CVE-2026-74572 (GCVE-0-2026-74572)
Vulnerability from cvelistv5
Published
2026-08-15 12:28
Modified
2026-08-17 05:48
Severity ?
VLAI Severity ?
EPSS score ?
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 Version: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 Version: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 Version: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 Version: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 Version: fca3a1cd3ba47f1815e0c0fcdc9aafaf02ee0a75 Version: 6.5.5 ≤ |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/btrfs/zoned.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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{
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},
{
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"versionType": "git"
},
{
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"version": "13bb483d32abb6f8ebd40141d87eb68f11cc2dd2",
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{
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"status": "affected",
"version": "6.5.5",
"versionType": "semver"
}
]
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{
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"product": "Linux",
"programFiles": [
"fs/btrfs/zoned.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.6"
},
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"status": "unaffected",
"version": "0",
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},
{
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"status": "unaffected",
"version": "6.6.151",
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},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.103",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.44",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.151",
"versionStartIncluding": "6.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.103",
"versionStartIncluding": "6.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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},
{
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"versionStartIncluding": "6.5.5",
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:48:51.651Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd"
},
{
"url": "https://git.kernel.org/stable/c/c3320873e0c04ce7b746fc8fe948f07bbbbdec33"
},
{
"url": "https://git.kernel.org/stable/c/deddd28fd83c264ee2ff5cd6b34449a9f1be6112"
},
{
"url": "https://git.kernel.org/stable/c/75859a7cd77cd2ddaddbcb963e3fcd34738953af"
},
{
"url": "https://git.kernel.org/stable/c/1ebe51c29fa9755d5b2fea28727c051117907cf8"
}
],
"title": "btrfs: zoned: fix deadlock between metadata writeback and transaction commit",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74572",
"datePublished": "2026-08-15T12:28:11.328Z",
"dateReserved": "2026-08-15T05:44:03.917Z",
"dateUpdated": "2026-08-17T05:48:51.651Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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