{"id":"CVE-2026-31733","summary":"sched_ext: Fix stale direct dispatch state in ddsp_dsq_id","details":"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-\u003escx.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().","modified":"2026-07-15T01:49:20.933809175Z","published":"2026-05-01T14:14:31.558Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31733.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7e0ffb72de8aa3b25989c2d980e81b829c577010"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7ea601daa0153e19cd1c6e6b300348c70c05fe77"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ca685511f7afd42cdcbb0feea42e5d332d384251"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31733.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31733"},{"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":"5b26f7b920f76b2b9cc398c252a9e35e44bf5bb9"},{"fixed":"ca685511f7afd42cdcbb0feea42e5d332d384251"},{"fixed":"5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5"},{"fixed":"7ea601daa0153e19cd1c6e6b300348c70c05fe77"},{"fixed":"7e0ffb72de8aa3b25989c2d980e81b829c577010"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31733.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.12.0"},{"fixed":"6.12.82"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.22"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31733.json"}}],"schema_version":"1.7.5"}