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GHSA-H6HX-XPP5-6VC3

Vulnerability from github – Published: 2026-10-06 09:31 – Updated: 2026-10-06 09:31

Details

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Fix NULL sched deref in kfunc sub-sched error paths

When the root scheduler has sub-scheds attached, the COMPAT kfunc wrappers scx_bpf_select_cpu_and() and scx_bpf_dsq_insert_vtime() refuse the call and report to @p's scheduler:

scx_error(scx_task_sched(p), "... must be used");

The wrappers are reachable with tasks that have no scheduler. scx_bpf_select_cpu_and() is in the select_cpu kfunc group, which scx_kfunc_context_filter() opens to BPF_PROG_TYPE_SYSCALL programs; scx_bpf_dsq_insert_vtime() is in the enqueue_dispatch group, which ops.enqueue() and ops.dispatch() may call with any KF_RCU task -- the group has no kf_tasks validation, and scx_dsq_insert_preamble() checks task ownership with scx_task_on_sched() precisely because @p may be an arbitrary task.

scx_task_sched(p) is p->scx.sched, which is NULL for tasks past sched_ext_dead() -- which clears it via scx_disable_and_exit_task() on exit -- and for idle tasks, which the enable paths skip as they are never scheduled through SCX. It is also an rcu_dereference_protected() that expects @p's pi_lock or rq lock, which neither wrapper holds. Passing NULL to scx_error() reaches scx_vexit(), which dereferences sch->exit_info, oopsing the kernel.

One concrete trigger exercised while developing the fix: a BPF_PROG_TYPE_SYSCALL program calling the select_cpu_and wrapper on an exited-but-not-reaped task while a sub-scheduler was attached (its pid stays findable while the zombie is unreaped; faulting instruction is the scx_vexit() prologue "mov r15,[rdi+0x398]" with RDI=NULL and 0x398 the offset of sch->exit_info):

sched_ext: BPF scheduler "kfunc_subsched_null" enabled sched_ext: BPF sub-scheduler "kfunc_subsched_null" enabled sched_ext: Unassociated program run_select_cpu_ (id 76) BUG: kernel NULL pointer dereference, address: 0000000000000398 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP NOPTI CPU: 7 UID: 0 PID: 8201 Comm: kfunc_test_runn Tainted: G W RIP: 0010:scx_vexit+0x25/0xa0 Code: ... <4c> 8b bf 98 03 00 00 ... CR2: 0000000000000398 Call Trace: __scx_exit+0x4f/0x70 scx_bpf_select_cpu_and+0xab/0xb0 bpf_prog_430ed61a7b66e03a_run_select_cpu_and+0x9c/0xe7 ? __x64_sys_bpf+0x2c/0x40 bpf_prog_test_run_syscall+0x130/0x2f0 __sys_bpf+0x930/0x10d0 ? __x64_sys_bpf+0x2c/0x40 __x64_sys_bpf+0x2c/0x40 do_syscall_64+0xbc/0x460 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Read @p's scheduler under RCU instead, which the wrappers can do from their guard(rcu)(): fault it when it can be determined, and when it can't be determined -- @p is a task past sched_ext_dead() or an idle task -- there is nothing obviously wrong to report, so just refuse the call as before without faulting any scheduler.

