netdev - Re: [PATCH net 0/2] intel: Interpret .set

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] [day] [month] [year] [list]

Message-ID: <61d1e671-820d-4afd-ae90-887d302f1be2@intel.com>
Date: Thu, 16 May 2024 10:21:06 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Larysa Zaremba <larysa.zaremba@...el.com>, netdev <netdev@...r.kernel.org>
CC: Jakub Kicinski <kuba@...nel.org>, David Miller <davem@...emloft.net>,
	Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>, Chandan Kumar Rout
	<chandanx.rout@...el.com>, Pucha Himasekhar Reddy
	<himasekharx.reddy.pucha@...el.com>, Maciej Fijalkowski
	<maciej.fijalkowski@...el.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>, Igor Bagnucki <igor.bagnucki@...el.com>,
	Krishneil Singh <krishneil.k.singh@...el.com>, Simon Horman
	<horms@...nel.org>
Subject: Re: [PATCH net 0/2] intel: Interpret .set_channels() input
 differently



On 5/16/2024 1:44 AM, Larysa Zaremba wrote:
> On Tue, May 14, 2024 at 11:51:11AM -0700, Jacob Keller wrote:
>> The ice and idpf drivers can trigger a crash with AF_XDP due to incorrect
>> interpretation of the asymmetric Tx and Rx parameters in their
>> .set_channels() implementations:
>>
>> 1. ethtool -l <IFNAME> -> combined: 40
>> 2. Attach AF_XDP to queue 30
>> 3. ethtool -L <IFNAME> rx 15 tx 15
>>    combined number is not specified, so command becomes {rx_count = 15,
>>    tx_count = 15, combined_count = 40}.
>> 4. ethnl_set_channels checks, if there are any AF_XDP of queues from the
>>    new (combined_count + rx_count) to the old one, so from 55 to 40, check
>>    does not trigger.
>> 5. the driver interprets `rx 15 tx 15` as 15 combined channels and deletes
>>    the queue that AF_XDP is attached to.
>>
>> This is fundamentally a problem with interpreting a request for asymmetric
>> queues as symmetric combined queues.
>>
>> Fix the ice and idpf drivers to stop interpreting such requests as a
>> request for combined queues. Due to current driver design for both ice and
>> idpf, it is not possible to support requests of the same count of Tx and Rx
>> queues with independent interrupts, (i.e. ethtool -L <IFNAME> rx 15 tx 15)
>> so such requests are now rejected.
>>
>> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
>> ---
> 
> Please, do not merge, first patch contains a redundant check
> 
> if (!ch->combined_count)
> 
> I will send another version.

I looked at the ethnl_set_channels and was at first confused because
there is no explicit check for just !ch->combined_count. That makes
sense since it was previously possible to just set both tx and rx which
we were incorrectly interpreting as combined channels.

The core code *does* check that we have at least one Tx and one Rx
channel by checking the following conditions:

>         /* ensure there is at least one RX and one TX channel */
>         if (!channels.combined_count && !channels.rx_count)
>                 err_attr = ETHTOOL_A_CHANNELS_RX_COUNT;
>         else if (!channels.combined_count && !channels.tx_count)
>                 err_attr = ETHTOOL_A_CHANNELS_TX_COUNT;
>         else
>                 err_attr = 0;


This combined with our added check in the driver that we can't have both
ch->rx_count and ch->tx_count set, this effectively covers the same test
that ch->combined_count covers, so its unnecessary to waste time
checking it again.

Makes sense.

Thanks,
Jake