Vulnerability-Lookup

GHSA-H7C8-WRGV-C7F2

Vulnerability from github – Published: 2026-07-19 12:30 – Updated: 2026-07-19 12:30

Details

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

gfs2: fix use-after-free in gfs2_qd_dealloc

gfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(), accesses the superblock object sdp through qd->qd_sbd after freeing qd. It does so to decrement sd_quota_count and wake up sd_kill_wait.

However, by the time the RCU callback runs, gfs2_put_super() may have already freed sdp via free_sbd(). This can happen when gfs2_quota_cleanup() is called during unmount: it disposes of quota objects via call_rcu() and then waits on sd_kill_wait with a 60-second timeout. If the timeout expires, or if gfs2_gl_hash_clear() triggers additional qd_put() calls that schedule more RCU callbacks after the wait completes, gfs2_put_super() will proceed to free the superblock while RCU callbacks referencing it are still pending.

Add an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure all pending RCU callbacks (including gfs2_qd_dealloc) have completed before the superblock is freed.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-63804"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T12:16:53Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ngfs2: fix use-after-free in gfs2_qd_dealloc\n\ngfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(),\naccesses the superblock object sdp through qd-\u003eqd_sbd after freeing qd.\nIt does so to decrement sd_quota_count and wake up sd_kill_wait.\n\nHowever, by the time the RCU callback runs, gfs2_put_super() may have\nalready freed sdp via free_sbd().  This can happen when\ngfs2_quota_cleanup() is called during unmount: it disposes of quota\nobjects via call_rcu() and then waits on sd_kill_wait with a 60-second\ntimeout.  If the timeout expires, or if gfs2_gl_hash_clear() triggers\nadditional qd_put() calls that schedule more RCU callbacks after the\nwait completes, gfs2_put_super() will proceed to free the superblock\nwhile RCU callbacks referencing it are still pending.\n\nAdd an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure\nall pending RCU callbacks (including gfs2_qd_dealloc) have completed\nbefore the superblock is freed.",
  "id": "GHSA-h7c8-wrgv-c7f2",
  "modified": "2026-07-19T12:30:23Z",
  "published": "2026-07-19T12:30:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63804"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4fe388218826df8607ae41a6305df67db08a9093"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8745d9f7e1682c39f0a1578895ac74205e2a6757"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f9c9ec2c319f843b70ecdf939d48b52d189bc081"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-63804 (GCVE-0-2026-63804)

Vulnerability from cvelistv5 – Published: 2026-07-19 12:02 – Updated: 2026-07-19 12:02

Title

gfs2: fix use-after-free in gfs2_qd_dealloc

Summary

In the Linux kernel, the following vulnerability has been resolved: gfs2: fix use-after-free in gfs2_qd_dealloc gfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(), accesses the superblock object sdp through qd->qd_sbd after freeing qd. It does so to decrement sd_quota_count and wake up sd_kill_wait. However, by the time the RCU callback runs, gfs2_put_super() may have already freed sdp via free_sbd(). This can happen when gfs2_quota_cleanup() is called during unmount: it disposes of quota objects via call_rcu() and then waits on sd_kill_wait with a 60-second timeout. If the timeout expires, or if gfs2_gl_hash_clear() triggers additional qd_put() calls that schedule more RCU callbacks after the wait completes, gfs2_put_super() will proceed to free the superblock while RCU callbacks referencing it are still pending. Add an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure all pending RCU callbacks (including gfs2_qd_dealloc) have completed before the superblock is freed.

Severity

No CVSS data available.

Assigner

Linux

References

5 references

URL	Tags
https://git.kernel.org/stable/c/4fe388218826df860…
https://git.kernel.org/stable/c/8745d9f7e1682c39f…
https://git.kernel.org/stable/c/b85ef03f726b15047…
https://git.kernel.org/stable/c/9d0d5ba20cad661f7…
https://git.kernel.org/stable/c/f9c9ec2c319f843b7…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: a475c5dd16e57c570113eccba51955b5df8bb052 , < 4fe388218826df8607ae41a6305df67db08a9093 (git) Affected: a475c5dd16e57c570113eccba51955b5df8bb052 , < 8745d9f7e1682c39f0a1578895ac74205e2a6757 (git) Affected: a475c5dd16e57c570113eccba51955b5df8bb052 , < b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0 (git) Affected: a475c5dd16e57c570113eccba51955b5df8bb052 , < 9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0 (git) Affected: a475c5dd16e57c570113eccba51955b5df8bb052 , < f9c9ec2c319f843b70ecdf939d48b52d189bc081 (git)
Linux	Linux	Affected: 6.6 Unaffected: 0 , < 6.6 (semver) Unaffected: 6.6.144 , ≤ 6.6.* (semver) Unaffected: 6.12.95 , ≤ 6.12.* (semver) Unaffected: 6.18.38 , ≤ 6.18.* (semver) Unaffected: 7.1.3 , ≤ 7.1.* (semver) Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)

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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/gfs2/super.c"
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          "defaultStatus": "affected",
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.38",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.144",
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                },
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                {
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        },
        {
          "url": "https://git.kernel.org/stable/c/f9c9ec2c319f843b70ecdf939d48b52d189bc081"
        }
      ],
      "title": "gfs2: fix use-after-free in gfs2_qd_dealloc",
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    "cveId": "CVE-2026-63804",
    "datePublished": "2026-07-19T12:02:09.111Z",
    "dateReserved": "2026-07-19T07:54:57.013Z",
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    "state": "PUBLISHED"
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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.

Detection rules are retrieved from Rulezet.

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GHSA-H7C8-WRGV-C7F2

CVE-2026-63804 (GCVE-0-2026-63804)

Tags

Sightings

Nomenclature