These COMPAT wrappers are scheduled for eventual removal once the deprecation grace period elapses, but until then -- and regardless of their removal timeline -- they must not oops the kernel on a task they are handed.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98220"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-06T09:18:08Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix NULL sched deref in kfunc sub-sched error paths\n\nWhen the root scheduler has sub-scheds attached, the COMPAT kfunc\nwrappers scx_bpf_select_cpu_and() and scx_bpf_dsq_insert_vtime() refuse\nthe call and report to @p\u0027s scheduler:\n\n\tscx_error(scx_task_sched(p), \"... must be used\");\n\nThe wrappers are reachable with tasks that have no scheduler.\nscx_bpf_select_cpu_and() is in the select_cpu kfunc group, which\nscx_kfunc_context_filter() opens to BPF_PROG_TYPE_SYSCALL programs;\nscx_bpf_dsq_insert_vtime() is in the enqueue_dispatch group, which\nops.enqueue() and ops.dispatch() may call with any KF_RCU task -- the\ngroup has no kf_tasks validation, and scx_dsq_insert_preamble() checks\ntask ownership with scx_task_on_sched() precisely because @p may be an\narbitrary task.\n\nscx_task_sched(p) is p-\u003escx.sched, which is NULL for tasks past\nsched_ext_dead() -- which clears it via scx_disable_and_exit_task() on\nexit -- and for idle tasks, which the enable paths skip as they are\nnever scheduled through SCX. It is also an rcu_dereference_protected()\nthat expects @p\u0027s pi_lock or rq lock, which neither wrapper holds.\nPassing NULL to scx_error() reaches scx_vexit(), which dereferences\nsch-\u003eexit_info, oopsing the kernel.\n\nOne concrete trigger exercised while developing the fix: a\nBPF_PROG_TYPE_SYSCALL program calling the select_cpu_and wrapper on an\nexited-but-not-reaped task while a sub-scheduler was attached (its pid\nstays findable while the zombie is unreaped; faulting instruction is\nthe scx_vexit() prologue \"mov r15,[rdi+0x398]\" with RDI=NULL and 0x398\nthe offset of sch-\u003eexit_info):\n\n  sched_ext: BPF scheduler \"kfunc_subsched_null\" enabled\n  sched_ext: BPF sub-scheduler \"kfunc_subsched_null\" enabled\n  sched_ext: Unassociated program run_select_cpu_ (id 76)\n  BUG: kernel NULL pointer dereference, address: 0000000000000398\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  Oops: Oops: 0000 [#1] SMP NOPTI\n  CPU: 7 UID: 0 PID: 8201 Comm: kfunc_test_runn Tainted: G W\n  RIP: 0010:scx_vexit+0x25/0xa0\n  Code: ... \u003c4c\u003e 8b bf 98 03 00 00 ...\n  CR2: 0000000000000398\n  Call Trace:\n   \u003cTASK\u003e\n   __scx_exit+0x4f/0x70\n   scx_bpf_select_cpu_and+0xab/0xb0\n   bpf_prog_430ed61a7b66e03a_run_select_cpu_and+0x9c/0xe7\n   ? __x64_sys_bpf+0x2c/0x40\n   bpf_prog_test_run_syscall+0x130/0x2f0\n   __sys_bpf+0x930/0x10d0\n   ? __x64_sys_bpf+0x2c/0x40\n   __x64_sys_bpf+0x2c/0x40\n   do_syscall_64+0xbc/0x460\n   entry_SYSCALL_64_after_hwframe+0x76/0x7e\n   \u003c/TASK\u003e\n\nRead @p\u0027s scheduler under RCU instead, which the wrappers can do from\ntheir guard(rcu)(): fault it when it can be determined, and when it\ncan\u0027t be determined -- @p is a task past sched_ext_dead() or an idle\ntask -- there is nothing obviously wrong to report, so just refuse the\ncall as before without faulting any scheduler.\n\nThese COMPAT wrappers are scheduled for eventual removal once the\ndeprecation grace period elapses, but until then -- and regardless of\ntheir removal timeline -- they must not oops the kernel on a task they\nare handed.",
  "id": "GHSA-h6hx-xpp5-6vc3",
  "modified": "2026-10-06T09:31:31Z",
  "published": "2026-10-06T09:31:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98220"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0a85182723b65ad8bee8131bc38fcf0347d6679b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/589f0945bf3ebf0790fd51e28c7f0d04ed3d8b78"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98220 (GCVE-0-2026-98220)

Vulnerability from cvelistv5 – Published: 2026-10-06 08:44 – Updated: 2026-10-06 08:44

