CVE-2021-47399

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ixgbe: Fix NULL pointer dereference in ixgbe_xdp_setup

The ixgbe driver currently generates a NULL pointer dereference with

some machine (online cpus < 63). This is due to the fact that the

maximum value of num_xdp_queues is nr_cpu_ids. Code is in

"ixgbe_set_rss_queues"".

Here's how the problem repeats itself:

Some machine (online cpus < 63), And user set num_queues to 63 through

ethtool. Code is in the "ixgbe_set_channels",

adapter->ring_feature[RING_F_FDIR].limit = count;

It becomes 63.

When user use xdp, "ixgbe_set_rss_queues" will set queues num.

adapter->num_rx_queues = rss_i;

adapter->num_tx_queues = rss_i;

adapter->num_xdp_queues = ixgbe_xdp_queues(adapter);

And rss_i's value is from

f = &adapter->ring_feature[RING_F_FDIR];

rss_i = f->indices = f->limit;

So "num_rx_queues" > "num_xdp_queues", when run to "ixgbe_xdp_setup",

for (i = 0; i < adapter->num_rx_queues; i++)

if (adapter->xdp_ring[i]->xsk

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References