Re: [PATCH] ALSA: pcm: Remove VLA usage

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Hi,

On Mar 13 2018 20:37, Takashi Iwai wrote:
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
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
  sound/core/pcm_native.c | 19 ++++++++++++-------
  1 file changed, 12 insertions(+), 7 deletions(-)

Yeah. I have concerned about it for a long time but kept it as is because it had no issue. Now, let's obsolete it.

Reviewed-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 77ba50ddcf9e..756a9a3884a5 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -323,7 +323,7 @@ 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;
@@ -331,7 +331,7 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
  	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.
@@ -339,8 +339,9 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
  	 * 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,


Thanks

Takashi Sakamoto
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