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llama.cpp
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grammar: fix stack overflow using cycle detection and depth limit

This commit is contained in:
tdevelope 2026-01-21 13:40:32 +02:00
parent 8cc0ba957b
commit 364007affd
1 changed files with 22 additions and 2 deletions
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24
src/llama-grammar.cpp
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@ -10,6 +10,7 @@
#include <stdexcept>
#define MAX_REPETITION_THRESHOLD 2000
static constexpr uint32_t MAX_GRAMMAR_RECURSION_DEPTH = 2000;
//
// helpers
//
@ -830,7 +831,16 @@ static bool llama_grammar_match_token(
static void llama_grammar_advance_stack(
const llama_grammar_rules & rules,
const llama_grammar_stack & stack,
llama_grammar_stacks & new_stacks) {
llama_grammar_stacks & new_stacks,
std::vector<llama_grammar_stack> & history) {
if (history.size() >= MAX_GRAMMAR_RECURSION_DEPTH) {
return;
}
if (std::find(history.begin(), history.end(), stack) != history.end()) {
return;
}
if (stack.empty()) {
if (std::find(new_stacks.begin(), new_stacks.end(), stack) == new_stacks.end()) {
new_stacks.emplace_back(stack);
@ -855,7 +865,9 @@ static void llama_grammar_advance_stack(
// if alternate is nonempty, add to stack
new_stack.push_back(subpos);
}
llama_grammar_advance_stack(rules, new_stack, new_stacks);
history.push_back(stack);
llama_grammar_advance_stack(rules, new_stack, new_stacks, history);
history.pop_back();
while (!llama_grammar_is_end_of_sequence(subpos)) {
// scan to end of alternate def
subpos++;
@ -887,6 +899,14 @@ static void llama_grammar_advance_stack(
}
}
static void llama_grammar_advance_stack(
const llama_grammar_rules & rules,
const llama_grammar_stack & stack,
llama_grammar_stacks & new_stacks) {
std::vector<llama_grammar_stack> history;
llama_grammar_advance_stack(rules, stack, new_stacks, history);
}
static llama_grammar_candidates llama_grammar_reject_candidates(
const llama_grammar_rules & rules,
const llama_grammar_stacks & stacks,