From: PanBian <bianpan2016@163.com>
To: Ilya Dryomov <idryomov@gmail.com>
Cc: "Yan, Zheng" <zyan@redhat.com>, Sage Weil <sage@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Ceph Development <ceph-devel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] libceph: fix use after free
Date: Wed, 28 Nov 2018 08:22:57 +0800 [thread overview]
Message-ID: <20181128002257.GA38329@bp> (raw)
In-Reply-To: <CAOi1vP8Ff9HLF_v93RwyW4LwQ5jYPWPaZhqBgx9FsxmXH6M4AQ@mail.gmail.com>
On Tue, Nov 27, 2018 at 11:17:26AM +0100, Ilya Dryomov wrote:
> On Tue, Nov 27, 2018 at 10:22 AM Pan Bian <bianpan2016@163.com> wrote:
> >
> > The function ceph_monc_handle_map calls kfree(old) to free the old
> > monitor map, old points to monc->monmap. However, after that, it reads
> > monc->monmap->epoch and passes it to __ceph_monc_got_map. This will
> > result in a use-after-free bug. The patch moves the free operation after
> > the call to __ceph_monc_got_map.
> >
> > Fixes: 82dcabad750 ("libceph: revamp subs code, switch to SUBSCRIBE2 protocol")
> >
> > Signed-off-by: Pan Bian <bianpan2016@163.com>
> > ---
> > V2: correct the format of the tag Fixes
> > ---
> > net/ceph/mon_client.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
> > index 18deb3d..05ef5aa 100644
> > --- a/net/ceph/mon_client.c
> > +++ b/net/ceph/mon_client.c
> > @@ -478,9 +478,10 @@ static void ceph_monc_handle_map(struct ceph_mon_client *monc,
> > }
> >
> > client->monc.monmap = monmap;
>
> monc->monmap is assigned here. It's not obvious, but monc->monmap and
> client->monc.monmap is the same pointer.
>
> > - kfree(old);
> >
> > __ceph_monc_got_map(monc, CEPH_SUB_MONMAP, monc->monmap->epoch);
>
> ceph_monmap_decode() returns the new map, kfree() frees the old map.
> I don't see a use-after-free here.
Got it. Thank you!
Pan
>
> Thanks,
>
> Ilya
prev parent reply other threads:[~2018-11-28 0:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 9:21 [PATCH V2] libceph: fix use after free Pan Bian
2018-11-27 10:17 ` Ilya Dryomov
2018-11-28 0:22 ` PanBian [this message]
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