net: ipv6: flowlabel: defer exclusive option free until RCU teardown

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Summary

CVECVE-2026-31680
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-25 09:16:01 UTC
Updated2026-04-25 09:16:01 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 4b6798024f7b2d535f3db1002c760143cdbd1bd3 git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 5a6b15f861b7c1304949e3350d23490a5fe429fd git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 8027964931785cb73d520ac70a342a3dc16c249b git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 414726b69921fe6355ae453f5b35e68dd078342a git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 572ce62778519a7d4d1c15f55dd2e45a474133c4 git Not specified
CNA Linux Linux affected d3aedd5ebd4b0b925b0bcda548066803e1318499 9ca562bb8e66978b53028fa32b1a190708e6a091 git Not specified
CNA Linux Linux affected 3.9 Not specified
CNA Linux Linux unaffected 3.9 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.134 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.81 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.22 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.12 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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