GHSA-623Q-H292-Q6FF
Vulnerability from github – Published: 2026-08-15 15:30 – Updated: 2026-08-17 06:33In 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() do_zone_finish() btrfs_inc_block_group_ro() btrfs_wait_for_commit()
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.
{
"affected": [],
"aliases": [
"CVE-2026-74572"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T13:18:02Z",
"severity": "HIGH"
},
"details": "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.",
"id": "GHSA-623q-h292-q6ff",
"modified": "2026-08-17T06:33:54Z",
"published": "2026-08-15T15:30:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74572"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1ebe51c29fa9755d5b2fea28727c051117907cf8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/75859a7cd77cd2ddaddbcb963e3fcd34738953af"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c3320873e0c04ce7b746fc8fe948f07bbbbdec33"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/deddd28fd83c264ee2ff5cd6b34449a9f1be6112"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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