Re: [PATCH net-next v4 03/14] ibmveth: Refactor RX resource allocation for MQ RX bring-up

[Jakub Kicinski <kuba@kernel.org>]

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---
ibmveth: Refactor RX resource allocation for MQ RX bring-up

This moves the filter list and per-queue RX ring allocation out of
ibmveth_open() into four new helpers, and wires them into both the
open error unwind and ibmveth_close().  Runtime behaviour is meant to
stay single-queue since num_rx_queues is still 1.

> diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
> index 8e758362cb263..1007dd95cde02 100644
> --- a/drivers/net/ethernet/ibm/ibmveth.c
> +++ b/drivers/net/ethernet/ibm/ibmveth.c
> @@ -151,6 +151,184 @@ static unsigned int ibmveth_real_max_tx_queues(void)
>  	return min(n_cpu, IBMVETH_MAX_QUEUES);
>  }
>  
> +/**
> + * ibmveth_alloc_filter_list - Allocate and map filter list
> + * @adapter: ibmveth adapter structure
> + *
> + * Return: 0 on success, negative error code on failure
> + */
> +static int
> +ibmveth_alloc_filter_list(struct ibmveth_adapter *adapter)
> +{
> +	struct device *dev = &adapter->vdev->dev;
> +	struct net_device *netdev = adapter->netdev;
> +
> +	adapter->filter_list_addr = (void *)get_zeroed_page(GFP_KERNEL);
> +	if (!adapter->filter_list_addr) {
> +		netdev_err(netdev, "unable to allocate filter pages\n");
> +		return -ENOMEM;
> +	}
> +
> +	adapter->filter_list_dma = dma_map_single(dev,
> +						  adapter->filter_list_addr,
> +						  4096, DMA_BIDIRECTIONAL);
> +	if (dma_mapping_error(dev, adapter->filter_list_dma)) {
> +		netdev_err(netdev, "unable to map filter list pages\n");
> +		free_page((unsigned long)adapter->filter_list_addr);
> +		adapter->filter_list_addr = NULL;
> +		return -ENOMEM;
> +	}

[Severity: Medium]

Should this error path also clear adapter->filter_list_dma?  On failure
dma_map_single() has stored DMA_MAPPING_ERROR, which is ~(dma_addr_t)0 and
therefore non-zero, and only filter_list_addr is reset here.

The sibling helper added in the same patch does zero the cookie in the
same situation:

	if (dma_mapping_error(dev, adapter->buffer_list_dma[i])) {
		...
		adapter->buffer_list_dma[i] = 0;
		goto err_cleanup;
	}

so the two new helpers appear to disagree on the convention.

> +
> +	netdev_dbg(netdev, "filter list @ 0x%p (DMA: 0x%llx)\n",
> +		   adapter->filter_list_addr,
> +		   (unsigned long long)adapter->filter_list_dma);
> +
> +	return 0;
> +}
> +
> +/**
> + * ibmveth_free_filter_list - Free filter list resources
> + * @adapter: ibmveth adapter structure
> + */
> +static void
> +ibmveth_free_filter_list(struct ibmveth_adapter *adapter)
> +{
> +	struct device *dev = &adapter->vdev->dev;
> +
> +	if (adapter->filter_list_dma) {
> +		dma_unmap_single(dev, adapter->filter_list_dma, 4096,
> +				 DMA_BIDIRECTIONAL);
> +		adapter->filter_list_dma = 0;
> +	}

[Severity: Medium]

Can this unmap the DMA_MAPPING_ERROR sentinel?  ibmveth_free_filter_list()
treats any non-zero filter_list_dma as a live mapping, and the mapping-error
branch of ibmveth_alloc_filter_list() leaves the sentinel behind.

The state looks reachable without dev_close().  ibmveth_set_csum_offload(),
ibmveth_set_tso(), ibmveth_change_mtu() and veth_pool_store() all call
ibmveth_close() and then ibmveth_open() directly while netif_running() is
still true:

	if (netif_running(dev)) {
		restart = 1;
		ibmveth_close(dev);
	}
	...
	if (restart)
		rc2 = ibmveth_open(dev);

If that re-open fails at the dma_mapping_error() check in
ibmveth_alloc_filter_list(), open() returns through the out: label without
calling ibmveth_free_filter_list(), so the adapter is left with
filter_list_addr == NULL and filter_list_dma == DMA_MAPPING_ERROR while the
netdev is still marked running.  A later "ip link set dev ethX down" then
reaches ndo_stop == ibmveth_close() -> ibmveth_free_filter_list() and unmaps
that invalid address.

On pseries the dma_iommu path catches this in iommu_free_check(), which emits
a ratelimited "iommu_free: invalid entry" message and a WARN_ON(1) (a panic
with panic_on_warn set), so no TCE state is changed, but the backtrace is
still user triggerable with CAP_NET_ADMIN plus a mapping failure.

Setting adapter->filter_list_dma = 0 in that error branch, matching
ibmveth_alloc_rx_queues(), would make the guard here reliable.

This is still present unchanged at the end of the series (a3781f4ae789), so
a later patch does not appear to address it.

> +
> +	if (adapter->filter_list_addr) {
> +		free_page((unsigned long)adapter->filter_list_addr);
> +		adapter->filter_list_addr = NULL;
> +	}
> +}
> +

[ ... ]

> +		adapter->buffer_list_dma[i] =
> +			dma_map_single(dev, adapter->buffer_list_addr[i],
> +				       4096, DMA_BIDIRECTIONAL);
> +		if (dma_mapping_error(dev, adapter->buffer_list_dma[i])) {
> +			netdev_err(netdev,
> +				   "unable to map buffer list for queue %d\n",
> +				   i);
> +			adapter->buffer_list_dma[i] = 0;
> +			goto err_cleanup;
> +		}
> +

[ ... ]

> @@ -627,74 +805,34 @@ static int ibmveth_open(struct net_device *netdev)
>  
> -	rc = -ENOMEM;
> -	adapter->buffer_list_addr[0] = (void *)get_zeroed_page(GFP_KERNEL);
> -	if (!adapter->buffer_list_addr[0]) {
> -		netdev_err(netdev, "unable to allocate list pages\n");
> +	rc = ibmveth_alloc_filter_list(adapter);
> +	if (rc)
>  		goto out;
> -	}

[ ... ]

> @@ -753,26 +889,12 @@ static int ibmveth_open(struct net_device *netdev)
> +	ibmveth_cleanup_rx_resources(adapter);
>  out_free_filter_list:
> -	free_page((unsigned long)adapter->filter_list_addr);
> -out_free_buffer_list:
> -	free_page((unsigned long)adapter->buffer_list_addr[0]);
> +	ibmveth_free_filter_list(adapter);
>  out:
>  	napi_disable(&adapter->napi[0]);
>  	return rc;

[ ... ]