netdev - RE: [PATCH V1 net 04/11] net: ena: fix incorrect default RSS key

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Date:   Mon, 3 Feb 2020 13:59:35 +0000
From:   "Jubran, Samih" <sameehj@...zon.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        "Machulsky, Zorik" <zorik@...zon.com>,
        "Matushevsky, Alexander" <matua@...zon.com>,
        "Bshara, Saeed" <saeedb@...zon.com>,
        "Wilson, Matt" <msw@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        "Bshara, Nafea" <nafea@...zon.com>,
        "Tzalik, Guy" <gtzalik@...zon.com>,
        "Belgazal, Netanel" <netanel@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "Herrenschmidt, Benjamin" <benh@...zon.com>,
        "Dagan, Noam" <ndagan@...zon.com>
Subject: RE: [PATCH V1 net 04/11] net: ena: fix incorrect default RSS key



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Wednesday, January 29, 2020 6:03 PM
> To: Jubran, Samih <sameehj@...zon.com>
> Cc: davem@...emloft.net; netdev@...r.kernel.org; Kiyanovski, Arthur
> <akiyano@...zon.com>; Woodhouse, David <dwmw@...zon.co.uk>;
> Machulsky, Zorik <zorik@...zon.com>; Matushevsky, Alexander
> <matua@...zon.com>; Bshara, Saeed <saeedb@...zon.com>; Wilson,
> Matt <msw@...zon.com>; Liguori, Anthony <aliguori@...zon.com>;
> Bshara, Nafea <nafea@...zon.com>; Tzalik, Guy <gtzalik@...zon.com>;
> Belgazal, Netanel <netanel@...zon.com>; Saidi, Ali
> <alisaidi@...zon.com>; Herrenschmidt, Benjamin <benh@...zon.com>;
> Dagan, Noam <ndagan@...zon.com>
> Subject: Re: [PATCH V1 net 04/11] net: ena: fix incorrect default RSS key
> 
> On Wed, 29 Jan 2020 14:04:15 +0000, Sameeh Jubran wrote:
> > From: Arthur Kiyanovski <akiyano@...zon.com>
> >
> > Bug description:
> > When running "ethtool -x <if_name>" the key shows up as all zeros.
> >
> > When we use "ethtool -X <if_name> hfunc toeplitz hkey
> > <some:random:key>" to set the key and then try to retrieve it using
> > "ethtool -x <if_name>" then we return the correct key because we return
> the one we saved.
> >
> > Bug cause:
> > We don't fetch the key from the device but instead return the key that
> > we have saved internally which is by default set to zero upon
> > allocation.
> >
> > Fix:
> > This commit fixes the issue by initializing the key to the default key
> > that is used by the device.
> >
> > Fixes: 1738cd3ed342 ("net: ena: Add a driver for Amazon Elastic
> > Network Adapters (ENA)")
> > Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
> > Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
> 
> So is the device actually using that key by default?
> 
> Hard coding a default RSS key makes it trivial for DDoS attackers to target
> specific queues, doesn't it?
> 
> Please follow the best practice of initializing your key with
> netdev_rss_key_fill() and configuring the device with it at startup.
> 
> > diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c
> > b/drivers/net/ethernet/amazon/ena/ena_com.c
> > index e54c44fdc..769339043 100644
> > --- a/drivers/net/ethernet/amazon/ena/ena_com.c
> > +++ b/drivers/net/ethernet/amazon/ena/ena_com.c
> > @@ -64,6 +64,15 @@
> >
> >  #define ENA_POLL_MS	5
> >
> > +/* Default Microsoft RSS key, used for HRSS. */ static const u8
> > +rss_hash_key[ENA_HASH_KEY_SIZE] = {
> > +		0x6d, 0x5a, 0x56, 0xda, 0x25, 0x5b, 0x0e, 0xc2,
> > +		0x41, 0x67, 0x25, 0x3d, 0x43, 0xa3, 0x8f, 0xb0,
> > +		0xd0, 0xca, 0x2b, 0xcb, 0xae, 0x7b, 0x30, 0xb4,
> > +		0x77, 0xcb, 0x2d, 0xa3, 0x80, 0x30, 0xf2, 0x0c,
> > +		0x6a, 0x42, 0xb7, 0x3b, 0xbe, 0xac, 0x01, 0xfa
> 
> You also have an extra tab here for no reason.
> 
> > +};
> > +
> >
> >
> /**********************************************************
> ***********
> > ********/
> >
> /**********************************************************
> ***********
> > ********/
> >
> /**********************************************************
> ***********
> > ********/

Hi Jakub,

Thanks for your comments,
Will fix ASAP and send v2.