Re: [PATCH] sfc: adjust efx->xdp_tx_queue_count with the real number of initialized queues
From: Edward Cree <ecree.xilinx@gmail.com>
Date: 2021-04-29 14:22:13
Also in:
stable
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 <iface>", similar to below
...
quoted hunk ↗ jump to hunk
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)