linux-kernel - Re: [PATCH v2] cw1200: fix incorrect check to determine if no element is found in list

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Date:   Wed, 6 Apr 2022 10:02:31 -0700
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Kalle Valo <kvalo@...nel.org>,
        Xiaomeng Tong <xiam0nd.tong@...il.com>
CC:     <pizza@...ftnet.org>, <davem@...emloft.net>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <linville@...driver.com>,
        <linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <jakobkoschel@...il.com>
Subject: Re: [PATCH v2] cw1200: fix incorrect check to determine if no element
 is found in list

On 4/6/2022 4:32 AM, Kalle Valo wrote:
> Xiaomeng Tong <xiam0nd.tong@...il.com> wrote:
> 
>> The bug is here: "} else if (item) {".
>>
>> The list iterator value will *always* be set and non-NULL by
>> list_for_each_entry(), so it is incorrect to assume that the iterator
>> value will be NULL if the list is empty or no element is found in list.
>>
>> Use a new value 'iter' as the list iterator, while use the old value
>> 'item' as a dedicated pointer to point to the found element, which
>> 1. can fix this bug, due to now 'item' is NULL only if it's not found.
>> 2. do not need to change all the uses of 'item' after the loop.
>> 3. can also limit the scope of the list iterator 'iter' *only inside*
>>     the traversal loop by simply declaring 'iter' inside the loop in the
>>     future, as usage of the iterator outside of the list_for_each_entry
>>     is considered harmful. https://lkml.org/lkml/2022/2/17/1032
>>
>> Fixes: a910e4a94f692 ("cw1200: add driver for the ST-E CW1100 & CW1200 WLAN chipsets")
>> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
> 
> Can someone review this, please?
> 

Reviewed-by: Jeff Johnson <quic_jjohnson@...cinc.com>