netdev - Re: [PATCH] IB/IPoIB: Check the headroom size

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Date:   Tue, 25 Apr 2017 13:32:59 +0300
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Honggang LI <honli@...hat.com>, Erez Shitrit <erezsh@...lanox.com>
Cc:     Doug Ledford <dledford@...hat.com>,
        "Hefty, Sean" <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] IB/IPoIB: Check the headroom size

On Tue, Apr 25, 2017 at 12:55 PM, Honggang LI <honli@...hat.com> wrote:
> From: Honggang Li <honli@...hat.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.

> 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.