CVE-2024-49979

/// Technical description

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

net: gso: fix tcp fraglist segmentation after pull from frag_list

Detect tcp gso fraglist skbs with corrupted geometry (see below) and

pass these to skb_segment instead of skb_segment_list, as the first

can segment them correctly.

Valid SKB_GSO_FRAGLIST skbs

- consist of two or more segments

- the head_skb holds the protocol headers plus first gso_size

- one or more frag_list skbs hold exactly one segment

- all but the last must be gso_size

Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can

modify these skbs, breaking these invariants.

In extreme cases they pull all data into skb linear. For TCP, this

causes a NULL ptr deref in __tcpv4_gso_segment_list_csum at

tcp_hdr(seg->next).

Detect invalid geometry due to pull, by checking head_skb size.

Don't just drop, as this may blackhole a destination. Convert to be

able to pass to regular skb_segment.

Approach and description based on a patch by Wille

/// 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