Re: [alsa-devel] [PATCH] pcm_native: Remove VLA usage

On Wed, Mar 28, 2018 at 3:11 PM, Kyle Spiers kyle@spiers.me 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.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Kyle Spiers kyle@spiers.me

sound/core/pcm_native.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 77ba50d..57240b8 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
  

@@ -399,6 +399,7 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,

            changed = r->func(params, r);
            if (changed < 0)

•                   kfree(rstamps);
                    return changed;
  

Whoops, this needs { } s:

if (changed < 0) { kfree(rstamps); return changed; }

Otherwise, looks good! Once that's fixed:

Reviewed-by: Kees Cook keescook@chromium.org

-Kees

            /*

@@ -430,6 +431,7 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream, if (again) goto retry;

•   kfree(rstamps);
    return 0;
  

}

-- 2.7.4