Date: Tue, 22 Nov 2016 18:22:47 +0100
From: Andre Noll <maan@tuebingen.mpg.de>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Jiri Slaby <jslaby@suse.cz>, Eric Dumazet <edumazet@google.com>,
        Yibin Yang <yibyang@cisco.com>,
        Alexander Duyck <alexander.h.duyck@intel.com>,
        Willem de Bruijn <willemb@google.com>,
        Alexei Starovoitov <ast@kernel.org>,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: Linux 4.4.34
Message-ID: <20161122172247.GB19939@tuebingen.mpg.de>
References: <20161121092855.GA20976@kroah.com>
 <20161122165912.GA19939@tuebingen.mpg.de>
 <20161122170654.GA20022@kroah.com>
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On Tue, Nov 22, 18:06, Greg KH wrote
> On Tue, Nov 22, 2016 at 05:59:12PM +0100, Andre Noll wrote:
> > On Mon, Nov 21, 10:28, Greg KH wrote
> > > I'm announcing the release of the 4.4.34 kernel.
> > >=20
> > > All users of the 4.4 kernel series must upgrade.
> >=20
> > This update broke PXE boot on our 4-way AMD boxes. The kernel panics in
> > eth_type_trans(), presumably during kernel-level IP autoconfiguration,
> > see [1]. Bisection points me at 5c67f947 (net: __skb_flow_dissect()
> > must cap its return value). And indeed, reverting this commit fixes
> > the problem for me.
> >=20
> > Investigation showed that the real problem is not the change in the
> > above commit per se (i.e., capping ->thoff) but the fact that in the
> > success case, where we jump to the "out_good" label, ->thoff is now
> > set *after* ->n_proto and ->ip_proto. I fail to see how order matters
> > here, but it clearly does, since the crash is 100% reproducible,
> > and is fixed by the commit below (on top of v4.4.34).
> >=20
> > Please consider applying something like the patch below for mainline
> > and -stable.
>=20
> If this issue is also the same for Linus's tree, we should cc: netdev so
> that the patch can get into there, right?

Right, but I haven't tested PXE boot on any kernel newer than 4.4.x
so far.  All I can say for sure is that the problematic commit is
also in Linus' tree (called 34fad54c there).

Do you want me to check if mainline is also affected?

Andre
--=20
Max Planck Institute for Developmental Biology
Spemannstra=C3=9Fe 35, 72076 T=C3=BCbingen, Germany. Phone: (+49) 7071 601 =
829
http://people.tuebingen.mpg.de/maan/

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