Post-merge follow-up to #71770. Both defects were found by @helix4u in review
and reproduced against merged main before fixing.
1. Check/use race in _copy_source_bundle (my bug, from the #71770 follow-up
commit). It called has_live_connection(), released the registry lock, and
only then ran shutil.copy2() over the bundle. A tracked connection could
open in that window; the copy's close() then cancels its POSIX advisory
locks -- the exact class #71724 closed. Measured on main: a racer thread
opened a connection mid-copy after blocking 0.000s.
Adds sqlite_safe_read.offline_file_access(), a context manager that holds
the connection-lifecycle lock across an entire multi-step raw access, and
routes the bundle copy through it. Same racer now blocks 10.0s until every
raw descriptor is closed. Any future raw read of a database file (hashing,
moving a bundle aside) should use this rather than a bare pre-check.
2. _copy_state_meta_salvage assumed a 'key' column. A damaged state_meta can
keep 'value' and lose 'key'; columns.index("key") then raised ValueError
and aborted the whole partial recovery. The mirror case (key without
value) would have copied key-only rows and reported the table complete.
Now requires both, matching the non-partial _copy_state_meta, so an
unusable optional table is recorded as missing/failed and --allow-partial
still recovers sessions and messages.
Both regression tests verified by sabotage: reinstating the bare pre-check
fails the race test, removing the key/value requirement fails the other.
937 targeted tests green.
Addresses review findings on the previous commits. Three of them were real
defects I reproduced against my own head before fixing.
1. Check/use race (BLOCKING). read_header_bytes_preopen() checked
has_live_connection() under _live_lock, released it, then did the raw
open/read/close outside the lock; connect_tracked() opened before
registering. A thread could pass the "nothing is live" check, another
could open a connection and BEGIN IMMEDIATE, and the first thread's
close() then cancelled its POSIX locks -- the exact bug this guard
exists to prevent. Reproduced deterministically (BLOCKED -> ACQUIRED).
_live_lock now spans all three lifecycle transitions: open+register,
unregister+close, and check+open+read+close.
2. Read-only connections keyed by URI spelling (BLOCKING). SessionDB's
read-only path opens file:/…/state.db?mode=ro; that string was fed to
Path.resolve(), producing <cwd>/file:/…/state.db?mode=ro. No probe of
the real Path could match, so read-only connections were invisible to
the guard and their locks cancellable. Reproduced with no forced
scheduling. Keys now come from PRAGMA database_list (canonical path),
with an explicit tracking_path override.
3. Fail-open wrapper (HIGH). _connect_tracked_db() caught every exception
and retried an untracked plain connect, so any error silently disabled
the guard. Now only ImportError (scaffold installs without hermes_cli)
falls back; real failures propagate.
4. Backup paths that warned and proceeded (MEDIUM). _backup_corrupt_db()
and _backup_db_file() raw-read live databases; they now REFUSE when a
connection is live rather than warning. Losing a forensic copy beats
corrupting the database being rescued.
Custom factories are no longer rejected (that broke legitimate callers) nor
silently untracked -- the tracking close() is mixed into whatever factory is
in play, including when an opener substitutes its own after the fact.
WAL POLICY: #70055 is RESTORED, not reverted. My earlier justification was
confounded -- the clean WAL result came from 3.53.1, which carries both the
WAL-reset fix AND 3.51.0's broken-lock defenses, so it said nothing about the
bundled 3.50.4. Re-measured on 3.50.4 with the lock fix in place: WAL 0/3 and
DELETE 0/3, i.e. no evidence WAL is safer. Upstream still documents the
WAL-reset bug through 3.51.2 as serious. Keeping new databases out of WAL
until a fixed runtime ships is the conservative call, and the WAL policy does
not belong in this root-cause fix.
Six sabotage runs confirm each new test fails when its defect is reinstated
(including two that initially did NOT -- the race test was rewritten to pause
inside the byte read, and a separate test added for the opener-substituted
factory path). 1124 targeted tests green.
