fou: Fix use-after-free in fou_create()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74496
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 13:17:54 UTC
Updated2026-08-15 13:17:54 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: fou: Fix use-after-free in fou_create() fou_create() publishes struct fou through sk_user_data before adding the new FOU port to the per-netns list. If fou_add_to_port_list() fails, the error path frees fou while it is still reachable through sk_user_data. A concurrent receive can then dereference the freed object in fou_from_sock(). This ordering issue was previously noted in the linked discussion. The failure is reachable when local port 0 is requested. Each socket binds to a different ephemeral port, but fou_cfg_cmp() compares the requested port 0 and reports -EALREADY once an entry already exists. Release the tunnel socket before freeing fou so sk_user_data is cleared first, and defer reclamation with kfree_rcu() to protect concurrent RCU readers. This matches the lifetime handling in fou_release().

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 a28d8903bfe76089ea4bbdbff9976965f9ef8107 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 b14361aca6350ff7907b0e9903c7b94dc7d5d4a0 git Not specified
CNA Linux Linux affected 3.18 Not specified
CNA Linux Linux unaffected 3.18 semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc6 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a28d8903bfe76089ea4bbdbff9976965f9ef8107 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b14361aca6350ff7907b0e9903c7b94dc7d5d4a0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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