{"id":"CVE-2026-43392","summary":"sched_ext: Fix starvation of scx_enable() under fair-class saturation","details":"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 -\u003e 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-\u003ehelper (which runs\ndisable_work), so it can safely flush disable_work on the error path\nwithout deadlock.","modified":"2026-07-15T01:49:03.752457270Z","published":"2026-05-08T14:21:36.692Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43392.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c44198f25fdfecc0ec0fe366bf8a47fe17d8e229"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43392.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43392"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8c2090c504e998c8f34ec870bae71dafcc96a6e0"},{"fixed":"e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b"},{"fixed":"c44198f25fdfecc0ec0fe366bf8a47fe17d8e229"},{"fixed":"05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81"},{"fixed":"b06ccbabe2506fd70b9167a644978b049150224a"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43392.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.12.0"},{"fixed":"6.12.78"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.20"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43392.json"}}],"schema_version":"1.7.5"}