CVE-2024-49979 – Linux Kernel TCP GSO Fraglist Null Pointer Dereference Vulnerability

CVE ID : CVE-2024-49979

Published : Oct. 21, 2024, 6:15 p.m. | 1 hour, 3 minutes ago

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 Willem de Bruijn.

Severity: 0.0 | NA

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CVE-2024-49979 – Linux Kernel TCP GSO Fraglist Null Pointer Dereference Vulnerability