pull headers in qdisc_pkt_len_segs_init()

Summary

In the Linux kernel, the following vulnerability has been resolved: net: pull headers in qdisc_pkt_len_segs_init() Most ndo_start_xmit() methods expects headers of gso packets to be already in skb->head. net/core/tso.c users are particularly at risk, because tso_build_hdr() does a memcpy(hdr, skb->data, hdr_len); qdisc_pkt_len_segs_init() already does a dissection of gso packets. Use pskb_may_pull() instead of skb_header_pointer() to make sure drivers do not have to reimplement this. Some malicious packets could be fed, detect them so that we can drop them sooner with a new SKB_DROP_REASON_SKB_BAD_GSO drop_reason. A flaw was found in the Linux kernel's handling of Generic Segmentation Offload (GSO) packet headers. This vulnerability occurs when the `qdisc_pkt_len_segs_init()` function does not properly pull headers into the expected memory location, which can lead to incorrect processing by network drivers. A remote attacker could exploit this by sending specially crafted malicious packets, potentially causing a denial of service (DoS) or other unexpected system behavior. Red Hat severity: Important — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-131. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.