Audio: MFCC: Fix memory leak on reset-prepare cycles

mfcc_reset() did not free buffers allocated by mfcc_setup(), so a
stop->reset->prepare->start cycle would leak all MFCC allocations
(FFT buffers, mel filterbank, DCT matrix, lifter, VAD buffers).

This patch fixes the issue by calling mfcc_free_buffers() from
mfcc_reset(). The pointers are set to NULL after free via a helper
function mfcc_free_and_null(), so mfcc_free() won't double-free
when it calls mfcc_free_buffers() again later.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>

Author: singalsu

src/audio/mfcc/mfcc.c

@@ -197,6 +197,11 @@ static int mfcc_reset(struct processing_module *mod)
 
 	comp_info(mod->dev, "entry");
 
+	/* Free MFCC buffers to prevent leaks on reset->prepare cycles.
+	 * mfcc_free_buffers() NULLs the pointers after free.
+	 */
+	mfcc_free_buffers(mod);
+
 	/* Reset to similar state as init() */
 	cd->mfcc_func = NULL;
 	return 0;

src/audio/mfcc/mfcc_setup.c

@@ -396,17 +396,27 @@ int mfcc_setup(struct processing_module *mod, int max_frames, int sample_rate, i
 	return ret;
 }
 
+static void mfcc_free_and_null(struct processing_module *mod, void **ptr)
+{
+	mod_free(mod, *ptr);
+	*ptr = NULL;
+}
+
+/* Free MFCC buffers to prevent leaks on reset->prepare cycles.
+ * mfcc_free_buffers() NULLs the pointers after free.
+ */
 void mfcc_free_buffers(struct processing_module *mod)
 {
 	struct mfcc_comp_data *cd = module_get_private_data(mod);
 
 	mod_fft_plan_free(mod, cd->state.fft.fft_plan);
-	mod_free(mod, cd->state.fft.fft_buf);
-	mod_free(mod, cd->state.fft.fft_out);
-	mod_free(mod, cd->state.buffers);
-	mod_free(mod, cd->state.melfb.data);
-	mod_free(mod, cd->state.dct.matrix);
-	mod_free(mod, cd->state.lifter.matrix);
-	mod_free(mod, cd->vad.noise_floor);
-	mod_free(mod, cd->vad.weights);
+	cd->state.fft.fft_plan = NULL;
+	mfcc_free_and_null(mod, (void **)&cd->state.fft.fft_buf);
+	mfcc_free_and_null(mod, (void **)&cd->state.fft.fft_out);
+	mfcc_free_and_null(mod, (void **)&cd->state.buffers);
+	mfcc_free_and_null(mod, (void **)&cd->state.melfb.data);
+	mfcc_free_and_null(mod, (void **)&cd->state.dct.matrix);
+	mfcc_free_and_null(mod, (void **)&cd->state.lifter.matrix);
+	mfcc_free_and_null(mod, (void **)&cd->vad.noise_floor);
+	mfcc_free_and_null(mod, (void **)&cd->vad.weights);
 }