netdev - Re: [PATCH net] tcp: correct read of TFO keys on big endian systems

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Message-Id: <20200810.121306.1528219950635067954.davem@davemloft.net>
Date:   Mon, 10 Aug 2020 12:13:06 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jbaron@...mai.com
Cc:     netdev@...r.kernel.org, colin.king@...onical.com,
        ard.biesheuvel@...aro.org, edumazet@...gle.com
Subject: Re: [PATCH net] tcp: correct read of TFO keys on big endian systems

From: Jason Baron <jbaron@...mai.com>
Date: Mon, 10 Aug 2020 13:38:39 -0400

> When TFO keys are read back on big endian systems either via the global
> sysctl interface or via getsockopt() using TCP_FASTOPEN_KEY, the values
> don't match what was written.
> 
> For example, on s390x:
> 
> # echo "1-2-3-4" > /proc/sys/net/ipv4/tcp_fastopen_key
> # cat /proc/sys/net/ipv4/tcp_fastopen_key
> 02000000-01000000-04000000-03000000
> 
> Instead of:
> 
> # cat /proc/sys/net/ipv4/tcp_fastopen_key
> 00000001-00000002-00000003-00000004
> 
> Fix this by converting to the correct endianness on read. This was
> reported by Colin Ian King when running the 'tcp_fastopen_backup_key' net
> selftest on s390x, which depends on the read value matching what was
> written. I've confirmed that the test now passes on big and little endian
> systems.
> 
> Signed-off-by: Jason Baron <jbaron@...mai.com>
> Fixes: 438ac88009bc ("net: fastopen: robustness and endianness fixes for SipHash")
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Reported-and-tested-by: Colin Ian King <colin.king@...onical.com>

Applied, thanks Jason.