linux-kernel - Re: [PATCH] net: mdiobus: Fix memory leak in __mdiobus

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Date:   Wed, 29 Sep 2021 10:05:42 +0800
From:   "Xu, Yanfei" <yanfei.xu@...driver.com>
To:     Dongliang Mu <mudongliangabcd@...il.com>,
        "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Pavel Skripkin <paskripkin@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        andrew@...n.ch, hkallweit1@...il.com,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, p.zabel@...gutronix.de,
        syzbot <syzbot+398e7dc692ddbbb4cfec@...kaller.appspotmail.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: mdiobus: Fix memory leak in __mdiobus_register



On 9/28/21 11:48 PM, Dongliang Mu wrote:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
> 
> On Tue, Sep 28, 2021 at 11:41 PM Russell King (Oracle)
> <linux@...linux.org.uk> wrote:
>>
>> On Tue, Sep 28, 2021 at 04:52:07PM +0300, Dan Carpenter wrote:
>>> On Tue, Sep 28, 2021 at 01:58:00PM +0100, Russell King (Oracle) wrote:
>>>>
>>>> This thread seems to be getting out of hand.
>>>
>>> The thread was closed.  We need to revert Yanfei's patch and apply
>>> Pavel's patch.  He's going to resend.
>>>

Sorry for my patch, it is my bad. :( And thanks for Pavel's v2 which 
help to revert mine.

Regards,
Yanfei

>>>> So, I would suggest a simple fix is to set bus->state to
>>>> MDIOBUS_UNREGISTERED immediately _after_ the successful
>>>> device_register().
>>>
>>> Not after.  It has to be set to MDIOBUS_UNREGISTERED if device_register()
>>> fails, otherwise there will still be a leak.
>>
>> Ah yes, you are correct - the device name may not be freed. Also...
>>
>>   * NOTE: _Never_ directly free @dev after calling this function, even
>>   * if it returned an error! Always use put_device() to give up your
>>   * reference instead.
>>
>> So yes, we must set to MDIOBUS_UNREGISTERED even if device_register()
>> fails.
>>
> 
> So we have reached an agreement. Pavel's patch fixes the syzbot link
> [1], other than Yanfei's patch. However, Yanfei's patch also fixes
> another memory link nearby.
> 
> Right?
> 
> [1] https://syzkaller.appspot.com/bug?id=fa99459691911a0369622248e0f4e3285fcedd97
> 
>> --
>> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
>> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!