Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] intel_th: avoid double free in error flow
To:     Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc:     zhiche.yy@alibaba-inc.com, xlpang@linux.alibaba.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
References: <20191119173447.2454-1-wenyang@linux.alibaba.com>
 <87y2wad7e5.fsf@ashishki-desk.ger.corp.intel.com>
 <7e2a501f-955a-5bd1-f70d-ad69e7223981@linux.alibaba.com>
 <87v9red5x7.fsf@ashishki-desk.ger.corp.intel.com>
From:   Wen Yang <wenyang@linux.alibaba.com>
Message-ID: <08c38d22-196d-a12e-f3e1-bc67f5912cb5@linux.alibaba.com>
Date:   Wed, 20 Nov 2019 21:46:00 +0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0)
 Gecko/20100101 Thunderbird/68.1.1
MIME-Version: 1.0
In-Reply-To: <87v9red5x7.fsf@ashishki-desk.ger.corp.intel.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2019/11/20 9:38 下午, Alexander Shishkin wrote:
> Wen Yang <wenyang@linux.alibaba.com> writes:
>
>> Another example after a few lines lower:
>>
>>           err = device_add(&thdev->dev);
>>
>>           if (err) {
>>                    put_device(&thdev->dev);
>>                    goto fail_free_res;
>>
>>            }
>>
>> device_add() has increased the reference count,
>>
>> so when it returns an error, an additional call to put_device()
>>
>> is needed here to reduce the reference count.
>>
>> So the code in this place is correct.
> No, device_add() drops its own extra reference in case of error (as it
> should), so in "if (err) ..." branch we still only have just one
> reference before it goes free.
>
> Regards,
> --
> Alex


Well, ok, you are right.

We just checked the code and device_add() does release the reference count.

Thank you.


--

Regards,

Wen