_each_entry(dp, &dst->ports, list) { >> - unsigned int bridge_num = dsa_port_bridge_num_get(dp); >> + list_for_each_entry(iter, &dst->ports, list) { >> + unsigned int bridge_num = dsa_port_bridge_num_get(iter); >> >> if (!bridge_num) >> continue; >> @@ -1410,13 +1409,13 @@ static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port) >> if (bridge_num + dst->last_switch != dev) >> continue; >> >> - found = true; >> + dp = iter; >> break; >> } >> } >> >> /* Prevent frames from unknown switch or virtual bridge */ >> - if (!found) >> + if (!dp) >> return 0; >> >> /* Frames from DSA links and CPU ports can egress any local port */ >> -- >> 2.25.1 >> > > Let's try to not make convoluted code worse. Do the following 2 patches > achieve what you are looking for? Originally I had a single patch (what > is now 2/2) but I figured it would be cleaner to break out the unrelated > change into what is now 1/2. I do agree with not making convoluted code worse, but I was reluctant with e.g. introducing new functions for this because others essentially have the opposite opinion on this. I however like solving it that way, it makes it a lot cleaner. > > If you want I can submit these changes separately. Sure if you want to submit them separately, go ahead. Otherwise I can integrate it into a v2, whatever you prefer essentially. > > -----------------------------[ cut here ]----------------------------- > From 2d84ecd87566b1535a04526b4ebb2764e764625f Mon Sep 17 00:00:00 2001 > From: Vladimir Oltean > Date: Fri, 8 Apr 2022 15:15:30 +0300 > Subject: [PATCH 1/2] net: dsa: mv88e6xxx: remove redundant check in > mv88e6xxx_port_vlan() > > We know that "dev > dst->last_switch" in the "else" block. > In other words, that "dev - dst->last_switch" is > 0. > > dsa_port_bridge_num_get(dp) can be 0, but the check > "if (bridge_num + dst->last_switch != dev) continue", rewritten as > "if (bridge_num != dev - dst->last_switch) continue", aka > "if (bridge_num != something which cannot be 0) continue", > makes it redundant to have the extra "if (!bridge_num) continue" logic, > since a bridge_num of zero would have been skipped anyway. > > Signed-off-by: Vladimir Oltean > --- > drivers/net/dsa/mv88e6xxx/chip.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c > index 64f4fdd02902..b3aa0e5bc842 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -1404,9 +1404,6 @@ static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port) > list_for_each_entry(dp, &dst->ports, list) { > unsigned int bridge_num = dsa_port_bridge_num_get(dp); > > - if (!bridge_num) > - continue; > - > if (bridge_num + dst->last_switch != dev) > continue; > > -----------------------------[ cut here ]----------------------------- > > -----------------------------[ cut here ]----------------------------- > From dabafdbe38b408f7c563ad91fc6e57791055fed7 Mon Sep 17 00:00:00 2001 > From: Vladimir Oltean > Date: Fri, 8 Apr 2022 14:57:45 +0300 > Subject: [PATCH 2/2] net: dsa: mv88e6xxx: refactor mv88e6xxx_port_vlan() > > To avoid bugs and speculative execution exploits due to type-confused > pointers at the end of a list_for_each_entry() loop, one measure is to > restrict code to not use the iterator variable outside the loop block. > > In the case of mv88e6xxx_port_vlan(), this isn't a problem, as we never > let the loops exit through "natural causes" anyway, by using a "found" > variable and then using the last "dp" iterator prior to the break, which > is a safe thing to do. > > Nonetheless, with the expected new syntax, this pattern will no longer > be possible. > > Profit off of the occasion and break the two port finding methods into > smaller sub-functions. Somehow, returning a copy of the iterator pointer > is still accepted. > > This change makes it redundant to have a "bool found", since the "dp" > from mv88e6xxx_port_vlan() now holds NULL if we haven't found what we > were looking for. > > Signed-off-by: Vladimir Oltean > --- > drivers/net/dsa/mv88e6xxx/chip.c | 54 ++++++++++++++++++-------------- > 1 file changed, 31 insertions(+), 23 deletions(-) > > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c > index b3aa0e5bc842..1f35e89053e6 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -1378,42 +1378,50 @@ static int mv88e6xxx_set_mac_eee(struct dsa_switch *ds, int port, > return 0; > } > > +static struct dsa_port *mv88e6xxx_find_port(struct dsa_switch_tree *dst, > + int sw_index, int port) > +{ > + struct dsa_port *dp; > + > + list_for_each_entry(dp, &dst->ports, list) > + if (dp->ds->index == sw_index && dp->index == port) > + return dp; > + > + return NULL; > +} > + > +static struct dsa_port * > +mv88e6xxx_find_port_by_bridge_num(struct dsa_switch_tree *dst, > + unsigned int bridge_num) > +{ > + struct dsa_port *dp; > + > + list_for_each_entry(dp, &dst->ports, list) > + if (dsa_port_bridge_num_get(dp) == bridge_num) > + return dp; > + > + return NULL; > +} > + > /* Mask of the local ports allowed to receive frames from a given fabric port */ > static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port) > { > struct dsa_switch *ds = chip->ds; > struct dsa_switch_tree *dst = ds->dst; > struct dsa_port *dp, *other_dp; > - bool found = false; > u16 pvlan; > > - /* dev is a physical switch */ > if (dev <= dst->last_switch) { > - list_for_each_entry(dp, &dst->ports, list) { > - if (dp->ds->index == dev && dp->index == port) { > - /* dp might be a DSA link or a user port, so it > - * might or might not have a bridge. > - * Use the "found" variable for both cases. > - */ > - found = true; > - break; > - } > - } > - /* dev is a virtual bridge */ > + /* dev is a physical switch */ > + dp = mv88e6xxx_find_port(dst, dev, port); > } else { > - list_for_each_entry(dp, &dst->ports, list) { > - unsigned int bridge_num = dsa_port_bridge_num_get(dp); > - > - if (bridge_num + dst->last_switch != dev) > - continue; > - > - found = true; > - break; > - } > + /* dev is a virtual bridge */ > + dp = mv88e6xxx_find_port_by_bridge_num(dst, > + dev - dst->last_switch); > } > > /* Prevent frames from unknown switch or virtual bridge */ > - if (!found) > + if (!dp) > return 0; > > /* Frames from DSA links and CPU ports can egress any local port */ > -----------------------------[ cut here ]----------------------------- Thanks, Jakob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel