Add sentinels to index format enums.

faiss/MetricType.h

@@ -24,14 +24,15 @@ namespace faiss {
 /// (brute-force) indices supporting additional metric types for vector
 /// comparison.
 ///
-/// NOTE: when adding or removing values, update metric_type_from_int() below.
+/// NOTE: when adding or removing values, update metric_type_from_int()
+///       and metric_type_count() below.
 enum MetricType {
-    METRIC_INNER_PRODUCT = 0, ///< maximum inner product search
-    METRIC_L2 = 1,            ///< squared L2 search
-    METRIC_L1,                ///< L1 (aka cityblock)
-    METRIC_Linf,              ///< infinity distance
-    METRIC_Lp,                ///< L_p distance, p is given by a faiss::Index
-                              /// metric_arg
+    METRIC_INNER_PRODUCT, ///< maximum inner product search
+    METRIC_L2,            ///< squared L2 search
+    METRIC_L1,            ///< L1 (aka cityblock)
+    METRIC_Linf,          ///< infinity distance
+    METRIC_Lp,            ///< L_p distance, p is given by a faiss::Index
+                          /// metric_arg
 
     /// some additional metrics defined in scipy.spatial.distance
     METRIC_Canberra = 20,
@@ -68,6 +69,12 @@ inline MetricType metric_type_from_int(int x) {
     return static_cast<MetricType>(x);
 }
 
+/// Count of entries in the MetricType enum.
+constexpr size_t metric_type_count() {
+    return (METRIC_Lp - METRIC_INNER_PRODUCT) + 1 +
+            (METRIC_GOWER - METRIC_Canberra) + 1;
+}
+
 } // namespace faiss
 
 #endif

faiss/impl/AdditiveQuantizer.h

@@ -83,6 +83,7 @@ struct AdditiveQuantizer : Quantizer {
         ST_norm_lsq2x4, ///< use a 2x4 bits lsq as norm quantizer (for fast
                         ///< scan)
         ST_norm_rq2x4,  ///< use a 2x4 bits rq as norm quantizer (for fast scan)
+        ST_count
     };
 
     AdditiveQuantizer(

faiss/impl/ScalarQuantizer.h

@@ -33,6 +33,7 @@ struct ScalarQuantizer : Quantizer {
         QT_bf16,
         QT_8bit_direct_signed, ///< fast indexing of signed int8s ranging from
                                ///< [-128 to 127]
+        QT_count
     };
 
     QuantizerType qtype = QT_8bit;

faiss/impl/index_read.cpp

@@ -78,6 +78,32 @@
 
 namespace faiss {
 
+namespace {
+size_t max_deserialization_iters = 0;
+} // namespace
+
+size_t get_max_deserialization_iterations() {
+    return max_deserialization_iters;
+}
+
+void set_max_deserialization_iterations(size_t value) {
+    max_deserialization_iters = value;
+}
+
+#define FAISS_CHECK_DESERIALIZATION_ITERATIONS(val, field_name)      \
+    do {                                                             \
+        auto limit_ = get_max_deserialization_iterations();          \
+        if (limit_ > 0) {                                            \
+            FAISS_THROW_IF_NOT_FMT(                                  \
+                    static_cast<size_t>(val) <= limit_,              \
+                    "%s=%zd exceeds max_deserialization_iterations " \
+                    "limit %zd",                                     \
+                    field_name,                                      \
+                    static_cast<size_t>(val),                        \
+                    limit_);                                         \
+        }                                                            \
+    } while (0)
+
 /*************************************************************
  * Mmap-ing and viewing facilities
  **************************************************************/
@@ -371,6 +397,7 @@ std::unique_ptr<InvertedLists> read_InvertedLists_up(
     } else if (h == fourcc("ilpn") && !(io_flags & IO_FLAG_SKIP_IVF_DATA)) {
         size_t nlist, code_size, n_levels;
         READ1(nlist);
+        FAISS_CHECK_DESERIALIZATION_ITERATIONS(nlist, "ilpn nlist");
         READ1(code_size);
         READ1(n_levels);
         auto ailp = std::make_unique<ArrayInvertedListsPanorama>(
@@ -400,6 +427,7 @@ std::unique_ptr<InvertedLists> read_InvertedLists_up(
     } else if (h == fourcc("ilar") && !(io_flags & IO_FLAG_SKIP_IVF_DATA)) {
         auto ails = std::make_unique<ArrayInvertedLists>(0, 0);
         READ1(ails->nlist);
+        FAISS_CHECK_DESERIALIZATION_ITERATIONS(ails->nlist, "ilar nlist");
         READ1(ails->code_size);
         ails->ids.resize(ails->nlist);
         ails->codes.resize(ails->nlist);
@@ -430,6 +458,7 @@ std::unique_ptr<InvertedLists> read_InvertedLists_up(
         int h2 = (io_flags & 0xffff0000) | (fourcc("il__") & 0x0000ffff);
         size_t nlist, code_size;
         READ1(nlist);
+        FAISS_CHECK_DESERIALIZATION_ITERATIONS(nlist, "ilar skip nlist");
         READ1(code_size);
         std::vector<size_t> sizes(nlist);
         read_ArrayInvertedLists_sizes(f, sizes);
@@ -557,6 +586,7 @@ static void read_ProductAdditiveQuantizer(
             paq.nsplits > 0,
             "invalid ProductAdditiveQuantizer nsplits %zd (must be > 0)",
             paq.nsplits);
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(paq.nsplits, "nsplits");
 }
 
