msacm32: Avoid attempts to convert data when available output is negative in acmStreamConvert

[Bruno Jesus]

Signed-off-by: Bruno Jesus <00cpxxx at gmail.com>

The game Lost Horizon passes a negative value in cbDstLength while
calling acmStreamConvert, this means we can't do the conversion
because there is no output buffer available. Cast required since the
value is DWORD.

Fixes https://bugs.winehq.org/show_bug.cgi?id=24723
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diff --git a/dlls/msacm32/stream.c b/dlls/msacm32/stream.c
index bdfc3cc..67c5ce9 100644
--- a/dlls/msacm32/stream.c
+++ b/dlls/msacm32/stream.c
@@ -88,20 +88,25 @@ MMRESULT WINAPI acmStreamConvert(HACMSTREAM has, PACMSTREAMHEADER pash,
 
     if ((was = ACM_GetStream(has)) == NULL) {
         WARN("invalid handle\n");
-	return MMSYSERR_INVALHANDLE;
+        return MMSYSERR_INVALHANDLE;
     }
     if (!pash || pash->cbStruct < sizeof(ACMSTREAMHEADER)) {
         WARN("invalid parameter\n");
-	return MMSYSERR_INVALPARAM;
+        return MMSYSERR_INVALPARAM;
     }
     if (!(pash->fdwStatus & ACMSTREAMHEADER_STATUSF_PREPARED)) {
         WARN("unprepared header\n");
-	return ACMERR_UNPREPARED;
+        return ACMERR_UNPREPARED;
     }
 
     pash->cbSrcLengthUsed = 0;
     pash->cbDstLengthUsed = 0;
 
+    if ((LONG) pash->cbDstLength < 0) {
+        WARN("invalid output length\n");
+        return MMSYSERR_INVALPARAM;
+    }
+
     /* Note: the ACMSTREAMHEADER and ACMDRVSTREAMHEADER structs are of same
      * size. some fields are private to msacm internals, and are exposed
      * in ACMSTREAMHEADER in the dwReservedDriver array
diff --git a/dlls/msacm32/tests/msacm.c b/dlls/msacm32/tests/msacm.c
index 4c9dca0..3b5a446 100644
--- a/dlls/msacm32/tests/msacm.c
+++ b/dlls/msacm32/tests/msacm.c
@@ -527,7 +527,7 @@ static void test_prepareheader(void)
     WAVEFORMATEX dst;
     MMRESULT mr;
     ACMSTREAMHEADER hdr;
-    BYTE buf[sizeof(WAVEFORMATEX) + 32], pcm[512], input[512];
+    BYTE buf[sizeof(WAVEFORMATEX) + 32], pcm[2048], input[512];
     ADPCMCOEFSET *coef;
 
     src = (ADPCMWAVEFORMAT*)buf;
@@ -567,6 +567,7 @@ static void test_prepareheader(void)
     mr = acmStreamOpen(&has, NULL, (WAVEFORMATEX*)src, &dst, NULL, 0, 0, 0);
     ok(mr == MMSYSERR_NOERROR, "open failed: 0x%x\n", mr);
 
+    memset(input, 0, sizeof(input));
     memset(&hdr, 0, sizeof(hdr));
     hdr.cbStruct = sizeof(hdr);
     hdr.pbSrc = input;
@@ -594,10 +595,37 @@ static void test_prepareheader(void)
     ok(mr == MMSYSERR_NOERROR, "prepare failed: 0x%x\n", mr);
     ok(hdr.fdwStatus == (ACMSTREAMHEADER_STATUSF_PREPARED | ACMSTREAMHEADER_STATUSF_DONE), "header wasn't prepared: 0x%x\n", hdr.fdwStatus);
 
+    hdr.fdwStatus &= ~ACMSTREAMHEADER_STATUSF_DONE;
+    mr = acmStreamConvert(has, &hdr, ACM_STREAMCONVERTF_BLOCKALIGN);
+    ok(mr == MMSYSERR_NOERROR, "convert failed: 0x%x\n", mr);
+    ok(hdr.fdwStatus & ACMSTREAMHEADER_STATUSF_DONE, "conversion was not done: 0x%x\n", hdr.fdwStatus);
+
     mr = acmStreamUnprepareHeader(has, &hdr, 0);
     ok(mr == MMSYSERR_NOERROR, "unprepare failed: 0x%x\n", mr);
     ok(hdr.fdwStatus == ACMSTREAMHEADER_STATUSF_DONE, "header wasn't unprepared: 0x%x\n", hdr.fdwStatus);
 
+    memset(&hdr, 0, sizeof(hdr));
+    hdr.cbStruct = sizeof(hdr);
+    hdr.pbSrc = input;
+    hdr.cbSrcLength = sizeof(input);
+    hdr.pbDst = pcm;
+    hdr.cbDstLength = sizeof(pcm);
+
+    mr = acmStreamPrepareHeader(has, &hdr, 0);
+    ok(mr == MMSYSERR_NOERROR, "prepare failed: 0x%x\n", mr);
+    ok(hdr.fdwStatus == ACMSTREAMHEADER_STATUSF_PREPARED, "header wasn't prepared: 0x%x\n", hdr.fdwStatus);
+
+    hdr.cbDstLength = -4; /* Test for Lost Horizon (bug 24723) */
+    hdr.cbDstLengthUsed = 12345;
+    mr = acmStreamConvert(has, &hdr, ACM_STREAMCONVERTF_BLOCKALIGN);
+    ok(mr == MMSYSERR_INVALPARAM, "expected 11, got %d!\n", mr);
+    ok(hdr.cbDstLengthUsed == 0, "expected 0, got %d\n", hdr.cbDstLengthUsed);
+
+    hdr.cbDstLength = sizeof(pcm);
+    mr = acmStreamUnprepareHeader(has, &hdr, 0);
+    ok(mr == MMSYSERR_NOERROR, "unprepare failed: 0x%x\n", mr);
+    ok(hdr.fdwStatus == 0, "header wasn't unprepared: 0x%x\n", hdr.fdwStatus);
+
     mr = acmStreamClose(has, 0);
     ok(mr == MMSYSERR_NOERROR, "close failed: 0x%x\n", mr);
 }