netdev - Re: [PATCH net 3/5] igb: fix race accessing page->

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 9 Oct 2014 22:54:56 -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 3/5] igb: fix race 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, 2) 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.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Change the title to :ixgbe: ...", then you have my ACK.
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>

Since this is apart of a series, if the changes to skbuff are ok, then
the changes to the Intel drivers are ok.

> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index d677b5a23b58..fec5212d4337 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -1865,12 +1865,10 @@ static bool ixgbe_add_rx_frag(struct ixgbe_ring *rx_ring,
>         /* flip page offset to other buffer */
>         rx_buffer->page_offset ^= truesize;
>
> -       /*
> -        * since we are the only owner of the page and we need to
> -        * increment it, just set the value to 2 in order to avoid
> -        * an unecessary locked operation
> +       /* Even if we own the page, we are not allowed to use atomic_set()
> +        * This would break get_page_unless_zero() users.
>          */
> -       atomic_set(&page->_count, 2);
> +       atomic_inc(&page->_count);
>  #else
>         /* move offset up to the next cache line */
>         rx_buffer->page_offset += truesize;
> --
> 2.1.0.rc2.206.gedb03e5
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Cheers,
Jeff
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html