[MPTCP] Re: Fwd: [martineau:kbuild-mptcp 22/38] subflow.c:undefined reference to `__crypto_memneq'

[Mat Martineau <mathew.j.martineau at linux.intel.com>]

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On Sat, 18 Jan 2020, Florian Westphal wrote:

> ----- Forwarded message from kbuild test robot <lkp(a)intel.com> -----
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/martineau/linux.git kbuild-mptcp
> head:   c4ccdd8177fb3d8123dd294ae93ee2dac1f43f32
> commit: ccd5b6ef8fd4b37a7721231a55482523b07d7ef9 [22/38] mptcp: Add handling of incoming MP_JOIN requests
> config: xtensa-common_defconfig (attached as .config)
> compiler: xtensa-linux-gcc (GCC) 7.5.0
> reproduce:
>        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>        chmod +x ~/bin/make.cross
>        git checkout ccd5b6ef8fd4b37a7721231a55482523b07d7ef9
>        # save the attached .config to linux build tree
>        GCC_VERSION=7.5.0 make.cross ARCH=xtensa
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp(a)intel.com>
>
> All errors (new ones prefixed by >>):
>
>   net/mptcp/subflow.o: In function `subflow_ulp_release':
>>> subflow.c:(.text+0x41c): undefined reference to `__crypto_memneq'
>   net/mptcp/subflow.o: In function `subflow_syn_recv_sock':
>   subflow.c:(.text+0x53a): undefined reference to `__crypto_memneq'
>
> Hmpf.  The .config has CONFIG_CRYPTO=n and then the symbol doesn't
> exist.
>
> So we have two choices:
> - select CRYPTO from Kconfig
> - use plain memcmp as before (might reveal info about key though)
> - copypaste a similar function into mptcp.
>
> What do you think?

I prefer selecting CRYPTO over copy/paste. Plain memcmp does not seem 
suitable.

--
Mat Martineau
Intel