netdev - Re: [PATCH net 0/3] Fix a bug and avoid dangerous usage patterns

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Message-ID: <CA+h21hpB3=SuvYsjsKRKOGDqDcSwG98ExZ2DodwWMUDYQzP+6w@mail.gmail.com>
Date:   Sat, 11 May 2019 23:26:54 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net 0/3] Fix a bug and avoid dangerous usage patterns

On Sat, 11 May 2019 at 23:16, Vladimir Oltean <olteanv@...il.com> wrote:
>
> Making DSA use the sk_buff control block was my idea during the
> 'Traffic-support-for-SJA1105-DSA-driver' patchset, and I had also
> introduced a series of macro helpers that turned out to not be so
> helpful:
>
> 1. DSA_SKB_ZERO() zeroizes the 48-byte skb->cb area, but due to the high
>    performance impact in the hotpath it was only intended to be called
>    from the timestamping path. But it turns out that not zeroizing it
>    has uncovered the reading of an uninitialized member field of
>    DSA_SKB_CB, so in the future just be careful about what needs
>    initialization and remove this macro.
> 2. DSA_SKB_CLONE() contains a flaw in its body definition (originally
>    put there to silence checkpatch.pl) and is unusable at this point
>    (will only cause NPE's when used). So remove it.
> 3. For DSA_SKB_COPY() the same performance considerations apply as above
>    and therefore it's best to prune this function before it reaches a
>    stable kernel and potentially any users.
>
> Vladimir Oltean (3):
>   net: dsa: Initialize DSA_SKB_CB(skb)->deferred_xmit variable
>   net: dsa: Remove dangerous DSA_SKB_CLONE() macro
>   net: dsa: Remove the now unused DSA_SKB_CB_COPY() macro
>
>  include/net/dsa.h | 15 ---------------
>  net/dsa/slave.c   |  2 ++
>  2 files changed, 2 insertions(+), 15 deletions(-)
>
> --
> 2.17.1
>

The title was "Fix a bug and avoid dangerous usage patterns [...around
DSA_SKB_CB]", not sure why it got trimmed.