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triedb/pathdb: fix lookup sentinel collision with zero disk layer root

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lookup.accountTip and storageTip used common.Hash{} as the "state is
stale" sentinel while ALSO returning common.Hash{} when the disk layer
itself happened to be keyed by the zero hash. lookupAccount/Storage
then blindly compared the returned value against common.Hash{} and
misreported a legitimate disk-layer fallback as errSnapshotStale.

For a merkle path database this sentinel collision is invisible: an
empty merkle trie hashes to types.EmptyRootHash which is a concrete
non-zero keccak, so the disk layer's root never equals common.Hash{}.
The collision only shows up once the disk layer root can legitimately
be zero — for example, a fresh verkle/bintrie database where the empty
binary trie hashes to EmptyVerkleHash = common.Hash{}. In that
configuration, any Account/Storage lookup for a key that has never
been written ends up taking the disk-layer fallback branch, which
correctly returns base=common.Hash{}, which lookupAccount then
misreads as "stale" and bubbles an error up to the caller.

Fix: change accountTip/storageTip to return (common.Hash, bool) so the
"found the tip" signal is carried out of band from the hash value.
lookupAccount/Storage now consult the boolean rather than comparing
the returned hash to zero. The returned hash itself may still be zero
(that is a valid disk-layer root on the bintrie path) and callers
must not treat it as a sentinel.

Noticed while wiring the bintrie flat-state reader in a separate
branch; the fix is scheme-agnostic and lands here so it can flow into
master independently of that work.
This commit is contained in:
CPerezz 2026-04-08 00:17:55 +02:00
parent 04e40995d9
commit 0d16a41887
No known key found for this signature in database
GPG key ID: 62045F34B97177DD
2 changed files with 22 additions and 23 deletions
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8
triedb/pathdb/layertree.go
View file

@ -319,8 +319,8 @@ func (tree *layerTree) lookupAccount(accountHash common.Hash, state common.Hash)
tree.lock.RLock()
defer tree.lock.RUnlock()
tip := tree.lookup.accountTip(accountHash, state, tree.base.root)
if tip == (common.Hash{}) {
tip, ok := tree.lookup.accountTip(accountHash, state, tree.base.root)
if !ok {
return nil, fmt.Errorf("[%#x] %w", state, errSnapshotStale)
}
l := tree.layers[tip]
@ -337,8 +337,8 @@ func (tree *layerTree) lookupStorage(accountHash common.Hash, slotHash common.Ha
tree.lock.RLock()
defer tree.lock.RUnlock()
tip := tree.lookup.storageTip(accountHash, slotHash, state, tree.base.root)
if tip == (common.Hash{}) {
tip, ok := tree.lookup.storageTip(accountHash, slotHash, state, tree.base.root)
if !ok {
return nil, fmt.Errorf("[%#x] %w", state, errSnapshotStale)
}
l := tree.layers[tip]

37
triedb/pathdb/lookup.go
View file

@ -92,12 +92,16 @@ func newLookup(head layer, descendant func(state common.Hash, ancestor common.Ha
// stateID or is a descendant of it.
//
// If found, the account data corresponding to the supplied stateID resides
// in that layer. Otherwise, two scenarios are possible:
// in the layer identified by the returned hash (ok=true). Otherwise,
// (common.Hash{}, false) is returned to signal that the supplied stateID is
// stale.
//
// (a) the account remains unmodified from the current disk layer up to the state
// layer specified by the stateID: fallback to the disk layer for data retrieval,
// (b) or the layer specified by the stateID is stale: reject the data retrieval.
func (l *lookup) accountTip(accountHash common.Hash, stateID common.Hash, base common.Hash) common.Hash {
// Note the returned hash may itself be common.Hash{} when the disk layer's
// root is zero — as is the case for a fresh verkle/bintrie database whose
// empty trie hashes to EmptyVerkleHash. Callers must therefore consult the
// boolean rather than comparing the returned hash against common.Hash{}
// directly.
func (l *lookup) accountTip(accountHash common.Hash, stateID common.Hash, base common.Hash) (common.Hash, bool) {
// Traverse the mutation history from latest to oldest one. Several
// scenarios are possible:
//
@ -123,31 +127,26 @@ func (l *lookup) accountTip(accountHash common.Hash, stateID common.Hash, base c
// containing the modified data. Otherwise, the current state may be ahead
// of the requested one or belong to a different branch.
if list[i] == stateID || l.descendant(stateID, list[i]) {
return list[i]
return list[i], true
}
}
// No layer matching the stateID or its descendants was found. Use the
// current disk layer as a fallback.
if base == stateID || l.descendant(stateID, base) {
return base
return base, true
}
// The layer associated with 'stateID' is not the descendant of the current
// disk layer, it's already stale, return nothing.
return common.Hash{}
return common.Hash{}, false
}
// storageTip traverses the layer list associated with the given account and
// slot hash in reverse order to locate the first entry that either matches
// the specified stateID or is a descendant of it.
//
// If found, the storage data corresponding to the supplied stateID resides
// in that layer. Otherwise, two scenarios are possible:
//
// (a) the storage slot remains unmodified from the current disk layer up to
// the state layer specified by the stateID: fallback to the disk layer for
// data retrieval, (b) or the layer specified by the stateID is stale: reject
// the data retrieval.
func (l *lookup) storageTip(accountHash common.Hash, slotHash common.Hash, stateID common.Hash, base common.Hash) common.Hash {
// See accountTip for the returned-hash / ok convention — the same
// bintrie-zero-root caveat applies here.
func (l *lookup) storageTip(accountHash common.Hash, slotHash common.Hash, stateID common.Hash, base common.Hash) (common.Hash, bool) {
list := l.storages[storageKey(accountHash, slotHash)]
for i := len(list) - 1; i >= 0; i-- {
// If the current state matches the stateID, or the requested state is a
@ -155,17 +154,17 @@ func (l *lookup) storageTip(accountHash common.Hash, slotHash common.Hash, state
// containing the modified data. Otherwise, the current state may be ahead
// of the requested one or belong to a different branch.
if list[i] == stateID || l.descendant(stateID, list[i]) {
return list[i]
return list[i], true
}
}
// No layer matching the stateID or its descendants was found. Use the
// current disk layer as a fallback.
if base == stateID || l.descendant(stateID, base) {
return base
return base, true
}
// The layer associated with 'stateID' is not the descendant of the current
// disk layer, it's already stale, return nothing.
return common.Hash{}
return common.Hash{}, false
}
// addLayer traverses the state data retained in the specified diff layer and