netdev - Re: [PATCH net-next v4 06/18] net: dsa: mv88e6xxx: refactor mv88e6xxx_port

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Date:   Sat, 16 Apr 2022 12:38:35 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jakob Koschel <jakobkoschel@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Jiri Pirko <jiri@...nulli.us>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Casper Andersson <casper.casan@...il.com>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Arnd Bergmann <arnd@...db.de>,
        Colin Ian King <colin.king@...el.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Xu Wang <vulab@...as.ac.cn>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, bpf@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH net-next v4 06/18] net: dsa: mv88e6xxx: refactor
 mv88e6xxx_port_vlan()



On 4/15/2022 5:29 AM, Jakob Koschel wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> 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 <vladimir.oltean@....com>
> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian