CVE-2024-49979 Information

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.

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Reference

https://git.kernel.org/stable/c/3fdd8c83e83fa5e82f1b5585245c51e0355c9f46 https://git.kernel.org/stable/c/2d4a83a44428de45bfe9dccb0192a3711d1097e0 https://git.kernel.org/stable/c/17bd3bd82f9f79f3feba15476c2b2c95a9b11ff8

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

5.5