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Subject: Re: [PATCH] rtlwifi: Fix null-pointer dereferences in error handling
 code of rtl_pci_probe()
To:     Kalle Valo <kvalo@codeaurora.org>,
        Jia-Ju Bai <baijiaju1990@gmail.com>
Cc:     pkshih@realtek.com, davem@davemloft.net,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20190514123439.10524-1-baijiaju1990@gmail.com>
 <20190528115555.301E760F3C@smtp.codeaurora.org>
From:   Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <2658b691-b992-b773-c6cf-85801adc479f@lwfinger.net>
Date:   Tue, 28 May 2019 08:00:24 -0500
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On 5/28/19 6:55 AM, Kalle Valo wrote:
> Jia-Ju Bai <baijiaju1990@gmail.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@gmail.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.

Larry