netdev - Re: [Patch net] ax25: fix a use-after-free in ax25_fillin

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Message-Id: <20181230.140823.1149372994825603009.davem@davemloft.net>
Date:   Sun, 30 Dec 2018 14:08:23 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org
Subject: Re: [Patch net] ax25: fix a use-after-free in ax25_fillin_cb()

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Sat, 29 Dec 2018 13:56:36 -0800

> There are multiple issues here:
> 
> 1. After freeing dev->ax25_ptr, we need to set it to NULL otherwise
>    we may use a dangling pointer.
> 
> 2. There is a race between ax25_setsockopt() and device notifier as
>    reported by syzbot. Close it by holding RTNL lock.
> 
> 3. We need to test if dev->ax25_ptr is NULL before using it.
> 
> Reported-and-tested-by: syzbot+ae6bb869cbed29b29040@...kaller.appspotmail.com
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Applied and queued up for -stable, thanks Cong.