Vulnerability-Lookup

GHSA-7564-V46W-3PMR

Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-18 18:32

Details

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

fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()

unregister_fprobe() and unregister_fprobe_async() (used by BPF kprobe-multi) rely on standard RCU grace periods (synchronize_rcu() and call_rcu()) to wait until in-flight fprobe handlers complete before freeing the fprobe.

However, if an fprobe handler executes while RCU is not watching (such as in the idle loop or nohz_full extended quiescent states), standard RCU does not track preemption-disabled sections. Consequently, synchronize_rcu() does not wait for those executions, which can lead to a use-after-free if the fprobe is freed immediately after unregistration. Ensure handlers exit early when !rcu_is_watching().

Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep recursion if probed functions interact with lockdep.

Since rhltable_lookup() and rhl_for_each_entry_rcu() use rcu_dereference_all_check() (which checks rcu_read_lock_any_held()), holding preemption disabled via rcu_read_lock_sched_notrace() is fully valid and sufficient so long as rcu_is_watching() is true.

Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(), fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path rcu_read_lock() and lockdep overhead while guaranteeing safe grace period synchronization.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98861"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:40Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()\n\nunregister_fprobe() and unregister_fprobe_async() (used by BPF\nkprobe-multi) rely on standard RCU grace periods (synchronize_rcu()\nand call_rcu()) to wait until in-flight fprobe handlers complete before\nfreeing the fprobe.\n\nHowever, if an fprobe handler executes while RCU is not watching (such\nas in the idle loop or nohz_full extended quiescent states), standard\nRCU does not track preemption-disabled sections. Consequently,\nsynchronize_rcu() does not wait for those executions, which can lead\nto a use-after-free if the fprobe is freed immediately after\nunregistration. Ensure handlers exit early when !rcu_is_watching().\n\nFurthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously\nused guard(rcu)() and rcu_read_lock(), which invoke lockdep on every\nhit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep\nrecursion if probed functions interact with lockdep.\n\nSince rhltable_lookup() and rhl_for_each_entry_rcu() use\nrcu_dereference_all_check() (which checks rcu_read_lock_any_held()),\nholding preemption disabled via rcu_read_lock_sched_notrace() is fully\nvalid and sufficient so long as rcu_is_watching() is true.\n\nDefine and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(),\nfprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path\nrcu_read_lock() and lockdep overhead while guaranteeing safe grace\nperiod synchronization.",
  "id": "GHSA-7564-v46w-3pmr",
  "modified": "2026-10-18T18:32:06Z",
  "published": "2026-10-18T18:32:06Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98861"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a85d0f00671b4d4527317c10ba018680f7d8d673"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dd4a0d4993633b45470abf6da4ea0ca563402245"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e0a6249190402a28f1e2925a81acf573157d55ef"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98861 (GCVE-0-2026-98861)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:51 – Updated: 2026-10-18 15:51

Title

fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()

Summary

In the Linux kernel, the following vulnerability has been resolved: fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() unregister_fprobe() and unregister_fprobe_async() (used by BPF kprobe-multi) rely on standard RCU grace periods (synchronize_rcu() and call_rcu()) to wait until in-flight fprobe handlers complete before freeing the fprobe. However, if an fprobe handler executes while RCU is not watching (such as in the idle loop or nohz_full extended quiescent states), standard RCU does not track preemption-disabled sections. Consequently, synchronize_rcu() does not wait for those executions, which can lead to a use-after-free if the fprobe is freed immediately after unregistration. Ensure handlers exit early when !rcu_is_watching(). Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep recursion if probed functions interact with lockdep. Since rhltable_lookup() and rhl_for_each_entry_rcu() use rcu_dereference_all_check() (which checks rcu_read_lock_any_held()), holding preemption disabled via rcu_read_lock_sched_notrace() is fully valid and sufficient so long as rcu_is_watching() is true. Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(), fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path rcu_read_lock() and lockdep overhead while guaranteeing safe grace period synchronization.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7100 records in the last 180 days details

References

3 references

URL	Tags
https://git.kernel.org/stable/c/a85d0f00671b4d452…
https://git.kernel.org/stable/c/dd4a0d4993633b454…
https://git.kernel.org/stable/c/e0a6249190402a28f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 56b4cfcf1518245493c60fd39c56978f508f1816 , < a85d0f00671b4d4527317c10ba018680f7d8d673 (git) Affected: 657b594b2084b39a4bc6d8493aa2140cb00cea49 , < dd4a0d4993633b45470abf6da4ea0ca563402245 (git) Affected: 657b594b2084b39a4bc6d8493aa2140cb00cea49 , < e0a6249190402a28f1e2925a81acf573157d55ef (git) Affected: a4f6a9005ed6cfd360ef2520430927f05f92ffb0 (git) Affected: 6.18.34 , < 6.18.56 (semver) Affected: 7.0.11 , < 7.1 (semver)
Linux	Linux	Affected: 7.1 Unaffected: 0 , < 7.1 (semver) Unaffected: 6.18.56 , ≤ 6.18.* (semver) Unaffected: 7.2.10 , ≤ 7.2.* (semver) Unaffected: 7.3-rc6 , ≤ * (original_commit_for_fix)

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JSON

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        {
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            "kernel/trace/fprobe.c"
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}

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.

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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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