[PATCH v2] pcm_native: Remove VLA usage

[PATCH v2] pcm_native: Remove VLA usage

[Kyle Spiers]

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@spiers.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

Re: [PATCH v2] pcm_native: Remove VLA usage

[Takashi Sakamoto]

Hi,

On Mar 29 2018 07:24, Kyle Spiers wrote:
> 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@spiers.me>
> ---
>   sound/core/pcm_native.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)

This bug was already fixed at a commit 5730f9f744cf ('
ALSA: pcm: Remove VLA usage')[1][2].

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/commit/sound/core/pcm_native.c?h=for-next&id=5730f9f744cfe20b771adc33f3b476b95d3eebba
[2] 
http://mailman.alsa-project.org/pipermail/alsa-devel/2018-March/133268.html


Thanks

Takashi Sakamoto

Re: [PATCH v2] pcm_native: Remove VLA usage

[Takashi Iwai]

On Thu, 29 Mar 2018 00:24:00 +0200,
Kyle Spiers wrote:
> 
> 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@spiers.me>

It's been already fixed weeks ago...


thanks,

Takashi