HighFix available

btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs() In the beginning of the loop, we try to obtain a locked delayed ref head, if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), which can return an error pointer. If the error pointer is -EAGAIN we do a continue and go back to the beginning of the loop, which will not try again to call btrfs_select_ref_head() since 'locked_ref' is no longer NULL but it's ERR_PTR(-EAGAIN), and then we do: spin_lock(&locked_ref->lock); against a ERR_PTR(-EAGAIN) value, generating an invalid pointer dereference. Fix this by ensuring that 'locked_ref' is set to NULL when btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' as well, to prevent infinite looping. We do this by doing a goto to the bottom of the loop that already sets 'locked_ref' to NULL and does a cond_resched(), with an increment to 'count' right before the goto. These measures were in place before the refactoring in commit 0110a4c43451 ("btrfs: refactor __btrfs_run_delayed_refs loop") but were unintentionally lost afterwards.

Products: Kernel
Affected versions: Not specified
Fixed versions: 5.10.261, 5.15.212, 6.1.178, 6.12.97, 6.18.40, 6.6.145, 7.1.5
CVEs: CVE-2026-74321
Confirmed fixed CVEs: Not specified
Updated in this feed: 4 Nov 2026, 21:31 UTC · Revision 1

Source evidence

btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()

core-osv · Original source

Published 15 Aug 2026, 05:58 UTC

osv:CVE-2026-74321

Kernel

Fixed versions: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5

Complete source record

{
  "id": "7cc9483e03576185a3d0d539216c0816988654e222220fe62333c2a9ab0b763b",
  "url": "https://osv.dev/vulnerability/CVE-2026-74321",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs() In the beginning of the loop, we try to obtain a locked delayed ref head, if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), which can return an error pointer. If the error pointer is -EAGAIN we do a continue and go back to the beginning of the loop, which will not try again to call btrfs_select_ref_head() since 'locked_ref' is no longer NULL but it's ERR_PTR(-EAGAIN), and then we do: spin_lock(&locked_ref->lock); against a ERR_PTR(-EAGAIN) value, generating an invalid pointer dereference. Fix this by ensuring that 'locked_ref' is set to NULL when btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' as well, to prevent infinite looping. We do this by doing a goto to the bottom of the loop that already sets 'locked_ref' to NULL and does a cond_resched(), with an increment to 'count' right before the goto. These measures were in place before the refactoring in commit 0110a4c43451 (\"btrfs: refactor __btrfs_run_delayed_refs loop\") but were unintentionally lost afterwards.",
    "evidence": "osv:CVE-2026-74321",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
        "fixed_versions": [
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          {
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            "evidence": "/affected/1/ranges"
          }
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        "affected_versions": []
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    "severity": "high",
    "structured": {
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      ],
      "modified": "2026-10-28T02:30:39.827001391Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/015dc4a1e0c2cba551d4620eba13d26d5081dc34",
        "https://git.kernel.org/stable/c/3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1",
        "https://git.kernel.org/stable/c/486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae",
        "https://git.kernel.org/stable/c/65770111a2d47c2b15e20b2ba92bb12198f289d4",
        "https://git.kernel.org/stable/c/9faa6b69ad73f03c7bde53e07d75a28822dc9a1a",
        "https://git.kernel.org/stable/c/a71143590ce9764dbcb47617647592ff8b4d48bc",
        "https://git.kernel.org/stable/c/ba9fa2ff5981589bb49094d3358c339b37c47f53",
        "https://git.kernel.org/stable/c/c372ca227e16bace86f1df1fa4ae6849e2fcfa28",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74321.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74321",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74321.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-74321",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
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  "source_id": "core-osv",
  "document_id": 507328,
  "published_at": "2026-08-15T05:58:17.485+00:00"
}