GHSA-84WX-7549-84G8
Vulnerability from github – Published: 2026-05-01 15:30 – Updated: 2026-05-07 18:30In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix stale direct dispatch state in ddsp_dsq_id
@p->scx.ddsp_dsq_id can be left set (non-SCX_DSQ_INVALID) triggering a spurious warning in mark_direct_dispatch() when the next wakeup's ops.select_cpu() calls scx_bpf_dsq_insert(), such as:
WARNING: kernel/sched/ext.c:1273 at scx_dsq_insert_commit+0xcd/0x140
The root cause is that ddsp_dsq_id was only cleared in dispatch_enqueue(), which is not reached in all paths that consume or cancel a direct dispatch verdict.
Fix it by clearing it at the right places:
-
direct_dispatch(): cache the direct dispatch state in local variables and clear it before dispatch_enqueue() on the synchronous path. For the deferred path, the direct dispatch state must remain set until process_ddsp_deferred_locals() consumes them.
-
process_ddsp_deferred_locals(): cache the dispatch state in local variables and clear it before calling dispatch_to_local_dsq(), which may migrate the task to another rq.
-
do_enqueue_task(): clear the dispatch state on the enqueue path (local/global/bypass fallbacks), where the direct dispatch verdict is ignored.
-
dequeue_task_scx(): clear the dispatch state after dispatch_dequeue() to handle both the deferred dispatch cancellation and the holding_cpu race, covering all cases where a pending direct dispatch is cancelled.
-
scx_disable_task(): clear the direct dispatch state when transitioning a task out of the current scheduler. Waking tasks may have had the direct dispatch state set by the outgoing scheduler's ops.select_cpu() and then been queued on a wake_list via ttwu_queue_wakelist(), when SCX_OPS_ALLOW_QUEUED_WAKEUP is set. Such tasks are not on the runqueue and are not iterated by scx_bypass(), so their direct dispatch state won't be cleared. Without this clear, any subsequent SCX scheduler that tries to direct dispatch the task will trigger the WARN_ON_ONCE() in mark_direct_dispatch().
{
"affected": [],
"aliases": [
"CVE-2026-31733"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-01T15:16:35Z",
"severity": "MODERATE"
},
"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\u0027s\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\u0027s\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\u0027t 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().",
"id": "GHSA-84wx-7549-84g8",
"modified": "2026-05-07T18:30:34Z",
"published": "2026-05-01T15:30:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31733"
},
{
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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