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SubjectRe: [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@suse.de>
> ---
> 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@sakamocchi.jp>

> 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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