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

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Message-ID: <61ac01e70c293b7e0d378436f7617daaad552fcf.camel@codeconstruct.com.au>
Date:   Thu, 24 Mar 2022 11:17:56 +0800
From:   Matt Johnston <matt@...econstruct.com.au>
To:     Lin Ma <linma@....edu.cn>, jk@...econstruct.com.au,
        davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v0] mctp: fix netdev reference bug

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