netdev - Re: [PATCH] net/mlx5: fix possible stack overflows

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Date: Mon, 19 Feb 2024 20:19:23 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Hamdan Agbariya <hamdani@...dia.com>, Arnd Bergmann <arnd@...db.de>,
 Arnd Bergmann <arnd@...nel.org>, Saeed Mahameed <saeedm@...dia.com>,
 Leon Romanovsky <leon@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Yevgeny Kliteynik <kliteyn@...dia.com>,
 Alex Vesker <valex@...dia.com>, Netdev <netdev@...r.kernel.org>,
 "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net/mlx5: fix possible stack overflows

在 2024/2/19 17:05, Hamdan Agbariya 写道:
>> 在 2024/2/15 16:03, Arnd Bergmann 写道:
>>> On Thu, Feb 15, 2024, at 01:18, Zhu Yanjun wrote:
>>>> 在 2024/2/13 18:08, Arnd Bergmann 写道:
>>>>>     static int
>>>>> -dr_dump_rule_rx_tx(struct seq_file *file, struct mlx5dr_rule_rx_tx
>>>>> *rule_rx_tx,
>>>>> +dr_dump_rule_rx_tx(struct seq_file *file, char *buff,
>>>>> +              struct mlx5dr_rule_rx_tx *rule_rx_tx,
>>>>>                 bool is_rx, const u64 rule_id, u8 format_ver)
>>>>>     {
>>>>>      struct mlx5dr_ste *ste_arr[DR_RULE_MAX_STES +
>>>>> DR_ACTION_MAX_STES]; @@ -533,7 +532,7 @@
>> dr_dump_rule_rx_tx(struct seq_file *file, struct mlx5dr_rule_rx_tx
>> *rule_rx_tx,
>>>>>              return 0;
>>>>>
>>>>>      while (i--) {
>>>>> -           ret = dr_dump_rule_mem(file, ste_arr[i], is_rx, rule_id,
>>>> Before buff is reused, I am not sure whether buff should be firstly
>>>> zeroed or not.
>>> I don't see why it would, but if you want to zero it, that would be a
>>> separate patch that is already needed on the existing code, which
>>> never zeroes its buffers.
>>
>> Sure. I agree with you. In the existing code, the buffers are not zeroed.
>>
>> But to a buffer which is used for several times, it is good to zero it before it is
>> used again.
>>
>> Can you add a new commit with the following?
>>
>> 1). Zero the buffers in the existing code
>>
> 
> No need to zero the buffers, as it does not have any necessity and it will only affect performance.
> Thanks,

Sorry. I can not get your point. Can you explain why no need to zero the 
buffers? Thanks in advance.

> Hamdan
> 
> 
> 
> 
>> 2). Add the zero functionality to your patch

If a buffer is used for many times, is it necessary to zero it before it 
is used again?

Thanks,
Zhu Yanjun

>>
>>   From my perspective, it is good to the whole commit.
>>
>> Please Jason and Leon comment on this.
>>
>> Thanks,
>>
>> Zhu Yanjun
>>
>>>
>>>       Arnd