{"id":"CVE-2026-31733","state":"PUBLISHED","title":"sched_ext: Fix stale direct dispatch state in ddsp_dsq_id","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix stale direct dispatch state in ddsp_dsq_id\n\n@p->scx.ddsp_dsq_id can be left set (non-SCX_DSQ_INVALID) triggering a\nspurious warning in mark_direct_dispatch() when the next wakeup's\nops.select_cpu() calls scx_bpf_dsq_insert(), such as:\n\n WARNING: kernel/sched/ext.c:1273 at scx_dsq_insert_commit+0xcd/0x140\n\nThe root cause is that ddsp_dsq_id was only cleared in dispatch_enqueue(),\nwhich is not reached in all paths that consume or cancel a direct dispatch\nverdict.\n\nFix it by clearing it at the right places:\n\n - direct_dispatch(): cache the direct dispatch state in local variables\n   and clear it before dispatch_enqueue() on the synchronous path. For\n   the deferred path, the direct dispatch state must remain set until\n   process_ddsp_deferred_locals() consumes them.\n\n - process_ddsp_deferred_locals(): cache the dispatch state in local\n   variables and clear it before calling dispatch_to_local_dsq(), which\n   may migrate the task to another rq.\n\n - do_enqueue_task(): clear the dispatch state on the enqueue path\n   (local/global/bypass fallbacks), where the direct dispatch verdict is\n   ignored.\n\n - dequeue_task_scx(): clear the dispatch state after dispatch_dequeue()\n   to handle both the deferred dispatch cancellation and the holding_cpu\n   race, covering all cases where a pending direct dispatch is\n   cancelled.\n\n - scx_disable_task(): clear the direct dispatch state when\n   transitioning a task out of the current scheduler. Waking tasks may\n   have had the direct dispatch state set by the outgoing scheduler's\n   ops.select_cpu() and then been queued on a wake_list via\n   ttwu_queue_wakelist(), when SCX_OPS_ALLOW_QUEUED_WAKEUP is set. Such\n   tasks are not on the runqueue and are not iterated by scx_bypass(),\n   so their direct dispatch state won't be cleared. Without this clear,\n   any subsequent SCX scheduler that tries to direct dispatch the task\n   will trigger the WARN_ON_ONCE() in mark_direct_dispatch().","publishedAt":"2026-05-01T14:14:31.558Z","updatedAt":"2026-05-11T22:14:42.580Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"ca685511f7afd42cdcbb0feea42e5d332d384251","versionType":"git"},{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5","versionType":"git"},{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"7ea601daa0153e19cd1c6e6b300348c70c05fe77","versionType":"git"},{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"7e0ffb72de8aa3b25989c2d980e81b829c577010","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":"6.12.82","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.22","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.12","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/ca685511f7afd42cdcbb0feea42e5d332d384251","https://git.kernel.org/stable/c/5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5","https://git.kernel.org/stable/c/7ea601daa0153e19cd1c6e6b300348c70c05fe77","https://git.kernel.org/stable/c/7e0ffb72de8aa3b25989c2d980e81b829c577010"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31733.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31733","state":"PUBLISHED","datePublished":"2026-05-01T14:14:31.558Z","dateUpdated":"2026-05-11T22:14:42.580Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.137Z"},"containers":{"cna":{"title":"sched_ext: Fix stale direct dispatch state in ddsp_dsq_id","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix stale direct dispatch state in ddsp_dsq_id\n\n@p->scx.ddsp_dsq_id can be left set (non-SCX_DSQ_INVALID) triggering a\nspurious warning in mark_direct_dispatch() when the next wakeup's\nops.select_cpu() calls scx_bpf_dsq_insert(), such as:\n\n WARNING: kernel/sched/ext.c:1273 at scx_dsq_insert_commit+0xcd/0x140\n\nThe root cause is that ddsp_dsq_id was only cleared in dispatch_enqueue(),\nwhich is not reached in all paths that consume or cancel a direct dispatch\nverdict.\n\nFix it by clearing it at the right places:\n\n - direct_dispatch(): cache the direct dispatch state in local variables\n   and clear it before dispatch_enqueue() on the synchronous path. For\n   the deferred path, the direct dispatch state must remain set until\n   process_ddsp_deferred_locals() consumes them.\n\n - process_ddsp_deferred_locals(): cache the dispatch state in local\n   variables and clear it before calling dispatch_to_local_dsq(), which\n   may migrate the task to another rq.\n\n - do_enqueue_task(): clear the dispatch state on the enqueue path\n   (local/global/bypass fallbacks), where the direct dispatch verdict is\n   ignored.\n\n - dequeue_task_scx(): clear the dispatch state after dispatch_dequeue()\n   to handle both the deferred dispatch cancellation and the holding_cpu\n   race, covering all cases where a pending direct dispatch is\n   cancelled.\n\n - scx_disable_task(): clear the direct dispatch state when\n   transitioning a task out of the current scheduler. Waking tasks may\n   have had the direct dispatch state set by the outgoing scheduler's\n   ops.select_cpu() and then been queued on a wake_list via\n   ttwu_queue_wakelist(), when SCX_OPS_ALLOW_QUEUED_WAKEUP is set. Such\n   tasks are not on the runqueue and are not iterated by scx_bypass(),\n   so their direct dispatch state won't be cleared. Without this clear,\n   any subsequent SCX scheduler that tries to direct dispatch the task\n   will trigger the WARN_ON_ONCE() in mark_direct_dispatch()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"ca685511f7afd42cdcbb0feea42e5d332d384251","versionType":"git"},{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5","versionType":"git"},{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"7ea601daa0153e19cd1c6e6b300348c70c05fe77","versionType":"git"},{"version":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9","status":"affected","lessThan":"7e0ffb72de8aa3b25989c2d980e81b829c577010","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":"6.12.82","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.22","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.12","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/ca685511f7afd42cdcbb0feea42e5d332d384251"},{"url":"https://git.kernel.org/stable/c/5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5"},{"url":"https://git.kernel.org/stable/c/7ea601daa0153e19cd1c6e6b300348c70c05fe77"},{"url":"https://git.kernel.org/stable/c/7e0ffb72de8aa3b25989c2d980e81b829c577010"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:14:42.580Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.12.82"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.18.22"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.19.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}