ALSA: pcm: Remove VLA usage

A helper function used by snd_pcm_hw_refine() still keeps using VLA
for timestamps of hw constraint rules that are non-fixed size.

Let's replace the VLA with a simple kmalloc() array.

Reference: https://lkml.org/lkml/2018/3/7/621
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -323,24 +323,25 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
 	struct snd_pcm_hw_constraints *constrs =
 					&substream->runtime->hw_constraints;
 	unsigned int k;
-	unsigned int rstamps[constrs->rules_num];
+	unsigned int *rstamps;
 	unsigned int vstamps[SNDRV_PCM_HW_PARAM_LAST_INTERVAL + 1];
 	unsigned int stamp;
 	struct snd_pcm_hw_rule *r;
 	unsigned int d;
 	struct snd_mask old_mask;
 	struct snd_interval old_interval;
 	bool again;
-	int changed;
+	int changed, err = 0;
 
 	/*
 	 * Each application of rule has own sequence number.
 	 *
 	 * Each member of 'rstamps' array represents the sequence number of
 	 * recent application of corresponding rule.
 	 */
-	for (k = 0; k < constrs->rules_num; k++)
-		rstamps[k] = 0;
+	rstamps = kcalloc(constrs->rules_num, sizeof(unsigned int), GFP_KERNEL);
+	if (!rstamps)
+		return -ENOMEM;
 
 	/*
 	 * Each member of 'vstamps' array represents the sequence number of
@@ -398,8 +399,10 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
 		}
 
 		changed = r->func(params, r);
-		if (changed < 0)
-			return changed;
+		if (changed < 0) {
+			err = changed;
+			goto out;
+		}
 
 		/*
 		 * When the parameter is changed, notify it to the caller
@@ -430,7 +433,9 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
 	if (again)
 		goto retry;
 
-	return 0;
+ out:
+	kfree(rstamps);
+	return err;
 }
 
 static int fixup_unreferenced_params(struct snd_pcm_substream *substream,