linux-kernel - [PATCH v2] pcm_native: Remove VLA usage

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Message-Id: <1522275840-14092-1-git-send-email-kyle@spiers.me>
Date:   Wed, 28 Mar 2018 15:24:00 -0700
From:   Kyle Spiers <kyle@...ers.me>
To:     perex@...ex.cz
Cc:     tiwai@...e.com, o-takashi@...amocchi.jp,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        keescook@...omium.org, Kyle Spiers <kyle@...ers.me>
Subject: [PATCH v2] pcm_native: Remove VLA usage

As part of the effort to remove VLAs from the kernel[1], this changes
the allocation of the rstamps array from being on the stack to being
kcalloc()ed. This also allows for the removal of the explicit zeroing
loop.

Signed-off-by: Kyle Spiers <kyle@...ers.me>
---
 sound/core/pcm_native.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 77ba50d..db5e3c5 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;
@@ -339,8 +339,8 @@ 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(*rstamps), GFP_KERNEL);
 
 	/*
 	 * Each member of 'vstamps' array represents the sequence number of
@@ -398,8 +398,10 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
 		}
 
 		changed = r->func(params, r);
-		if (changed < 0)
+		if (changed < 0) {
+			kfree(rstamps);
 			return changed;
+		}
 
 		/*
 		 * When the parameter is changed, notify it to the caller
@@ -430,6 +432,7 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
 	if (again)
 		goto retry;
 
+	kfree(rstamps);
 	return 0;
 }
 
-- 
2.7.4