net/sched: cls_route: fix fastmap use-after-free on filter

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74583
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-21 17:16:44 UTC
Updated2026-08-21 17:16:44 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: cls_route: fix fastmap use-after-free on filter The route4 classifier maintains a 16-slot fastmap cache that stores raw struct route4_filter pointers indexed by (id, iif). The reader (route4_classify) populates this cache via route4_set_fastmap() for every classified packet that hits a filter. The writer (route4_delete, route4_change) clears the cache via route4_reset_fastmap() before RCU-deferred kfree of the filter. This creates a UAF race: 1. Reader walks the RCU-protected bucket chain, finds filter f 2. Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work() 3. Reader calls route4_set_fastmap() and writes f into the cache *after* the writer's reset, caching a pointer about to be freed 4. After the RCU grace period, kfree(f) executes 5. Next classified packet on the same (id, iif) tuple hits the stale fastmap entry and reads f->res from freed memory Reproduced with an mdelay(100) accelerator in route4_set_fastmap() and a concurrent add/delete stress test (provided by both zdi and Santosh). Both triggered KASAN slab-use-after-free reports in the route4 fastmap paths. Fix: Introduce a per-filter boolean dying flag to suppress stale fastmap republishing by in-flight readers.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 7897198b26445b4009a057bda1986b94a99e5d5f git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 820f083c294ad6d319c02a7d43294f2ed2565139 git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 5ec9001be6d0eb527251125632ec8fe88278897f git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 b969984b2bdc85d721ce4047cd270cd37ec705a2 git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 a17f636c9330eac879822ce29f998e5abd1b72c1 git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 0e7a8cf8895b06d07c7311f028eba16ad742b9bc git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 ae9aff87025219005a2d16b4fe83d6f24643e50d git Not specified
CNA Linux Linux affected 1109c00547fc66df45b9ff923544be4c1e1bec13 47d7f7051253bdc02b1d245d87e38f16d31a74df git Not specified
CNA Linux Linux affected 3.18 Not specified
CNA Linux Linux unaffected 3.18 semver Not specified
CNA Linux Linux unaffected 5.10.265 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.216 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.183 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.152 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.104 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7897198b26445b4009a057bda1986b94a99e5d5f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0e7a8cf8895b06d07c7311f028eba16ad742b9bc 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b969984b2bdc85d721ce4047cd270cd37ec705a2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/47d7f7051253bdc02b1d245d87e38f16d31a74df 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/820f083c294ad6d319c02a7d43294f2ed2565139 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ae9aff87025219005a2d16b4fe83d6f24643e50d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5ec9001be6d0eb527251125632ec8fe88278897f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a17f636c9330eac879822ce29f998e5abd1b72c1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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