netdev - Re: [PATCH v2 net 09/12] net: Fix data-races around sysctl

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Message-ID: <6dddf3f2-40c1-a08b-ec0e-c4feafcad118@tessares.net>
Date:   Sat, 9 Jul 2022 11:11:47 +0200
From:   Matthieu Baerts <matthieu.baerts@...sares.net>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>
Cc:     Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        MPTCP Upstream <mptcp@...ts.linux.dev>
Subject: Re: [PATCH v2 net 09/12] net: Fix data-races around sysctl_mem.

Hello,

On 07/07/2022 01:40, Kuniyuki Iwashima wrote:
> While reading .sysctl_mem, it can be changed concurrently.
> So, we need to add READ_ONCE() to avoid data-races.

FYI, we got a small conflict when merging -net in net-next in the MPTCP
tree due to this patch applied in -net:

  310731e2f161 ("net: Fix data-races around sysctl_mem.")

and this one from net-next:

  e70f3c701276 ("Revert "net: set SK_MEM_QUANTUM to 4096"")

The conflict has been resolved on our side[1] and the resolution we
suggest is attached to this email.

I'm sharing this thinking it can help others but if it only creates
noise, please tell me! :)

Cheers,
Matt

[1] https://github.com/multipath-tcp/mptcp_net-next/commit/b01bda9d0fe6
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View attachment "b01bda9d0fe6.patch" of type "text/x-patch" (836 bytes)