alac: Limit max_samples_per_frame

Otherwise buffer size calculations in allocate_buffers could
overflow later, making the code think a large enough buffer
actually was allocated.

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/alac.c

@@ -494,7 +494,8 @@ static int alac_set_info(ALACContext *alac)
     bytestream2_skipu(&gb, 12); // size:4, alac:4, version:4
 
     alac->max_samples_per_frame = bytestream2_get_be32u(&gb);
-    if (!alac->max_samples_per_frame || alac->max_samples_per_frame > INT_MAX) {
+    if (!alac->max_samples_per_frame ||
+        alac->max_samples_per_frame > INT_MAX / sizeof(int32_t)) {
         av_log(alac->avctx, AV_LOG_ERROR, "max samples per frame invalid: %u\n",
                alac->max_samples_per_frame);
         return AVERROR_INVALIDDATA;