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[86.7.189.148]) by smtp.gmail.com with ESMTPSA id v4sm192184wme.14.2021.04.29.07.22.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Apr 2021 07:22:07 -0700 (PDT) Subject: Re: [PATCH] sfc: adjust efx->xdp_tx_queue_count with the real number of initialized queues To: Ignat Korchagin , habetsm.xilinx@gmail.com, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org Cc: kernel-team@cloudflare.com, stable@vger.kernel.org References: <20210427210938.661700-1-ignat@cloudflare.com> From: Edward Cree Message-ID: Date: Thu, 29 Apr 2021 15:22:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20210427210938.661700-1-ignat@cloudflare.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 27/04/2021 22:09, Ignat Korchagin wrote: > efx->xdp_tx_queue_count is initially initialized to num_possible_cpus() and is > later used to allocate and traverse efx->xdp_tx_queues lookup array. However, > we may end up not initializing all the array slots with real queues during > probing. This results, for example, in a NULL pointer dereference, when running > "# ethtool -S ", similar to below ... > diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c > index 1bfeee283ea9..a3ca406a3561 100644 > --- a/drivers/net/ethernet/sfc/efx_channels.c > +++ b/drivers/net/ethernet/sfc/efx_channels.c > @@ -914,6 +914,8 @@ int efx_set_channels(struct efx_nic *efx) > } > } > } > + if (xdp_queue_number) Wait, why is this guard condition needed? What happens if we had nonzero efx->xdp_tx_queue_count initially, but we end up with no TXQs available for XDP at all (so xdp_queue_number == 0)? -ed > + efx->xdp_tx_queue_count = xdp_queue_number; > > rc = netif_set_real_num_tx_queues(efx->net_dev, efx->n_tx_channels); > if (rc) >