netdev - Re: [PATCH V1 net] net: ena: don't wake up tx queue when down

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Date:   Mon, 16 Sep 2019 21:40:53 +0200 (CEST)
From:   David Miller <davem@...emloft.net>
To:     sameehj@...zon.com
Cc:     netdev@...r.kernel.org, dwmw@...zon.com, zorik@...zon.com,
        matua@...zon.com, saeedb@...zon.com, msw@...zon.com,
        aliguori@...zon.com, nafea@...zon.com, gtzalik@...zon.com,
        netanel@...zon.com, alisaidi@...zon.com, benh@...zon.com,
        akiyano@...zon.com
Subject: Re: [PATCH V1 net] net: ena: don't wake up tx queue when down

From: <sameehj@...zon.com>
Date: Sun, 15 Sep 2019 17:29:44 +0300

> From: Sameeh Jubran <sameehj@...zon.com>
> 
> There is a race condition that can occur when calling ena_down().
> The ena_clean_tx_irq() - which is a part of the napi handler -
> function might wake up the tx queue when the queue is supposed
> to be down (during recovery or changing the size of the queues
> for example) This causes the ena_start_xmit() function to trigger
> and possibly try to access the destroyed queues.
> 
> The race is illustrated below:
> 
> Flow A:                                       Flow B(napi handler)
> ena_down()
>    netif_carrier_off()
>    netif_tx_disable()
>                                                       ena_clean_tx_irq()
>                                                          netif_tx_wake_queue()
>    ena_napi_disable_all()
>    ena_destroy_all_io_queues()
> 
> After these flows the tx queue is active and ena_start_xmit() accesses
> the destroyed queue which leads to a kernel panic.
> 
> fixes: 1738cd3ed342 (net: ena: Add a driver for Amazon Elastic Network Adapters (ENA))
> 
> Signed-off-by: Sameeh Jubran <sameehj@...zon.com>

Applied.