linux-kernel - [PATCH] ALSA: pcm: Remove VLA usage

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Date:   Tue, 13 Mar 2018 12:37:58 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     alsa-devel@...a-project.org
Cc:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] 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
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 sound/core/pcm_native.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

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,
-- 
2.16.2