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Date: Tue, 25 Apr 2017 18:57:25 +0800
From: Honggang LI <honli@redhat.com>
To: Or Gerlitz <gerlitz.or@gmail.com>
Cc: Erez Shitrit <erezsh@mellanox.com>, Doug Ledford <dledford@redhat.com>,
        "Hefty, Sean" <sean.hefty@intel.com>,
        Hal Rosenstock <hal.rosenstock@gmail.com>,
        Paolo Abeni <pabeni@redhat.com>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Linux Netdev List <netdev@vger.kernel.org>
Subject: Re: [PATCH] IB/IPoIB: Check the headroom size
Message-ID: <20170425105725.GA14400@dhcp-13-42.nay.redhat.com>
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On Tue, Apr 25, 2017 at 01:32:59PM +0300, Or Gerlitz wrote:
> On Tue, Apr 25, 2017 at 12:55 PM, Honggang LI <honli@redhat.com> wrote:
> > From: Honggang Li <honli@redhat.com>
> >
> > Minimal hard_header_len set by bond_compute_features is ETH_HLEN, which
> > is smaller than IPOIB_HARD_LEN. ipoib_hard_header should check the
> > size of headroom to avoid skb_under_panic.
> 
> sounds terrible, ipoib bonding is supported since ~2007, thanks for
> reporting on that.
> 
> > [  122.871493] ipoib_hard_header: skb->head= ffff8808179d9400, skb->data= ffff8808179d9420, skb_headroom= 0x20
> > [  123.055400] bond0: Releasing backup interface mthca_ib1
> > [  123.560529] bond_compute_features:1112 bond0 bond_dev->hard_header_len = 14
> > [  123.568822] CPU: 0 PID: 12336 Comm: ifdown-ib Not tainted 4.9.0-debug #1
> 
> did you generate this trace by calling dump_stack or this is existing
> kernel code.

I inserted dump_stack to print this stack for debug.

> 
> > Fixes: fc791b633515 ('IB/ipoib: move back IB LL address into the hard header')
> 
> this is more of WA to avoid some crash or failure but not fixing the
> actual problem
> 
> Erez, can you comment?
> 
> Or.