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Fix size_t overflow in encoder CreatePreparedDictionaryWithParams (32-bit) #1452

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Fix size_t overflow in encoder CreatePreparedDictionaryWithParams (32-bit) #1452

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d07ae4d
Fix size_t overflow in CreatePreparedDictionaryWithParams on 32-bit
0xazanul Apr 11, 2026
0eebdf1
Replace arithmetic overflow guard with protocol-level size cap
0xazanul Apr 15, 2026
0584537
Merge branch 'master' into fix/enc-prepared-dictionary-alloc-overflow
0xazanul Apr 15, 2026
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12 changes: 9 additions & 3 deletions c/enc/compound_dictionary.c
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,10 @@
#include <brotli/shared_dictionary.h>
#include "memory.h"

/* Brotli cannot reference dictionary data beyond 64 MiB (1 << 26).
Accept up to 256 MiB (1 << 28) as a generous upper bound. */
#define BROTLI_MAX_PREPARED_DICTIONARY_SIZE ((size_t)1 << 28)

static PreparedDictionary* CreatePreparedDictionaryWithParams(MemoryManager* m,
const uint8_t* source, size_t source_size, uint32_t bucket_bits,
uint32_t slot_bits, uint32_t hash_bits, uint16_t bucket_limit) {
Expand All @@ -19,11 +23,11 @@ static PreparedDictionary* CreatePreparedDictionaryWithParams(MemoryManager* m,
uint32_t hash_shift = 64u - bucket_bits;
uint64_t hash_mask = (~((uint64_t)0U)) >> (64 - hash_bits);
uint32_t slot_mask = num_slots - 1;
size_t alloc_size = (sizeof(uint32_t) << slot_bits) +
size_t header_size = (sizeof(uint32_t) << slot_bits) +
(sizeof(uint32_t) << slot_bits) +
(sizeof(uint16_t) << bucket_bits) +
(sizeof(uint32_t) << bucket_bits) +
(sizeof(uint32_t) * source_size);
(sizeof(uint32_t) << bucket_bits);
size_t alloc_size;
uint8_t* flat = NULL;
PreparedDictionary* result = NULL;
uint16_t* num = NULL;
Expand All @@ -40,6 +44,8 @@ static PreparedDictionary* CreatePreparedDictionaryWithParams(MemoryManager* m,
if (slot_bits > 16) return NULL;
if (slot_bits > bucket_bits) return NULL;
if (bucket_bits - slot_bits >= 16) return NULL;
if (source_size > BROTLI_MAX_PREPARED_DICTIONARY_SIZE) return NULL;
alloc_size = header_size + (sizeof(uint32_t) * source_size);

flat = BROTLI_ALLOC(m, uint8_t, alloc_size);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(flat)) return NULL;
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