btrfs: zoned: fix deadlock between metadata writeback and transaction commit
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.6, 6.6.151, 6.12.103, 6.18.44, 7.1.8
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: yes
- Technical impact: partial
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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- Linux Linux
From 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 · fixed in 18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd; From 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 · fixed in c3320873e0c04ce7b746fc8fe948f07bbbbdec33; From 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 · fixed in deddd28fd83c264ee2ff5cd6b34449a9f1be6112; From 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 · fixed in 75859a7cd77cd2ddaddbcb963e3fcd34738953af; From 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 · fixed in 1ebe51c29fa9755d5b2fea28727c051117907cf8; From 6.5.5 · fixed in 6.6
- Linux Linux
6.6
- KernelLinux
From 6.6.0 · fixed in 6.6.151; From 6.7.0 · fixed in 6.12.103; From 6.13.0 · fixed in 6.18.44; From 6.19.0 · fixed in 7.1.8