netdev - Re: [PATCH] net/smc: replace strncpy with strscpy for ib

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Message-ID: <90577486-5f7f-4c62-ae65-07e7808837f4@linux.ibm.com>
Date: Mon, 15 Sep 2025 15:14:10 +0530
From: Mahanta Jambigi <mjambigi@...ux.ibm.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Kriish Sharma <kriish.sharma2006@...il.com>, alibuda@...ux.alibaba.com,
        dust.li@...ux.alibaba.com, sidraya@...ux.ibm.com, wenjia@...ux.ibm.com,
        tonylu@...ux.alibaba.com, guwen@...ux.alibaba.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        horms@...nel.org, linux-rdma@...r.kernel.org,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] net/smc: replace strncpy with strscpy for ib_name



On 15/09/25 1:32 pm, Leon Romanovsky wrote:
> On Mon, Sep 15, 2025 at 12:24:16PM +0530, Mahanta Jambigi wrote:
>> On 12/09/25 2:37 pm, Leon Romanovsky wrote:
>>> On Fri, Sep 12, 2025 at 01:18:52PM +0530, Mahanta Jambigi wrote:
>>>> On 10/09/25 3:31 pm, Leon Romanovsky wrote:
>>>>>> --- a/net/smc/smc_pnet.c
>>>>>> +++ b/net/smc/smc_pnet.c
>>>>>> @@ -450,7 +450,7 @@ static int smc_pnet_add_ib(struct smc_pnettable *pnettable, char *ib_name,
>>>>>>  		return -ENOMEM;
>>>>>>  	new_pe->type = SMC_PNET_IB;
>>>>>>  	memcpy(new_pe->pnet_name, pnet_name, SMC_MAX_PNETID_LEN);
>>>>>> -	strncpy(new_pe->ib_name, ib_name, IB_DEVICE_NAME_MAX);
>>>>>> +	strscpy(new_pe->ib_name, ib_name);
>>>>>
>>>>> It is worth to mention that caching ib_name is wrong as IB/core provides
>>>>> IB device rename functionality.
>>>>
>>>> In our case we hit this code path where we pass *PCI_ID*
>>>> as the *ib_name* using *smc_pnet* tool(smc_pnet -a <pnet_name> -D
>>>> <PCI_ID>). I believe PCI_ID will not change, so caching it here is fine.
>>>
>>> If I remember, you are reporting that cached ib_name through netlink much later.
>>>
>>> The caching itself is not an issue, but incorrect reported name can be seen as
>>> a wrong thing to do.
>>
>> In what case we can see this incorrect reported name, could you please
>> elaborate.
> 
> Did you open net/smc/smc_pnet.c?

Yes, I have gone through it focusing on *ib_name* usage.

> 
> Everything that uses ib_name in that file is incorrect.
> 
> From glance look:
> 1. smc_pnet_find_ib() returns completely random results if device is
> renamed in parallel.

I agree. Currently we are *not* handling the change of IB device names &
when that happens the cached *ib_name* doesn't match anymore with the
changed ib_name. We are looking into this internally.