veth: fix skb length accounting after XDP frag adjustment

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74612
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 16:16:33 UTC
Updated2026-08-23 13:16:46 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: veth: fix skb length accounting after XDP frag adjustment veth exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, veth_xdp_rcv_skb() copies xdp_frags_size back to skb->data_len but leaves skb->len containing the old fragment contribution. After a fragment shrink, this makes skb_headlen() larger than the actual linear area. In the reproduced UDP receive path, __skb_datagram_iter() copied 1024 bytes past the actual linear tail to userspace, starting at struct skb_shared_info. The copied bytes included the affected skb's nr_frags, xdp_frags_size, and a kernel pointer from skb_shinfo(skb)->frags[0]. Real packet data was displaced by the same amount and truncated at the end. Subtract the old data_len before replacing it and add the new data_len afterwards, keeping skb->len and skb->data_len synchronized. Additionally, bpf_xdp_pull_data() can advance data_end while leaving frags present. The skb is then still non-linear, so the old __skb_put(skb, off) triggers SKB_LINEAR_ASSERT(). Use skb_set_tail_pointer() and update skb->len explicitly instead, following bpf_prog_run_generic_xdp(). Unlike __skb_put(), skb_set_tail_pointer() does not require a linear skb. A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by 1024 bytes from its fragment area. Before the fix, all 10 runs produced corrupted payloads. After the fix, all 10 runs matched the expected payload exactly. A forced-tailroom reproducer also exercises bpf_xdp_pull_data() with frags still present; the old code triggers SKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 718a18a0c8a67f97781e40bdef7cdd055c430996 0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5 git Not specified
CNA Linux Linux affected 718a18a0c8a67f97781e40bdef7cdd055c430996 2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139 git Not specified
CNA Linux Linux affected 718a18a0c8a67f97781e40bdef7cdd055c430996 41b96667d42b74bb4b137f1bb78b611a953c5943 git Not specified
CNA Linux Linux affected 718a18a0c8a67f97781e40bdef7cdd055c430996 cdf745b7a777f87f51666e5d8f4c6fc279bcf54d git Not specified
CNA Linux Linux affected 718a18a0c8a67f97781e40bdef7cdd055c430996 3205b0652a37255dbb7ca8f3d942c8d8aa677c21 git Not specified
CNA Linux Linux affected 718a18a0c8a67f97781e40bdef7cdd055c430996 cb6379feaaff11c4e1e79c26c745ffa23182768a git Not specified
CNA Linux Linux affected 5.18 Not specified
CNA Linux Linux unaffected 5.18 semver Not specified
CNA Linux Linux unaffected 6.1.184 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.152 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.104 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/cdf745b7a777f87f51666e5d8f4c6fc279bcf54d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cb6379feaaff11c4e1e79c26c745ffa23182768a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/41b96667d42b74bb4b137f1bb78b611a953c5943 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3205b0652a37255dbb7ca8f3d942c8d8aa677c21 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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