tunnels: fix kasan splat when generating ipv4 pmtu error

Summary

In the Linux kernel, the following vulnerability has been resolved: tunnels: fix kasan splat when generating ipv4 pmtu error If we try to emit an icmp error in response to a nonliner skb, we get BUG: KASAN: slab-out-of-bounds in ip_compute_csum+0x134/0x220 Read of size 4 at addr ffff88811c50db00 by task iperf3/1691 CPU: 2 PID: 1691 Comm: iperf3 Not tainted 6.5.0-rc3+ #309 [..] kasan_report+0x105/0x140 ip_compute_csum+0x134/0x220 iptunnel_pmtud_build_icmp+0x554/0x1020 skb_tunnel_check_pmtu+0x513/0xb80 vxlan_xmit_one+0x139e/0x2ef0 vxlan_xmit+0x1867/0x2760 dev_hard_start_xmit+0x1ee/0x4f0 br_dev_queue_push_xmit+0x4d1/0x660 [..] ip_compute_csum() cannot deal with nonlinear skbs, so avoid it. After this change, splat is gone and iperf3 is no longer stuck.

Timeline

1. Oct 4, 2025, 3:44 PM UTCCVE published
2. Oct 15, 2026, 9:35 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 15, 2026, 9:41 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 5850c391fd7e25662334cb3cbf29a62bcbff1084; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in e95808121953410db8c59f0abfde70ac0d34222c; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in da5f42a6e7485fbb7a6dbd6a2b3045e19e4df5cc; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in fe6a9f7516735be9fdabab00e47ef7a3403a174d; From 4cb47a8644cc9eb8ec81190a50e79e6530d0297f · fixed in 6a7ac3d20593865209dceb554d8b3f094c6bd940

• Linux Linux

  5.9

• KernelLinux

  From 5.9.0 · fixed in 5.10.191; From 5.11.0 · fixed in 5.15.127; From 5.16.0 · fixed in 6.1.46; From 6.2.0 · fixed in 6.4.11

References 5