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CVE-2026-74572 (GCVE-0-2026-74572)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:28 – Updated: 2026-08-17 05:48
VLAI
Title
btrfs: zoned: fix deadlock between metadata writeback and transaction commit
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: zoned: fix deadlock between metadata writeback and transaction commit When writing out metadata extent buffers in a zoned filesystem, btree_writepages() holds fs_info->zoned_meta_io_lock across the whole writeback loop, including the call to btrfs_check_meta_write_pointer() -> check_bg_is_active(). For the tree-log block group, check_bg_is_active() may fail to activate the zone and fall back to btrfs_zone_finish_one_bg() to free an active zone. That path waits for the running transaction to commit while still holding zoned_meta_io_lock, but the committer needs that same lock to write out the tree extents, so the two tasks deadlock: Task A (kworker, metadata writeback) Task B (fsstress, transaction commit) ------------------------------------ ------------------------------------- wb_workfn() btrfs_commit_transaction(T) btree_writepages() btrfs_write_and_wait_transaction() btrfs_zoned_meta_io_lock() btrfs_write_marked_extents() btrfs_check_meta_write_pointer() btree_writepages() check_bg_is_active() [treelog_bg] btrfs_zoned_meta_io_lock() btrfs_zone_finish_one_bg() <blocks on zoned_meta_io_lock, btrfs_zone_finish() held by Task A> do_zone_finish() btrfs_inc_block_group_ro() btrfs_wait_for_commit() <blocks waiting for commit of transaction T, done by Task B> The sibling branch in check_bg_is_active() already drops zoned_meta_io_lock around do_zone_finish() for this exact reason. Do the same in the tree-log branch: release the lock around btrfs_zone_finish_one_bg() and re-acquire it afterwards. The lock only protects fs_info->active_{meta,system}_bg, which this branch does not touch, and ctx->zoned_bg keeps a reference to the block group across the unlock, so nothing is lost while the lock is dropped. This hang occasionally reproduces with fstests generic/475 on a zoned btrfs filesystem.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 , < 18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd (git)
Affected: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 , < c3320873e0c04ce7b746fc8fe948f07bbbbdec33 (git)
Affected: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 , < deddd28fd83c264ee2ff5cd6b34449a9f1be6112 (git)
Affected: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 , < 75859a7cd77cd2ddaddbcb963e3fcd34738953af (git)
Affected: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 , < 1ebe51c29fa9755d5b2fea28727c051117907cf8 (git)
Affected: fca3a1cd3ba47f1815e0c0fcdc9aafaf02ee0a75 (git)
Affected: 6.5.5 , < 6.6 (semver)
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Linux Linux Affected: 6.6
Unaffected: 0 , < 6.6 (semver)
Unaffected: 6.6.151 , ≤ 6.6.* (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zoned: fix deadlock between metadata writeback and transaction commit\n\nWhen writing out metadata extent buffers in a zoned filesystem,\nbtree_writepages() holds fs_info-\u003ezoned_meta_io_lock across the whole\nwriteback loop, including the call to btrfs_check_meta_write_pointer() -\u003e\ncheck_bg_is_active().\n\nFor the tree-log block group, check_bg_is_active() may fail to activate\nthe zone and fall back to btrfs_zone_finish_one_bg() to free an active\nzone. That path waits for the running transaction to commit while still\nholding zoned_meta_io_lock, but the committer needs that same lock to\nwrite out the tree extents, so the two tasks deadlock:\n\n  Task A (kworker, metadata writeback)      Task B (fsstress, transaction commit)\n  ------------------------------------      -------------------------------------\n  wb_workfn()                               btrfs_commit_transaction(T)\n   btree_writepages()                        btrfs_write_and_wait_transaction()\n    btrfs_zoned_meta_io_lock()                btrfs_write_marked_extents()\n    btrfs_check_meta_write_pointer()           btree_writepages()\n     check_bg_is_active() [treelog_bg]          btrfs_zoned_meta_io_lock()\n      btrfs_zone_finish_one_bg()               \u003cblocks on zoned_meta_io_lock,\n       btrfs_zone_finish()                      held by Task A\u003e\n        do_zone_finish()\n         btrfs_inc_block_group_ro()\n          btrfs_wait_for_commit()\n           \u003cblocks waiting for commit\n            of transaction T, done by\n            Task B\u003e\n\nThe sibling branch in check_bg_is_active() already drops zoned_meta_io_lock\naround do_zone_finish() for this exact reason. Do the same in the tree-log\nbranch: release the lock around btrfs_zone_finish_one_bg() and re-acquire\nit afterwards. The lock only protects fs_info-\u003eactive_{meta,system}_bg,\nwhich this branch does not touch, and ctx-\u003ezoned_bg keeps a reference to\nthe block group across the unlock, so nothing is lost while the lock\nis dropped.\n\nThis hang occasionally reproduces with fstests generic/475 on a zoned\nbtrfs filesystem."
