linux-kernel - Re: [PATCH net] net/smc: fix listen processing for SMC-Rv2

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Date:   Mon, 23 May 2022 13:19:04 +0200
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     liuyacan@...p.netease.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Cc:     linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ubraun@...ux.ibm.com
Subject: Re: [PATCH net] net/smc: fix listen processing for SMC-Rv2

On 23/05/2022 07:50, liuyacan@...p.netease.com wrote:
> From: liuyacan <liuyacan@...p.netease.com>
> 
> In the process of checking whether RDMAv2 is available, the current
> implementation first sets ini->smcrv2.ib_dev_v2, and then allocates
> smc buf desc, but the latter may fail. Unfortunately, the caller
> will only check the former. In this case, a NULL pointer reference
> will occur in smc_clc_send_confirm_accept() when accessing
> conn->rmb_desc.
> 
> This patch does two things:
> 1. Use the return code to determine whether V2 is available.
> 2. If the return code is NODEV, continue to check whether V1 is
> available.
> 
> Fixes: e49300a6bf62 ("net/smc: add listen processing for SMC-Rv2")
> Signed-off-by: liuyacan <liuyacan@...p.netease.com>
> ---

I am not happy with this patch. You are right that this is a problem,
but the fix should be much simpler: set ini->smcrv2.ib_dev_v2 = NULL in
smc_find_rdma_v2_device_serv() after the not_found label, just like it is
done in a similar way for the ISM device in smc_find_ism_v1_device_serv().

Your patch changes many more things, and beside that you eliminated the calls 
to smc_find_ism_store_rc() completely, which is not correct.

Since your patch was already applied (btw. 3:20 hours after you submitted it),
please revert it and resend. Thank you.