linux-kernel - Re: Re: [PATCH 2/2] ax25: add refcount in ax25

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Date:   Tue, 1 Feb 2022 14:26:23 +0800 (GMT+08:00)
From:   周多明 <22021233@....edu.cn>
To:     "Dan Carpenter" <dan.carpenter@...cle.com>
Cc:     linux-hams@...r.kernel.org, jreuter@...na.de, ralf@...ux-mips.org,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH 2/2] ax25: add refcount in ax25_dev to avoid UAF
 bugs

Thank you very much for your time and pointing out problems in my patch.

The decrement of ax25_bind() is in ax25_kill_by_device(). If we don't
call ax25_bind() before ax25_kill_by_device(), the ax25_list will be
empty and ax25_dev_put() in ax25_kill_by_device() will not execute.

> @@ -91,6 +91,7 @@ static void ax25_kill_by_device(struct net_device *dev)
>  			spin_unlock_bh(&ax25_list_lock);
>  			lock_sock(sk);
>  			s->ax25_dev = NULL;
> +			ax25_dev_put(ax25_dev);
>  			release_sock(sk);
>  			ax25_disconnect(s, ENETUNREACH);
>  			spin_lock_bh(&ax25_list_lock);

I will send the improved patch as soon as possible.

Best wishes,
Duoming Zhou