122 lines
8.8 KiB
JSON
122 lines
8.8 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-99205",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-25T10:25:14.401Z",
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"datePublished": "2026-10-28T10:35:59.093Z",
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"dateUpdated": "2026-10-28T10:35:59.093Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-28T10:35:59.093Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/core: Call wakeup_preempt() for queued tasks during class change\n\nPaul reported recent RCU changes exposed a lost resched where CPU idles\nwith a rcutorture thread waiting while being completely runnable.\n\nDumping the rq state at the time of idling with runnable tasks showed\nthe following:\n\n rq->next_class = &fair_sched_class\n rq->nr_running = 1\n rq->cfs.h_nr_queued = 0\n rq->rt.rt_nr_running = 1\n\nAlthough the waiting task was an RT task, \"rq->next_class\" did not point\nto rt_sched_class and was stuck at the lower priority fair_sched_class.\n\nInspecting sched_change_end() revealed the following race with\n__sched_setscheduler() for queued, but non-running tasks:\n\n CPU0 CPU1\n ==== ====\n\n __schedule()\n\n /*\n * rq->donor is a fair task that blocks.\n * rq->next_class = &fair_sched_class\n */\n\n rq_lock(rq0)\n\n pick_next_task()\n /* nr_running = 0 */\n pick_task_fair()\n sched_balance_newidle()\n raw_spin_rq_unlock(rq0)\n rq_lock(rq0)\n\n activate_task(rq0, p)\n /* p is a fair task */\n rq0->nr_running++;\n rq0->cfs.h_nr_queued++;\n wakeup_preempt(rq, p)\n rq->next_class = &fair_sched_class\n resched_curr()\n\n rq_unlock(rq0)\n\n __sched_setscheduler(p)\n /* p is moved to SCHED_RR */\n task_rq_lock(p)\n sched_change_begin()\n\n\t\t\t\t rq0->cfs.h_nr_queued--;\n\t\t\t\t rq0->rt.rt_nr_running++;\n\n sched_change_end()\n /*\n * p->on_rq = 1 (ctx->queued)\n * but p is not rq->donor\n * (!ctx->running) hence\n * resched_curr() is and\n * rq->next_class upgrade is\n * skipped.\n */\n\n task_rq_unlock()\n\n raw_spin_rq_lock(rq0)\n\n /*\n * rq->nr_running = 1\n * rq->cfs.h_nr_queued = 0\n * rq->rt.rt_nr_running = 1\n * rq->next_class = &fair_sched_class\n */\n\n if (rq->cfs.h_nr_queued && ...)\n /* Above is false */\n\n if (rq_modified_above(this_rq, &fair_sched_class))\n /* Also false since rq->next_class is still fair */\n\n /*\n * sched_balance_newidle() is considered to\n * have failed to pull any fair tasks and no\n * other wakeups were detected.\n */\n return NULL; /* pick_task_fair() */\n\n pick_task_idle()\n return rq->idle;\n\n next = rq->idle;\n\n /* Preemption indicators are lost */\n clear_tsk_need_resched(prev);\n clear_preempt_need_resched();\n\n rq->curr = rq->idle;\n\n !!! rq->idle switches in with rq->running == 1 but !need_resched() !!!\n\nIn simple words, enqueue, followed by a class change of the newly queued\ntask goes unnoticed in rq->next_class indicator and\nsched_balance_newidle() sees no fair task, nor any higher priority task\nenqueued.\n\nThe above sequence will lead to CPU idling with a runnable task on the\nCPU.\n\nCall wakeup_preempt() for ctx->queued cases in sched_change_end() to\nre-evaluate rq->next_class after class change (ENQUEUE_CLASS) and set\nthe NEED_RESCHED indicator accordingly.\n\nNewidle balance will correctly see an enqueue of a higher priority\nt\n---truncated---"
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"kernel/sched/core.c"
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],
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"versions": [
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{
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"version": "704069649b5bfb7bf1fe32c0281fe9036806a59a",
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"lessThan": "ae89744c5ebf299bf55ac7581768fbd9f119a903",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "704069649b5bfb7bf1fe32c0281fe9036806a59a",
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"lessThan": "118a2cf4ced60777a2408001e2b4838fed1cea55",
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"status": "affected",
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"versionType": "git"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"kernel/sched/core.c"
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],
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"versions": [
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{
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"version": "7.0",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "7.0",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2.13",
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"lessThanOrEqual": "7.2.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.3",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "7.0",
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"versionEndExcluding": "7.2.13"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "7.0",
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"versionEndExcluding": "7.3"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/ae89744c5ebf299bf55ac7581768fbd9f119a903"
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},
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{
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"url": "https://git.kernel.org/stable/c/118a2cf4ced60777a2408001e2b4838fed1cea55"
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}
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],
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"title": "sched/core: Call wakeup_preempt() for queued tasks during class change",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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}
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} |