FKIE_CVE-2025-71159

Vulnerability from fkie_nvd - Published: 2026-01-23 16:15 - Updated: 2026-01-26 15:03
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node() Previously, btrfs_get_or_create_delayed_node() set the delayed_node's refcount before acquiring the root->delayed_nodes lock. Commit e8513c012de7 ("btrfs: implement ref_tracker for delayed_nodes") moved refcount_set inside the critical section, which means there is no longer a memory barrier between setting the refcount and setting btrfs_inode->delayed_node. Without that barrier, the stores to node->refs and btrfs_inode->delayed_node may become visible out of order. Another thread can then read btrfs_inode->delayed_node and attempt to increment a refcount that hasn't been set yet, leading to a refcounting bug and a use-after-free warning. The fix is to move refcount_set back to where it was to take advantage of the implicit memory barrier provided by lock acquisition. Because the allocations now happen outside of the lock's critical section, they can use GFP_NOFS instead of GFP_ATOMIC.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/83f59076a1ae6f5c6845d6f7ed3a1a373d883684
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c8385851a5435f4006281828d428e5d0b0bbf8af
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()\n\nPreviously, btrfs_get_or_create_delayed_node() set the delayed_node\u0027s\nrefcount before acquiring the root-\u003edelayed_nodes lock.\nCommit e8513c012de7 (\"btrfs: implement ref_tracker for delayed_nodes\")\nmoved refcount_set inside the critical section, which means there is\nno longer a memory barrier between setting the refcount and setting\nbtrfs_inode-\u003edelayed_node.\n\nWithout that barrier, the stores to node-\u003erefs and\nbtrfs_inode-\u003edelayed_node may become visible out of order. Another\nthread can then read btrfs_inode-\u003edelayed_node and attempt to\nincrement a refcount that hasn\u0027t been set yet, leading to a\nrefcounting bug and a use-after-free warning.\n\nThe fix is to move refcount_set back to where it was to take\nadvantage of the implicit memory barrier provided by lock\nacquisition.\n\nBecause the allocations now happen outside of the lock\u0027s critical\nsection, they can use GFP_NOFS instead of GFP_ATOMIC."
    }
  ],
  "id": "CVE-2025-71159",
  "lastModified": "2026-01-26T15:03:51.687",
  "metrics": {},
  "published": "2026-01-23T16:15:52.793",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/83f59076a1ae6f5c6845d6f7ed3a1a373d883684"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c8385851a5435f4006281828d428e5d0b0bbf8af"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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