Title

sched_ext: Fix NULL sched deref in kfunc sub-sched error paths

Summary

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix NULL sched deref in kfunc sub-sched error paths When the root scheduler has sub-scheds attached, the COMPAT kfunc wrappers scx_bpf_select_cpu_and() and scx_bpf_dsq_insert_vtime() refuse the call and report to @p's scheduler: scx_error(scx_task_sched(p), "... must be used"); The wrappers are reachable with tasks that have no scheduler. scx_bpf_select_cpu_and() is in the select_cpu kfunc group, which scx_kfunc_context_filter() opens to BPF_PROG_TYPE_SYSCALL programs; scx_bpf_dsq_insert_vtime() is in the enqueue_dispatch group, which ops.enqueue() and ops.dispatch() may call with any KF_RCU task -- the group has no kf_tasks validation, and scx_dsq_insert_preamble() checks task ownership with scx_task_on_sched() precisely because @p may be an arbitrary task. scx_task_sched(p) is p->scx.sched, which is NULL for tasks past sched_ext_dead() -- which clears it via scx_disable_and_exit_task() on exit -- and for idle tasks, which the enable paths skip as they are never scheduled through SCX. It is also an rcu_dereference_protected() that expects @p's pi_lock or rq lock, which neither wrapper holds. Passing NULL to scx_error() reaches scx_vexit(), which dereferences sch->exit_info, oopsing the kernel. One concrete trigger exercised while developing the fix: a BPF_PROG_TYPE_SYSCALL program calling the select_cpu_and wrapper on an exited-but-not-reaped task while a sub-scheduler was attached (its pid stays findable while the zombie is unreaped; faulting instruction is the scx_vexit() prologue "mov r15,[rdi+0x398]" with RDI=NULL and 0x398 the offset of sch->exit_info): sched_ext: BPF scheduler "kfunc_subsched_null" enabled sched_ext: BPF sub-scheduler "kfunc_subsched_null" enabled sched_ext: Unassociated program run_select_cpu_ (id 76) BUG: kernel NULL pointer dereference, address: 0000000000000398 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP NOPTI CPU: 7 UID: 0 PID: 8201 Comm: kfunc_test_runn Tainted: G W RIP: 0010:scx_vexit+0x25/0xa0 Code: ... <4c> 8b bf 98 03 00 00 ... CR2: 0000000000000398 Call Trace: <TASK> __scx_exit+0x4f/0x70 scx_bpf_select_cpu_and+0xab/0xb0 bpf_prog_430ed61a7b66e03a_run_select_cpu_and+0x9c/0xe7 ? __x64_sys_bpf+0x2c/0x40 bpf_prog_test_run_syscall+0x130/0x2f0 __sys_bpf+0x930/0x10d0 ? __x64_sys_bpf+0x2c/0x40 __x64_sys_bpf+0x2c/0x40 do_syscall_64+0xbc/0x460 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> Read @p's scheduler under RCU instead, which the wrappers can do from their guard(rcu)(): fault it when it can be determined, and when it can't be determined -- @p is a task past sched_ext_dead() or an idle task -- there is nothing obviously wrong to report, so just refuse the call as before without faulting any scheduler. These COMPAT wrappers are scheduled for eventual removal once the deprecation grace period elapses, but until then -- and regardless of their removal timeline -- they must not oops the kernel on a task they are handed.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6664 records in the last 180 days details

