hw/audio/sb16: Restrict I/O sampling rate range for command 41h/42h

The I/O sampling rate range is enforced to 5000 to 45000HZ according to
commit a2cd86a9. Setting I/O sampling rate with command 41h/42h, a guest
user can break this assumption and trigger an assertion in audio_calloc
via command 0xd4. This patch restricts the I/O sampling rate range for
command 41h/42h.

Fixes: 85571bc7415 ("audio merge (malc)")
Signed-off-by: Qiang Liu <cyruscyliu@gmail.com>
Message-Id: <1624502687-5214-1-git-send-email-cyruscyliu@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 19 insertions, 12 deletions

diff --git a/hw/audio/sb16.c b/hw/audio/sb16.c
index 5cf121f..60f1f75 100644
--- a/hw/audio/sb16.c
+++ b/hw/audio/sb16.c
@@ -229,6 +229,23 @@ static void continue_dma8 (SB16State *s)
     control (s, 1);
 }
 
+static inline int restrict_sampling_rate(int freq)
+{
+    if (freq < SAMPLE_RATE_MIN) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "sampling range too low: %d, increasing to %u\n",
+                      freq, SAMPLE_RATE_MIN);
+        return SAMPLE_RATE_MIN;
+    } else if (freq > SAMPLE_RATE_MAX) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "sampling range too high: %d, decreasing to %u\n",
+                      freq, SAMPLE_RATE_MAX);
+        return SAMPLE_RATE_MAX;
+    } else {
+        return freq;
+    }
+}
+
 static void dma_cmd8 (SB16State *s, int mask, int dma_len)
 {
     s->fmt = AUDIO_FORMAT_U8;
@@ -244,17 +261,7 @@ static void dma_cmd8 (SB16State *s, int mask, int dma_len)
         int tmp = (256 - s->time_const);
         s->freq = (1000000 + (tmp / 2)) / tmp;
     }
-    if (s->freq < SAMPLE_RATE_MIN) {
-        qemu_log_mask(LOG_GUEST_ERROR,
-                      "sampling range too low: %d, increasing to %u\n",
-                      s->freq, SAMPLE_RATE_MIN);
-        s->freq = SAMPLE_RATE_MIN;
-    } else if (s->freq > SAMPLE_RATE_MAX) {
-        qemu_log_mask(LOG_GUEST_ERROR,
-                      "sampling range too high: %d, decreasing to %u\n",
-                      s->freq, SAMPLE_RATE_MAX);
-        s->freq = SAMPLE_RATE_MAX;
-    }
+    s->freq = restrict_sampling_rate(s->freq);
 
     if (dma_len != -1) {
         s->block_size = dma_len << s->fmt_stereo;
@@ -768,7 +775,7 @@ static void complete (SB16State *s)
              * and FT2 sets output freq with this (go figure).  Compare:
              * http://homepages.cae.wisc.edu/~brodskye/sb16doc/sb16doc.html#SamplingRate
              */
-            s->freq = dsp_get_hilo (s);
+            s->freq = restrict_sampling_rate(dsp_get_hilo(s));
             ldebug ("set freq %d\n", s->freq);
             break;