Completeness pass over the previous commit.
Registry leak (would have silently disabled the guard): the first version
incremented on open but decremented only in SessionDB.close(). kanban's
connect() hands raw connections to callers who close them directly (4 sites),
so its counter only ever went up — after enough kanban operations every
byte-probe on that path would be refused forever, disabling zeroed-file and
header detection. Replaced manual track/untrack with a TrackedConnection
subclass that untracks in close(), the one method every close path goes
through. Verified across plain close, contextlib.closing, double close,
nested lifetimes, and 100-cycle churn; `with conn:` (a transaction scope, not
a close) correctly stays tracked.
Also: a caller-supplied factory now wins instead of raising TypeError on a
duplicate kwarg, since tracking is an optimisation for the probe guard, not a
precondition for opening the database.
Removed _apply_delete_for_wal_reset_bug, dead after the force-DELETE revert.
Audit notes:
- DELETE mode is still reachable via the NFS/SMB/FUSE fallback and remains
correct there; those users are protected by the raw-read fix, not by the
journal mode.
- The remaining whole-file reads are on genuinely offline artifacts:
_backup_db_file (DB won't open; bytes preserved for forensics),
_backup_corrupt_db (quarantine path, now warns if a connection is live),
and backup verification of snapshots. backup._safe_copy_db already uses
the SQLite backup API rather than a byte copy.
- The mechanism is POSIX-specific (Windows byte-range locks are handle-scoped,
not process-scoped), so this is a Linux/macOS correctness fix; the change is
platform-neutral and safe on Windows.
Sibling tests updated: session recovery no longer expects a DELETE-mode
recovered DB, and the kanban WAL-fallback test patches the connect site that
actually runs now.
`hermes sessions optimize` could corrupt state.db. Root cause is Hermes,
not the SQLite WAL-reset bug (#69784).
close() on ANY file descriptor for a SQLite database cancels every POSIX
advisory lock the process holds on that file, including a running VACUUM's
EXCLUSIVE lock (sqlite.org/howtocorrupt.html section 2.2). Hermes byte-probed
live databases in several hot paths: the zeroed-state.db detector runs on every
SessionDB construction (and the gateway builds those constantly), and kanban's
post-commit invariant check ran after every COMMIT. While VACUUM rewrote the
file, those probes dropped its lock and let other processes write into it.
A/B against the real code, only variable being the raw read:
SQLite 3.50.4, VACUUM + concurrent writers, DELETE mode
raw open/close during VACUUM 8 vacuums, 319 vacuum errors, 2/2 corrupt
no raw read (control) 229 vacuums, 0 vacuum errors, 0/2 corrupt
SQLite 3.53.1 (WAL-reset FIXED) reproduces identically: 2/2 corrupt.
After this change: 0/4 corrupt, 0 vacuum errors.
Because the upgraded runtime corrupts too, replacing the embedded SQLite does
not fix this class; and because DELETE is where it reproduces, #70055's
"force DELETE on vulnerable builds" mitigation steered users into the failing
mode. That gate is reverted here: vulnerable builds get WAL again and still
warn so operators can upgrade.
- add hermes_cli/sqlite_safe_read.py: read page_count via PRAGMA over the
existing connection instead of open()+seek(28); byte-level probes are
restricted to before any connection exists and refused once one is live,
with an explicit force= escape for offline artifacts (snapshots, archives)
- track live connections in SessionDB and kanban's connect so that guard is
enforced rather than merely documented
- kanban's torn-extend check now only applies under a rollback journal; in WAL
a committed page may still legitimately sit in the -wal file
- revert the force-DELETE WAL gate and update the tests that pinned it
Regression tests assert the behavioural contract (an external process stays
locked out across Hermes' inspection calls) and were verified to fail when the
old raw-open behaviour is restored.
