fix: seqLoadStatus OOB reads/writes for custom SAF sequences (#6917)

Custom SAF sequence IDs can exceed sequenceMapSize, causing out-of-bounds
reads/writes on the seqLoadStatus byte array (sized exactly sequenceMapSize).

This is the direct cause of intermittent battle music failure with BGM packs
(issue #5706): on the second encounter, AudioLoad_SyncLoadSeq reads a garbage
value from heap memory past seqLoadStatus[] and may find 1 (loading in
progress), causing it to return NULL early — the sequence player is never
initialized and no battle music plays.

Symmetric fix to the fontLoadStatus guards in PR #6916:
- AudioLoad_IsSeqLoadComplete: return true for OOB seqIds (custom SAF
  sequences are resource-manager-backed, not in the async-load status table)
- AudioLoad_SetSeqLoadStatus: skip update for seqId >= sequenceMapSize
- AudioLoad_SyncLoadSeq: skip the in-progress check for OOB seqIds

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/soh/src/code/audio_load.c b/soh/src/code/audio_load.c
index 85c0ed709..582cf3a1c 100644
--- a/soh/src/code/audio_load.c
+++ b/soh/src/code/audio_load.c
@@ -315,13 +315,19 @@ s32 AudioLoad_IsFontLoadComplete(s32 fontId) {
 s32 AudioLoad_IsSeqLoadComplete(s32 seqId) {
     if (seqId == 0xFF) {
         return true;
-    } else if (gAudioContext.seqLoadStatus[seqId] >= 2) {
+    }
+    if ((size_t)seqId >= sequenceMapSize) {
+        // Custom SAF sequence whose seqId exceeds the status table — not async-loading, treat as ready.
         return true;
-    } else if (gAudioContext.seqLoadStatus[AudioLoad_GetRealTableIndex(SEQUENCE_TABLE, seqId)] >= 2) {
+    }
+    if (gAudioContext.seqLoadStatus[seqId] >= 2) {
+        return true;
+    }
+    s32 realId = (s32)AudioLoad_GetRealTableIndex(SEQUENCE_TABLE, seqId);
+    if ((size_t)realId < sequenceMapSize && gAudioContext.seqLoadStatus[realId] >= 2) {
         return true;
-    } else {
-        return false;
     }
+    return false;
 }
 
 s32 AudioLoad_IsSampleLoadComplete(s32 sampleBankId) {
@@ -343,7 +349,7 @@ void AudioLoad_SetFontLoadStatus(s32 fontId, s32 status) {
 }
 
 void AudioLoad_SetSeqLoadStatus(s32 seqId, s32 status) {
-    if ((seqId != 0xFF) && (gAudioContext.seqLoadStatus[seqId] != 5)) {
+    if ((seqId != 0xFF) && ((size_t)seqId < sequenceMapSize) && (gAudioContext.seqLoadStatus[seqId] != 5)) {
         gAudioContext.seqLoadStatus[seqId] = status;
     }
 }
@@ -637,7 +643,7 @@ u8* AudioLoad_SyncLoadSeq(s32 seqId) {
     s32 pad;
     s32 didAllocate;
 
-    if (gAudioContext.seqLoadStatus[AudioLoad_GetRealTableIndex(SEQUENCE_TABLE, seqId)] == 1) {
+    if ((size_t)seqId < sequenceMapSize && gAudioContext.seqLoadStatus[seqId] == 1) {
         return NULL;
     }