CVE-2024-41066

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

ibmvnic: Add tx check to prevent skb leak

Below is a summary of how the driver stores a reference to an skb during transmit: tx_buff[free_map[consumer_index]]->skb = new_skb; free_map[consumer_index] = IBMVNIC_INVALID_MAP; consumer_index ++; Where variable data looks like this: free_map == [4, IBMVNIC_INVALID_MAP, IBMVNIC_INVALID_MAP, 0, 3] consumer_index^ tx_buff == [skb=null, skb=<ptr>, skb=<ptr>, skb=null, skb=null]

The driver has checks to ensure that free_map[consumer_index] pointed to a valid index but there was no check to ensure that this index pointed to an unused/null skb address. So, if, by some chance, our free_map and tx_buff lists become out of sync then we were previously risking an skb memory leak. This could then cause tcp congestion control to stop sending packets, eventually leading to ETIMEDOUT.

Therefore, add a conditional to ensure that the skb address is null. If not then warn the user (because this is still a bug that should be patched) and free the old pointer to prevent memleak/tcp problems.

This vulnerability exists in the driver for IBM System i/p virtual network adapters. By exploiting this vulnerability, an attacker can cause a leak in memory pools used for processing network traffic, which can cause the kernel's congestion control mechanisms to erroneously stop transmitting packets, effectively a denial of service. Because the affected hardware is uncommon, and because an attacker must be able to generate a large amount of network traffic that is handled specifically by a virtual NIC on that hardware, Red Hat assesses the impact of this vulnerability as Low.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, prevent module ibmvnic from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.