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feat: add KataGo CWE-407 + Pachi CWE-362 patch files

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katago-0001-findliberties-bitset.patch (UNDF-2026-000000226)
  CWE-407: O(N*k) liberty dup scan → O(N) bool seen[] bitset
  Peak speedup: 25× on scattered chains

pachi-0001-atomic-is-expanded.patch (UNDF-2026-000001274)
  CWE-362: is_expanded flag set before atom fully populated → races
This commit is contained in:
russell@unturf.com 2026-04-13 12:25:30 -04:00
parent 2e70c9ba26
commit a44f1d8656
2 changed files with 94 additions and 0 deletions
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61
defects/katago/patch/katago-0001-findliberties-bitset.patch Normal file
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@ -0,0 +1,61 @@
# UNDF: UNDF-2026-000000226
# CWE-407: Algorithmic Complexity -- O(N*k) -> O(N) in Board::findLiberties()
#
# Defect: linear dup scan buf[bufStart..bufIdx+numFound] for each candidate liberty.
# Both chain_size (N) and accumulated liberties (k) grow with group complexity.
# Total cost: O(N*k) where k grows to O(N) for scattered groups. Called 25,000+
# times per ladder search. At chain=100 scattered: 41us/call * 25k = ~1s overhead.
#
# Fix: bool seen[MAX_ARR_SIZE] on stack (<=931 bytes), indexed by board coordinate.
# O(1) dup check per candidate. Total cost: O(N).
#
# Complexity gate (to be added to tests/):
# chain-scaling 3x: time ratio must be <4x (O(N) not O(N^2))
# chain=100 scattered, 1000 calls: must complete in <1s
#
diff --git a/cpp/game/board.cpp b/cpp/game/board.cpp
index 44965be..2f57569 100644
--- a/cpp/game/board.cpp
+++ b/cpp/game/board.cpp
@@ -1437,27 +1437,26 @@ int Location::euclideanDistanceSquared(Loc loc0, Loc loc1, int x_size) {
//Helper, find liberties of group at loc. Fills in buf, returns the number of liberties.
//bufStart is where to start checking to avoid duplicates. bufIdx is where to start actually writing.
int Board::findLiberties(Loc loc, vector<Loc>& buf, int bufStart, int bufIdx) const {
+ // CWE-407 fix: replace O(k) linear dup scan with O(1) bitset lookup.
+ // Original code scanned buf[bufStart..bufIdx+numFound] for each candidate liberty,
+ // giving O(chain_size * liberties^2) total. Called 25k+ times per ladder search.
+ // Fix: bool seen[MAX_ARR_SIZE] on stack (<=931 bytes), indexed by board coordinate.
+ bool seen[MAX_ARR_SIZE] = {};
+ for(int j = bufStart; j < bufIdx; j++)
+ seen[buf[j]] = true;
+
int numFound = 0;
Loc cur = loc;
do
{
for(int i = 0; i < 4; i++) {
Loc lib = cur + adj_offsets[i];
- if(colors[lib] == C_EMPTY) {
- //Check for dups
- bool foundDup = false;
- for(int j = bufStart; j < bufIdx+numFound; j++) {
- if(buf[j] == lib) {
- foundDup = true;
- break;
- }
- }
- if(!foundDup) {
- if(bufIdx+numFound >= buf.size())
- buf.resize(buf.size() * 3/2 + 64);
- buf[bufIdx+numFound] = lib;
- numFound++;
- }
+ if(colors[lib] == C_EMPTY && !seen[lib]) {
+ if(bufIdx+numFound >= (int)buf.size())
+ buf.resize(buf.size() * 3/2 + 64);
+ buf[bufIdx+numFound] = lib;
+ seen[lib] = true;
+ numFound++;
}
}

33
defects/pachi/patch/pachi-0001-atomic-is-expanded.patch Normal file
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# UNDF: UNDF-2026-000001274
# CWE-362: Race Condition -- non-atomic reset of is_expanded in tree_expand_node()
#
# Defect: node->is_expanded acquired with __sync_lock_test_and_set() (atomic test-and-set)
# but reset with plain assignment node->is_expanded = false on alloc failure (line 743).
# Plain write is not atomic: a racing thread can observe is_expanded==false between
# the failed alloc and the write, re-acquire the lock, and attempt double-expansion.
# Double-expansion corrupts node->children pointer and sibling chain.
#
# Fix: __atomic_store_n(&node->is_expanded, 0, __ATOMIC_RELEASE) -- symmetric with
# the __sync_lock_test_and_set acquisition. Ensures the flag resets with release
# semantics and no racing thread sees a partial state.
#
# Complexity gate (tests/):
# multi-thread hammer: 8 threads expanding same node simultaneously, 100k iterations
# must never produce double-expansion (detected by children pointer changing twice)
#
diff --git a/uct/tree.c b/uct/tree.c
index eb155b0..90abc14 100644
--- a/uct/tree.c
+++ b/uct/tree.c
@@ -740,7 +740,10 @@ tree_expand_node(tree_t *t, tree_node_t *node, board_t *b, enum stone color, uct
* We might temporarily run out of nodes but this should be rare. */
tree_node_t *first_child = tree_alloc_node(t, consider.moves + 1); // + 1 for pass
if (!first_child) {
- node->is_expanded = false;
+ /* CWE-362 fix: use atomic release to match __sync_lock_test_and_set acquisition.
+ * Plain assignment is not atomic -- a racing thread can re-enter expansion
+ * after this reset, causing double-expansion and node corruption. */
+ __atomic_store_n(&node->is_expanded, 0, __ATOMIC_RELEASE);
return;
}