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

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Date:   Wed, 26 Apr 2017 20:52:30 +0800
From:   Honggang LI <honli@...hat.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Or Gerlitz <gerlitz.or@...il.com>,
        Doug Ledford <dledford@...hat.com>,
        Erez Shitrit <erezsh@....mellanox.co.il>,
        Erez Shitrit <erezsh@...lanox.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH] IB/IPoIB: Check the headroom size

On Wed, Apr 26, 2017 at 09:46:34AM +0200, Paolo Abeni wrote:
> On Wed, 2017-04-26 at 00:50 +0300, Or Gerlitz wrote:
> > so maybe @ least for the time being, we should be picking Hong's patch
> > with proper change log and without the giant stack dump till we have
> > something better. If you agree, can you do the re-write of the change
> > log?
> 
> I think that Hong's patch is following the correct way to fix the
> issue: ipoib_hard_header() can't assume that the skb headroom is at
> least IPOIB_HARD_LEN bytes, as wrongly implied by commit fc791b633515
> (my fault, I'm sorry).
> 
> Perhaps we can make the code a little more robust with something
> alongside the following (only compile tested):
> ---
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> index d1d3fb7..d53d2e1 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> @@ -1160,6 +1160,11 @@ static int ipoib_hard_header(struct sk_buff *skb,
>                              const void *daddr, const void *saddr, unsigned len)
>  {
>         struct ipoib_header *header;
> +       int ret;
> +
> +       ret = skb_cow_head(skb, IPOIB_HARD_LEN);

I don't think so. When this skb_under_panic arise, all slaves had been
removed from a busy bonding interface, so it is better to immediately
give up and return error.

> +       if (ret)
> +               return ret;
>  
>         header = (struct ipoib_header *) skb_push(skb, sizeof *header);
> ---
> 
> Paolo
> --
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