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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