linux-kernel - Re: [PATCH v0] mctp: fix netdev reference bug

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Message-ID: <48d1c4f9.13e3e.17fb9f5bc59.Coremail.linma@zju.edu.cn>
Date:   Thu, 24 Mar 2022 11:26:03 +0800 (GMT+08:00)
From:   "Lin Ma" <linma@....edu.cn>
To:     "Matt Johnston" <matt@...econstruct.com.au>
Cc:     jk <jk@...econstruct.com.au>, davem <davem@...emloft.net>,
        kuba <kuba@...nel.org>, pabeni <pabeni@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v0] mctp: fix netdev reference bug

Hi Matt,

Oops, sorry for the false alarm, I found this on mainline kernel and I should checkout net-next before sending the patch.

Regards

>Hi Lin Ma,
>
>On Thu, 2022-03-24 at 10:39 +0800, Lin Ma wrote:
>> In extended addressing mode, function mctp_local_output() fetch netdev
>> through dev_get_by_index_rcu, which won't increase netdev's reference
>> counter. Hence, the reference may underflow when mctp_local_output calls
>> dev_put(), results in possible use after free.
>> 
>> This patch adds dev_hold() to fix the reference bug.
>
>This was already fixed in net-next to increment the refcount in
>__mctp_dev_get() and use mctp_dev_put().
>
>dc121c008491 ("mctp: make __mctp_dev_get() take a refcount hold")
>e297db3eadd7 ("mctp: Fix incorrect netdev unref for extended addr")
>
>Thanks,
>Matt