net/sched: act_skbmod: fix length calculations and avoid invalid header warnings

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-90078
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:16:57 UTC
Updated2026-09-17 17:16:57 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbmod: fix length calculations and avoid invalid header warnings syzbot reported a warning in skb_network_header_len() triggered by tcf_skbmod_act(): !skb_transport_header_was_set(skb) WARNING: CPU: 0 PID: 14949 at include/linux/skbuff.h:3243 skb_network_header_len include/linux/skbuff.h:3243 [inline] WARNING: CPU: 0 PID: 14949 at net/sched/act_skbmod.c:55 tcf_skbmod_act+0xfe8/0x1810 net/sched/act_skbmod.c:55 There are a few issues in tcf_skbmod_act(): 1. Calling skb_network_header_len() assumes skb->transport_header is set, which is not guaranteed when tcf_skbmod_act() runs at TC ingress. 2. Unconditionally calling skb_mac_header_len() at the beginning of tcf_skbmod_act() triggers a warning on L3 devices (e.g. TUN) where the MAC header is unset, evaluating to an underflowed garbage length. 3. On TC ingress, skb->data points to the network header. Adding the MAC header length to the IP header length causes skb_ensure_writable() to request more bytes than the actual IP packet length, dropping valid short packets (e.g. 28-byte UDP/IPv4 packets). Fix these by: - Using skb_network_offset(skb) + sizeof(struct iphdr/ipv6hdr) for SKBMOD_F_ECN so that the required length is correctly calculated on both ingress (offset == 0) and egress (offset == mac_len). - Setting max_edit_len to ETH_HLEN for Ethernet header modifications after validating ARPHRD_ETHER.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e 985a37781ade19061400100c2ba0f43979dd4d63 git Not specified
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e d896843d8d925f0adbba319020595cfb1a7bcd57 git Not specified
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e 0675cff3c2924eb9b80d9dd250cf56a1140af157 git Not specified
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e e8a2027b7e686784a69b2dfcee841d779919f313 git Not specified
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e 1719865b20b22c88d2a55e922eff5ca31b0841f6 git Not specified
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e 62126464f3a6159c0a3dd89e196ba65bfeb0afc6 git Not specified
CNA Linux Linux affected 56af5e749f20c3a540310c207dcc373f4f09156e 81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb git Not specified
CNA Linux Linux affected 5.15 Not specified
CNA Linux Linux unaffected 5.15 semver Not specified
CNA Linux Linux unaffected 5.15.221 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.188 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.110 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/e8a2027b7e686784a69b2dfcee841d779919f313 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/62126464f3a6159c0a3dd89e196ba65bfeb0afc6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d896843d8d925f0adbba319020595cfb1a7bcd57 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1719865b20b22c88d2a55e922eff5ca31b0841f6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0675cff3c2924eb9b80d9dd250cf56a1140af157 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/985a37781ade19061400100c2ba0f43979dd4d63 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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