{"id":"CVE-2026-43392","state":"PUBLISHED","title":"sched_ext: Fix starvation of scx_enable() under fair-class saturation","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix starvation of scx_enable() under fair-class saturation\n\nDuring scx_enable(), the READY -> ENABLED task switching loop changes the\ncalling thread's sched_class from fair to ext. Since fair has higher\npriority than ext, saturating fair-class workloads can indefinitely starve\nthe enable thread, hanging the system. This was introduced when the enable\npath switched from preempt_disable() to scx_bypass() which doesn't protect\nagainst fair-class starvation. Note that the original preempt_disable()\nprotection wasn't complete either - in partial switch modes, the calling\nthread could still be starved after preempt_enable() as it may have been\nswitched to ext class.\n\nFix it by offloading the enable body to a dedicated system-wide RT\n(SCHED_FIFO) kthread which cannot be starved by either fair or ext class\ntasks. scx_enable() lazily creates the kthread on first use and passes the\nops pointer through a struct scx_enable_cmd containing the kthread_work,\nthen synchronously waits for completion.\n\nThe workfn runs on a different kthread from sch->helper (which runs\ndisable_work), so it can safely flush disable_work on the error path\nwithout deadlock.","publishedAt":"2026-05-08T14:21:36.692Z","updatedAt":"2026-05-11T22:23:41.885Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b","versionType":"git"},{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"c44198f25fdfecc0ec0fe366bf8a47fe17d8e229","versionType":"git"},{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81","versionType":"git"},{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"b06ccbabe2506fd70b9167a644978b049150224a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext.c"]}],"references":["https://git.kernel.org/stable/c/e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b","https://git.kernel.org/stable/c/c44198f25fdfecc0ec0fe366bf8a47fe17d8e229","https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81","https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43392.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43392","state":"PUBLISHED","datePublished":"2026-05-08T14:21:36.692Z","dateUpdated":"2026-05-11T22:23:41.885Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.007Z"},"containers":{"cna":{"title":"sched_ext: Fix starvation of scx_enable() under fair-class saturation","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix starvation of scx_enable() under fair-class saturation\n\nDuring scx_enable(), the READY -> ENABLED task switching loop changes the\ncalling thread's sched_class from fair to ext. Since fair has higher\npriority than ext, saturating fair-class workloads can indefinitely starve\nthe enable thread, hanging the system. This was introduced when the enable\npath switched from preempt_disable() to scx_bypass() which doesn't protect\nagainst fair-class starvation. Note that the original preempt_disable()\nprotection wasn't complete either - in partial switch modes, the calling\nthread could still be starved after preempt_enable() as it may have been\nswitched to ext class.\n\nFix it by offloading the enable body to a dedicated system-wide RT\n(SCHED_FIFO) kthread which cannot be starved by either fair or ext class\ntasks. scx_enable() lazily creates the kthread on first use and passes the\nops pointer through a struct scx_enable_cmd containing the kthread_work,\nthen synchronously waits for completion.\n\nThe workfn runs on a different kthread from sch->helper (which runs\ndisable_work), so it can safely flush disable_work on the error path\nwithout deadlock."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b","versionType":"git"},{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"c44198f25fdfecc0ec0fe366bf8a47fe17d8e229","versionType":"git"},{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81","versionType":"git"},{"version":"8c2090c504e998c8f34ec870bae71dafcc96a6e0","status":"affected","lessThan":"b06ccbabe2506fd70b9167a644978b049150224a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b"},{"url":"https://git.kernel.org/stable/c/c44198f25fdfecc0ec0fe366bf8a47fe17d8e229"},{"url":"https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81"},{"url":"https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:23:41.885Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.18.20"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.19.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}