netdev - Re: [PATCH net 0/5] net: fix races accessing page->

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Date:	Thu, 9 Oct 2014 22:37:34 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Eric Dumazet <edumazet@...gle.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.h.duyck@...hat.com>,
	Andres Lagar-Cavilla <andreslc@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH net 0/5] net: fix races accessing page->_count

On Thu, Oct 9, 2014 at 10:24 PM, Eric Dumazet <edumazet@...gle.com> wrote:
> This is illegal to use atomic_set(&page->_count, ...) even if we 'own'
> the page. Other entities in the kernel need to use get_page_unless_zero()
> to get a reference to the page before testing page properties, so we could
> loose a refcount increment.
>
> The only case it is valid is when page->_count is 0, we can use this in
> __netdev_alloc_frag()
>
> Note that I never seen crashes caused by these races, the issue was reported
> by Andres Lagar-Cavilla and Hugh Dickins.
>
> Eric Dumazet (5):
>   fm10k: fix race accessing page->_count
>   igb: fix race accessing page->_count
>   igb: fix race accessing page->_count

Looks like the ixgbe patch has the incorrect title, or you patch igb twice. :-)

>   mlx4: fix race accessing page->_count
>   net: fix races in page->_count manipulation
>
>  drivers/net/ethernet/intel/fm10k/fm10k_main.c |  7 +++----
>  drivers/net/ethernet/intel/igb/igb_main.c     |  7 +++----
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |  8 +++-----
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c    |  6 +++---
>  net/core/skbuff.c                             | 25 ++++++++++++++++++-------
>  5 files changed, 30 insertions(+), 23 deletions(-)
>
> --
> 2.1.0.rc2.206.gedb03e5
>
> --
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-- 
Cheers,
Jeff
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