References

2 references

URL	Tags
https://git.kernel.org/stable/c/589f0945bf3ebf079…
https://git.kernel.org/stable/c/0a85182723b65ad8b…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: a5fa0708cbfda4d3c2c6a447de7c4b0b23595527 , < 589f0945bf3ebf0790fd51e28c7f0d04ed3d8b78 (git) Affected: a5fa0708cbfda4d3c2c6a447de7c4b0b23595527 , < 0a85182723b65ad8bee8131bc38fcf0347d6679b (git)
Linux	Linux	Affected: 7.1 Unaffected: 0 , < 7.1 (semver) Unaffected: 7.2.8 , ≤ 7.2.* (semver) Unaffected: 7.3-rc4 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/ext.c",
            "kernel/sched/ext/idle.c"
          ],
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          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "589f0945bf3ebf0790fd51e28c7f0d04ed3d8b78",
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              "version": "a5fa0708cbfda4d3c2c6a447de7c4b0b23595527",
              "versionType": "git"
            },
            {
              "lessThan": "0a85182723b65ad8bee8131bc38fcf0347d6679b",
              "status": "affected",
              "version": "a5fa0708cbfda4d3c2c6a447de7c4b0b23595527",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/ext.c",
            "kernel/sched/ext/idle.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc4",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.8",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                }
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              "negate": false,
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix NULL sched deref in kfunc sub-sched error paths\n\nWhen the root scheduler has sub-scheds attached, the COMPAT kfunc\nwrappers scx_bpf_select_cpu_and() and scx_bpf_dsq_insert_vtime() refuse\nthe call and report to @p\u0027s scheduler:\n\n\tscx_error(scx_task_sched(p), \"... must be used\");\n\nThe wrappers are reachable with tasks that have no scheduler.\nscx_bpf_select_cpu_and() is in the select_cpu kfunc group, which\nscx_kfunc_context_filter() opens to BPF_PROG_TYPE_SYSCALL programs;\nscx_bpf_dsq_insert_vtime() is in the enqueue_dispatch group, which\nops.enqueue() and ops.dispatch() may call with any KF_RCU task -- the\ngroup has no kf_tasks validation, and scx_dsq_insert_preamble() checks\ntask ownership with scx_task_on_sched() precisely because @p may be an\narbitrary task.\n\nscx_task_sched(p) is p-\u003escx.sched, which is NULL for tasks past\nsched_ext_dead() -- which clears it via scx_disable_and_exit_task() on\nexit -- and for idle tasks, which the enable paths skip as they are\nnever scheduled through SCX. It is also an rcu_dereference_protected()\nthat expects @p\u0027s pi_lock or rq lock, which neither wrapper holds.\nPassing NULL to scx_error() reaches scx_vexit(), which dereferences\nsch-\u003eexit_info, oopsing the kernel.\n\nOne concrete trigger exercised while developing the fix: a\nBPF_PROG_TYPE_SYSCALL program calling the select_cpu_and wrapper on an\nexited-but-not-reaped task while a sub-scheduler was attached (its pid\nstays findable while the zombie is unreaped; faulting instruction is\nthe scx_vexit() prologue \"mov r15,[rdi+0x398]\" with RDI=NULL and 0x398\nthe offset of sch-\u003eexit_info):\n\n  sched_ext: BPF scheduler \"kfunc_subsched_null\" enabled\n  sched_ext: BPF sub-scheduler \"kfunc_subsched_null\" enabled\n  sched_ext: Unassociated program run_select_cpu_ (id 76)\n  BUG: kernel NULL pointer dereference, address: 0000000000000398\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  Oops: Oops: 0000 [#1] SMP NOPTI\n  CPU: 7 UID: 0 PID: 8201 Comm: kfunc_test_runn Tainted: G W\n  RIP: 0010:scx_vexit+0x25/0xa0\n  Code: ... \u003c4c\u003e 8b bf 98 03 00 00 ...\n  CR2: 0000000000000398\n  Call Trace:\n   \u003cTASK\u003e\n   __scx_exit+0x4f/0x70\n   scx_bpf_select_cpu_and+0xab/0xb0\n   bpf_prog_430ed61a7b66e03a_run_select_cpu_and+0x9c/0xe7\n   ? __x64_sys_bpf+0x2c/0x40\n   bpf_prog_test_run_syscall+0x130/0x2f0\n   __sys_bpf+0x930/0x10d0\n   ? __x64_sys_bpf+0x2c/0x40\n   __x64_sys_bpf+0x2c/0x40\n   do_syscall_64+0xbc/0x460\n   entry_SYSCALL_64_after_hwframe+0x76/0x7e\n   \u003c/TASK\u003e\n\nRead @p\u0027s scheduler under RCU instead, which the wrappers can do from\ntheir guard(rcu)(): fault it when it can be determined, and when it\ncan\u0027t be determined -- @p is a task past sched_ext_dead() or an idle\ntask -- there is nothing obviously wrong to report, so just refuse the\ncall as before without faulting any scheduler.\n\nThese COMPAT wrappers are scheduled for eventual removal once the\ndeprecation grace period elapses, but until then -- and regardless of\ntheir removal timeline -- they must not oops the kernel on a task they\nare handed."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-06T08:44:55.843Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/589f0945bf3ebf0790fd51e28c7f0d04ed3d8b78"
        },
        {
          "url": "https://git.kernel.org/stable/c/0a85182723b65ad8bee8131bc38fcf0347d6679b"
        }
      ],
      "title": "sched_ext: Fix NULL sched deref in kfunc sub-sched error paths",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98220",
    "datePublished": "2026-10-06T08:44:55.843Z",
    "dateReserved": "2026-09-25T10:25:14.327Z",
    "dateUpdated": "2026-10-06T08:44:55.843Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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