netdev - Re: [PATCH] rtlwifi: Fix null-pointer dereferences in error handling code of rtl_pci

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Date:   Wed, 29 May 2019 10:48:21 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Jia-Ju Bai <baijiaju1990@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>
Cc:     pkshih@...ltek.com, davem@...emloft.net,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtlwifi: Fix null-pointer dereferences in error handling
 code of rtl_pci_probe()

On 5/29/19 5:30 AM, Jia-Ju Bai wrote:
> 
> 
> On 2019/5/28 21:00, Larry Finger wrote:
>> On 5/28/19 6:55 AM, Kalle Valo wrote:
>>> Jia-Ju Bai <baijiaju1990@...il.com> wrote:
>>>
>>>> *BUG 1:
>>>> In rtl_pci_probe(), when rtlpriv->cfg->ops->init_sw_vars() fails,
>>>> rtl_deinit_core() in the error handling code is executed.
>>>> rtl_deinit_core() calls rtl_free_entries_from_scan_list(), which uses
>>>> rtlpriv->scan_list.list in list_for_each_entry_safe(), but it has been
>>>> initialized. Thus a null-pointer dereference occurs.
>>>> The reason is that rtlpriv->scan_list.list is initialized by
>>>> INIT_LIST_HEAD() in rtl_init_core(), which has not been called.
>>>>
>>>> To fix this bug, rtl_deinit_core() should not be called when
>>>> rtlpriv->cfg->ops->init_sw_vars() fails.
>>>>
>>>> *BUG 2:
>>>> In rtl_pci_probe(), rtl_init_core() can fail when rtl_regd_init() in
>>>> this function fails, and rtlpriv->scan_list.list has not been
>>>> initialized by INIT_LIST_HEAD(). Then, rtl_deinit_core() in the error
>>>> handling code of rtl_pci_probe() is executed. Finally, a null-pointer
>>>> dereference occurs due to the same reason of the above bug.
>>>>
>>>> To fix this bug, the initialization of lists in rtl_init_core() are
>>>> performed before the call to rtl_regd_init().
>>>>
>>>> These bugs are found by a runtime fuzzing tool named FIZZER written by
>>>> us.
>>>>
>>>> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
>>>
>>> Ping & Larry, is this ok to take?
>>>
>>
>> Kalle,
>>
>> Not at the moment. In reviewing the code, I was unable to see how this 
>> situation could develop, and his backtrace did not mention any rtlwifi code. 
>> For that reason, I asked him to add printk stat4ements to show the last part 
>> of rtl_pci that executed correctly. In 
>> https://marc.info/?l=linux-wireless&m=155788322631134&w=2, he promised to do 
>> that, but I have not seen the result.
>>
> 
> Hi Larry,
> 
> This patch is not related to the message you mentioned.
> That message is about an occasional crash that I reported.
> That crash occurred when request_irq() in rtl_pci_intr_mode_legacy() in 
> rtl_pci_intr_mode_decide() fails.
> I have added printk statements and try to reproduce and debug that crash, but 
> that crash does not always occur, and I still do not know the root cause of that 
> crash.
> 
> The null-pointer dereferences fixed by this patch are different from that crash, 
> and they always occur when the related functions fail.
> So please review these null-pointer dereferences, thanks :)
> 
> 
> Best wishes,
> Jia-Ju Bai

Sorry if I got confused. Kalle has dropped this patch, thus you will need to 
submit a new version.

Larry