 static void read_ProductResidualQuantizer(
@@ -735,6 +765,8 @@ static void read_HNSW(HNSW& hnsw, IOReader* f) {
 static void read_NSG(NSG& nsg, IOReader* f) {
     READ1(nsg.ntotal);
     READ1(nsg.R);
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(nsg.ntotal, "nsg.ntotal");
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(nsg.R, "nsg.R");
     FAISS_THROW_IF_NOT_FMT(nsg.R > 0, "invalid NSG R %d (must be > 0)", nsg.R);
     READ1(nsg.L);
     READ1(nsg.C);
@@ -858,6 +890,7 @@ void read_ivf_header(
         std::vector<std::vector<idx_t>>* ids) {
     read_index_header(*ivf, f);
     READ1(ivf->nlist);
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(ivf->nlist, "nlist");
     READ1(ivf->nprobe);
     ivf->quantizer = read_index(f);
     ivf->own_fields = true;
@@ -1368,6 +1401,8 @@ std::unique_ptr<Index> read_index_up(IOReader* f, int io_flags) {
                 nt >= 0,
                 "invalid VectorTransform chain length %d (must be >= 0)",
                 nt);
+        FAISS_CHECK_DESERIALIZATION_ITERATIONS(
+                nt, "VectorTransform chain length");
         for (int i = 0; i < nt; i++) {
             ixpt->chain.push_back(read_VectorTransform(f));
         }
@@ -1898,6 +1933,7 @@ static void read_binary_ivf_header(
         std::vector<std::vector<idx_t>>* ids = nullptr) {
     read_index_binary_header(ivf, f);
     READ1(ivf.nlist);
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(ivf.nlist, "nlist");
     READ1(ivf.nprobe);
     ivf.quantizer = read_index_binary(f);
     ivf.own_fields = true;
@@ -1915,6 +1951,7 @@ static void read_binary_hash_invlists(
         IOReader* f) {
     size_t sz;
     READ1(sz);
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(sz, "binary hash invlists sz");
     int il_nbit = 0;
     READ1(il_nbit);
     FAISS_THROW_IF_NOT_FMT(
@@ -1965,6 +2002,7 @@ static void read_binary_multi_hash_map(
     size_t sz;
     READ1(id_bits);
     READ1(sz);
+    FAISS_CHECK_DESERIALIZATION_ITERATIONS(sz, "multi hash map sz");
     std::vector<uint8_t> buf;
     READVECTOR(buf);
     size_t nbit = add_no_overflow(
@@ -2063,6 +2101,7 @@ std::unique_ptr<IndexBinary> read_index_binary_up(IOReader* f, int io_flags) {
                 idxmh->nhash > 0,
                 "invalid IndexBinaryMultiHash nhash %d (must be > 0)",
                 idxmh->nhash);
+        FAISS_CHECK_DESERIALIZATION_ITERATIONS(idxmh->nhash, "nhash");
         READ1(idxmh->nflip);
         idxmh->maps.resize(idxmh->nhash);
         for (int i = 0; i < idxmh->nhash; i++) {

faiss/index_io.h

@@ -113,6 +113,17 @@ std::unique_ptr<InvertedLists> read_InvertedLists_up(
         IOReader* reader,
         int io_flags = 0);
 
+// Returns the current deserialization-iteration cap.
+// When nonzero, deserialization rejects loop-driving fields (nlist,
+// nsplits, VT chain length, nhash, etc.) that exceed this value.
+// Default: 0 (no limit).
+size_t get_max_deserialization_iterations();
+
+// Sets the deserialization-iteration cap.
+// NOT thread-safe: set before any concurrent deserialization calls
+// and do not modify while deserialization is in progress on other threads.
+void set_max_deserialization_iterations(size_t value);
+
 } // namespace faiss
 
 #endif

faiss/invlists/DirectMap.h

@@ -37,9 +37,10 @@ inline uint64_t lo_offset(uint64_t lo) {
  */
 struct DirectMap {
     enum Type {
-        NoMap = 0,    // default
-        Array = 1,    // sequential ids (only for add, no add_with_ids)
-        Hashtable = 2 // arbitrary ids
+        NoMap,     // default
+        Array,     // sequential ids (only for add, no add_with_ids)
+        Hashtable, // arbitrary ids
+        DMT_count
     };
     Type type;