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Fix potential infinite loop in merge_command_sequences (merging.c)

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Add safeguards against infinite loops caused by:
- Zero-count commands that don't advance position
- Malformed command sequences that never converge

Add iteration limit based on total command length.
This commit is contained in:
Trung Lê 2026-02-04 10:32:35 +11:00
parent 2ad9616586
commit 3d81b47e83
1 changed files with 17 additions and 2 deletions
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19
tools/lz/merging.c
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@ -70,7 +70,14 @@ struct command * merge_command_sequences (const struct command * current, unsign
const struct command * saved_current;
const struct command * saved_new;
unsigned short current_pos, new_pos;
// Track iteration limit to prevent infinite loops from malformed input
unsigned int iteration_limit = (unsigned int)current_length + new_length + 1;
unsigned int iterations = 0;
while (current_length) {
if (++iterations > iteration_limit) {
// Prevent infinite loop from malformed command sequences
break;
}
if (current -> count == new -> count) {
*(current_command ++) = pick_best_command(2, *(current ++), *(new ++));
current_length --;
@ -81,12 +88,20 @@ struct command * merge_command_sequences (const struct command * current, unsign
current_pos = (current ++) -> count;
new_pos = (new ++) -> count;
current_length --;
while (current_pos != new_pos)
while (current_pos != new_pos) {
if (++iterations > iteration_limit) {
// Prevent infinite loop from zero-count commands
break;
}
if (current_pos < new_pos) {
if (current -> count == 0) break; // Prevent infinite loop
current_pos += (current ++) -> count;
current_length --;
} else
} else {
if (new -> count == 0) break; // Prevent infinite loop
new_pos += (new ++) -> count;
}
}
current_pos = compressed_length(saved_current, current - saved_current);
new_pos = compressed_length(saved_new, new - saved_new);
if (new_pos < current_pos) {