netdev - Re: kernel panic with time-stamping in phy devices (monitor mode)

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Date:	Mon, 6 Dec 2010 08:01:23 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Andrew Watts <akwatts@...il.com>,
	Richard Cochran <richardcochran@...il.com>,
	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	stable@...nel.org
Subject: Re: kernel panic with time-stamping in phy devices (monitor mode)

On Sun, Dec 5, 2010 at 8:24 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le samedi 04 décembre 2010 à 12:46 -0800, Andrew Watts a écrit :
>
>> Eric, I echo the thanks on the lightning patch.
>> Impressive turnaround!
>>
>> There's an open bug report on the kernel's bugzilla
>> for 2.6.36 (#24102). What is the best way to tie these
>> together?
>
> Thanks Andy, here is the official patch submission I am going to make.
>
> [PATCH net-2.6] net: fix skb_defer_rx_timestamp()
>
> After commit c1f19b51d1d8 (net: support time stamping in phy devices.),
> kernel might crash if CONFIG_NETWORK_PHY_TIMESTAMPING=y and
> skb_defer_rx_timestamp() handles a packet without an ethernet header.
>
> Fixes kernel bugzilla #24102
>
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=24102
> Reported-and-tested-by: Andrew Watts <akwatts@...il.com>
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Richard Cochran <richardcochran@...il.com>
> Cc: stable@...nel.org
> ---
>  net/core/timestamping.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/timestamping.c b/net/core/timestamping.c
> index 0ae6c22..c4fbf85 100644
> --- a/net/core/timestamping.c
> +++ b/net/core/timestamping.c
> @@ -96,11 +96,13 @@ bool skb_defer_rx_timestamp(struct sk_buff *skb)
>        struct phy_device *phydev;
>        unsigned int type;
>
> -       skb_push(skb, ETH_HLEN);
> +       if (skb->data - ETH_HLEN < skb->head)
> +               return false;

How about using skb_headroom(skb) < ETH_HLEN ?

And I checked the code of skb_push(). If the headroom of a skb is less
than the requested, Linux will panic with a message titled
"skb_under_panic()". But I can't find this info in the Oops. Maybe the
Oops isn't complete.


-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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