CVE-2026-74572 - btrfs: zoned: fix deadlock between metadata writeback and transaction commit

CVE-2026-74572 - btrfs: zoned: fix deadlock between metadata writeback and transaction commit

https://cvefeed.io/rssfeed/latest.atom / Sat, 08/15/2026 - 16:26
CVE ID :CVE-2026-74572
Published : Aug. 15, 2026, 1:18 p.m. | 11 minutes ago
Description :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() 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.
Severity: 0.0 | NA
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