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Message-ID: <CAM_iQpXoPGFj=ey7_aYKhhfPdL1SMxQj=adydxVYqwPJhBOSpg@mail.gmail.com> Date: Wed, 23 Jan 2019 15:25:53 -0800 From: Cong Wang <xiyou.wangcong@...il.com> To: Eric Dumazet <edumazet@...gle.com> Cc: "David S . Miller" <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, Eric Dumazet <eric.dumazet@...il.com>, Ralf Baechle <ralf@...ux-mips.org>, syzbot <syzkaller@...glegroups.com> Subject: Re: [PATCH net] ax25: fix possible use-after-free On Tue, Jan 22, 2019 at 10:41 AM 'Eric Dumazet' via syzkaller <syzkaller@...glegroups.com> wrote: > > syzbot found that ax25 routes where not properly protected > against concurrent use [1]. > > In this particular report the bug happened while > copying ax25->digipeat. > > Fix this problem by making sure we call ax25_get_route() > while ax25_route_lock is held, so that no modification > could happen while using the route. ax25_route_lock_use() is a read lock, so two ax25_rt_autobind() could still enter the same critical section? > > The current two ax25_get_route() callers do not sleep, > so this change should be fine. > > Once we do that, ax25_get_route() no longer needs to > grab a reference on the found route. . After your patch, ax25_hold_route() has no callers while ax25_put_route() still does. Is ->refcount always 1? Thanks.
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