{"id":"DEBIAN-CVE-2026-99205","details":"In the Linux kernel, the following vulnerability has been resolved:  sched/core: Call wakeup_preempt() for queued tasks during class change  Paul reported recent RCU changes exposed a lost resched where CPU idles with a rcutorture thread waiting while being completely runnable.  Dumping the rq state at the time of idling with runnable tasks showed the following:    rq-\u003enext_class = &fair_sched_class   rq-\u003enr_running = 1   rq-\u003ecfs.h_nr_queued = 0   rq-\u003ert.rt_nr_running = 1  Although the waiting task was an RT task, \"rq-\u003enext_class\" did not point to rt_sched_class and was stuck at the lower priority fair_sched_class.  Inspecting sched_change_end() revealed the following race with __sched_setscheduler() for queued, but non-running tasks:      CPU0                                   CPU1     ====                                   ====    __schedule()      /*      * rq-\u003edonor is a fair task that blocks.      * rq-\u003enext_class = &fair_sched_class      */      rq_lock(rq0)      pick_next_task()       /* nr_running = 0 */       pick_task_fair()         sched_balance_newidle()           raw_spin_rq_unlock(rq0)                                     rq_lock(rq0)                                      activate_task(rq0, p)                                       /* p is a fair task */                                       rq0-\u003enr_running++;                                       rq0-\u003ecfs.h_nr_queued++;                                       wakeup_preempt(rq, p)                                         rq-\u003enext_class = &fair_sched_class                                         resched_curr()                                      rq_unlock(rq0)                                      __sched_setscheduler(p)                                       /* p is moved to SCHED_RR */                                       task_rq_lock(p)                                       sched_change_begin()  \t\t\t\t      rq0-\u003ecfs.h_nr_queued--; \t\t\t\t      rq0-\u003ert.rt_nr_running++;                                        sched_change_end()                                         /*                                          * p-\u003eon_rq = 1 (ctx-\u003equeued)                                          * but p is not rq-\u003edonor                                          * (!ctx-\u003erunning) hence                                          * resched_curr() is and                                          * rq-\u003enext_class upgrade is                                          * skipped.                                          */                                         task_rq_unlock()            raw_spin_rq_lock(rq0)            /*            * rq-\u003enr_running = 1            * rq-\u003ecfs.h_nr_queued = 0            * rq-\u003ert.rt_nr_running = 1            * rq-\u003enext_class = &fair_sched_class            */             if (rq-\u003ecfs.h_nr_queued && ...)              /* Above is false */             if (rq_modified_above(this_rq, &fair_sched_class))              /* Also false since rq-\u003enext_class is still fair */        /*        * sched_balance_newidle() is considered to        * have failed to pull any fair tasks and no        * other wakeups were detected.        */        return NULL; /* pick_task_fair() */      pick_task_idle()       return rq-\u003eidle;      next = rq-\u003eidle;      /* Preemption indicators are lost */     clear_tsk_need_resched(prev);     clear_preempt_need_resched();      rq-\u003ecurr = rq-\u003eidle;    !!! rq-\u003eidle switches in with rq-\u003erunning == 1 but !need_resched() !!!  In simple words, enqueue, followed by a class change of the newly queued task goes unnoticed in rq-\u003enext_class indicator and sched_balance_newidle() sees no fair task, nor any higher priority task enqueued.  The above sequence will lead to CPU idling with a runnable task on the CPU.  Call wakeup_preempt() for ctx-\u003equeued cases in sched_change_end() to re-evaluate rq-\u003enext_class after class change (ENQUEUE_CLASS) and set the NEED_RESCHED indicator accordingly.  Newidle balance will correctly see an enqueue of a higher priority t ---truncated---","modified":"2026-10-29T06:00:20.997528263Z","published":"2026-10-28T11:17:41.773Z","upstream":["CVE-2026-99205"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-99205"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.111-1","6.12.113-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.10-1","6.19.10-1~bpo13+1","6.19.11-1","6.19.11-1~bpo13+1","6.19.12-1","6.19.13-1","6.19.13-1~bpo13+1","6.19.14-1","6.19.14-1~bpo13+1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1","7.0-1~exp1","7.0.1-1~exp1","7.0.10-1","7.0.10-1~bpo13+1","7.0.12-1","7.0.12-2","7.0.12-2~bpo13+1","7.0.13-1","7.0.13-1~bpo13+1","7.0.14-1","7.0.3-1","7.0.4-1","7.0.4-1~bpo13+1","7.0.7-1","7.0.7-1~bpo13+1","7.0.9-1","7.0.9-1~bpo13+1","7.1.1-1~exp1","7.1.10-1","7.1.12-1","7.1.13-1","7.1.13-1~bpo13+1","7.1.2-1~exp1","7.1.3-1","7.1.3-1+sunvdc","7.1.3-1~bpo13+1","7.1.4-1","7.1.5-1","7.1.6-1","7.1.7-1","7.1.7-1~bpo13+1","7.1.8-1","7.1.8-1~bpo13+1","7.1.8-2","7.1.9-1","7.1.9-1+sparc64","7.1~rc2-1~exp1","7.1~rc3-1~exp1","7.1~rc4-1~exp1","7.1~rc4-1~exp2","7.1~rc5-1~exp1","7.1~rc7-1~exp1","7.2.10-1","7.2.11-1","7.2.11-1~bpo13+1","7.2.12-1","7.2.13-1","7.2.2-1~exp1","7.2.3-1~exp1","7.2.6-1","7.2.6-1~bpo13+1","7.2.7-1","7.2.8-1","7.2.9-1","7.2.9-1~bpo13+1","7.2~rc3-1~exp1","7.2~rc5-1~exp1","7.2~rc7-1~exp1","7.3~rc6-1~exp1","7.3~rc7-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-99205.json"}}],"schema_version":"1.9.2"}