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

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Date:   Wed, 29 May 2019 18:30:36 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Larry Finger <Larry.Finger@...inger.net>,
        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 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