        }
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              "value": "AV:N - On storage servers exporting a zoned btrfs volume via nfsd or ksmbd, remote client write/fsync I/O reaches btrfs_commit_transaction() and btree_writepages() on the server kernel without any local syscall access.\nAC:L - The attacker controls both deadlock participants by driving concurrent metadata dirtying/writeback and transaction commits (reproduced with fsstress/fstests generic/475); the kworker writeback side is a direct result of attacker-generated btree dirty pages.\nPR:N - Exploitation requires only network write access to an NFS or SMB export of the zoned btrfs filesystem; no local account, capability, or init-namespace privilege is needed when the export permits client writes.\nUI:N - The deadlock is triggered entirely by the attacker\u0027s own concurrent write and sync I/O; no victim must mount a filesystem, open a file, or perform any interactive action.\nS:U - The mutex deadlock freezes btrfs metadata I/O within the same host kernel security authority; it does not cross a VM, IOMMU, or sandbox boundary.\nC:N - This is a lock-ordering deadlock with no memory corruption, out-of-bounds access, use-after-free, or information disclosure of any kind.\nI:N - The bug causes tasks to block indefinitely on locks but does not corrupt, modify, or overwrite any data or enable arbitrary writes or code execution.\nA:H - The circular wait between zoned_meta_io_lock and btrfs_wait_for_commit() permanently hangs metadata writeback and transaction commit, freezing all I/O on the affected zoned btrfs filesystem."
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That path waits for the running transaction to commit while still\\nholding zoned_meta_io_lock, but the committer needs that same lock to\\nwrite out the tree extents, so the two tasks deadlock:\\n\\n  Task A (kworker, metadata writeback)      Task B (fsstress, transaction commit)\\n  ------------------------------------      -------------------------------------\\n  wb_workfn()                               btrfs_commit_transaction(T)\\n   btree_writepages()                        btrfs_write_and_wait_transaction()\\n    btrfs_zoned_meta_io_lock()                btrfs_write_marked_extents()\\n    btrfs_check_meta_write_pointer()           btree_writepages()\\n     check_bg_is_active() [treelog_bg]          btrfs_zoned_meta_io_lock()\\n      btrfs_zone_finish_one_bg()               \u003cblocks on zoned_meta_io_lock,\\n       btrfs_zone_finish()                      held by Task A\u003e\\n        do_zone_finish()\\n         btrfs_inc_block_group_ro()\\n          btrfs_wait_for_commit()\\n           \u003cblocks waiting for commit\\n            of transaction T, done by\\n            Task B\u003e\\n\\nThe sibling branch in check_bg_is_active() already drops zoned_meta_io_lock\\naround do_zone_finish() for this exact reason. Do the same in the tree-log\\nbranch: release the lock around btrfs_zone_finish_one_bg() and re-acquire\\nit afterwards. The lock only protects fs_info-\u003eactive_{meta,system}_bg,\\nwhich this branch does not touch, and ctx-\u003ezoned_bg keeps a reference to\\nthe block group across the unlock, so nothing is lost while the lock\\nis dropped.\\n\\nThis hang occasionally reproduces with fstests generic/475 on a zoned\\nbtrfs filesystem.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/btrfs/zoned.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2\",\"lessThan\":\"18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2\",\"lessThan\":\"c3320873e0c04ce7b746fc8fe948f07bbbbdec33\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2\",\"lessThan\":\"deddd28fd83c264ee2ff5cd6b34449a9f1be6112\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2\",\"lessThan\":\"75859a7cd77cd2ddaddbcb963e3fcd34738953af\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2\",\"lessThan\":\"1ebe51c29fa9755d5b2fea28727c051117907cf8\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fca3a1cd3ba47f1815e0c0fcdc9aafaf02ee0a75\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6.5.5\",\"lessThan\":\"6.6\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/btrfs/zoned.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.6\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.6\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.151\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.103\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.44\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.8\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/1ebe51c29fa9755d5b2fea28727c051117907cf8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/75859a7cd77cd2ddaddbcb963e3fcd34738953af\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c3320873e0c04ce7b746fc8fe948f07bbbbdec33\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/deddd28fd83c264ee2ff5cd6b34449a9f1be6112\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-21T10:11:29+00:00",
      "cve": "CVE-2026-74572",
      "id": "CVE-2026-74572",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: btrfs: zoned: fix deadlock between metadata writeback and transaction commit",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74572.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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