CVE-2026-68296
net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM
In the Linux kernel, the following vulnerability has been resolved: net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM Before commit 00d066a4d4ed ("netdev_features: convert NETIF_F_LLTX to dev->lltx"), NETIF_F_LLTX was set unconditionally in both __gre_tunnel_init() and ip6gre_tnl_init_features() alongside GRE_FEATURES: dev->features |= GRE_FEATURES | NETIF_F_LLTX; When that commit converted NETIF_F_LLTX to the dev->lltx flag, it placed 'dev->lltx = true' after the SEQ/CSUM early returns instead of before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or CSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition around their ndo_start_xmit. Since GRE xmit re-enters the stack via ip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the underlay device. CPU0 CPU1 ---- ---- lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); Fix by moving dev->lltx = true before the early returns in both functions, restoring the original unconditional behavior.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| Linux Linux |
≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383; < 9f948e9aede9678f4103457daf2bc9dd54c65a06 (affected, git) ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383; < 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3 (affected, git) ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383; < 2bffe379023512d280337c70faeb6a8cc435db5e (affected, git) ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383; < 675ed582c1aa4d919dd535490de08c015005c653 (affected, git) Other versions: unaffected |
CNA: Linux |
| Linux Linux |
6.12 (affected) ≥ 0; < 6.12 (unaffected, semver) ≥ 6.12.101; ≤ 6.12.* (unaffected, semver) ≥ 6.18.42; ≤ 6.18.* (unaffected, semver) ≥ 7.1.6; ≤ 7.1.* (unaffected, semver) ≥ 7.2; ≤ * (unaffected, original_commit_for_fix) Other versions: affected |
CNA: Linux |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
No CVSS assessment reported. An unscored record is not a low-severity determination.
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://git.kernel.org/stable/c/9f948e9aede9678f4103457daf2bc9dd54c65a06CNA: Linux
- https://git.kernel.org/stable/c/15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3CNA: Linux
- https://git.kernel.org/stable/c/2bffe379023512d280337c70faeb6a8cc435db5eCNA: Linux
- https://git.kernel.org/stable/c/675ed582c1aa4d919dd535490de08c015005c653CNA: Linux
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