On Tue, 12 Oct 2021 20:02:07 +0200, Pierre-Louis Bossart wrote:
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index a144a3f68e9e..e839459916ca 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -2127,11 +2127,30 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream, { struct snd_pcm_runtime *runtime = substream->runtime; snd_pcm_uframes_t old_appl_ptr = runtime->control->appl_ptr;
snd_pcm_sframes_t diff; int ret; if (old_appl_ptr == appl_ptr) return 0;/** check if a rewind is requested by the application, after* verifying the new appl_ptr is in the 0..boundary range*/if (substream->runtime->info & SNDRV_PCM_INFO_NO_REWINDS) {if (appl_ptr >= runtime->boundary)appl_ptr -= runtime->boundary;The boundary check can (or should) be done unconditionally. It was too naive to assume a sane appl_ptr passed always. And, it can rather return an error. So,
if (appl_ptr >= runtime->boundary) return -EINVAL;
ok, but that would be a separate patch then since it impacts all users, even without the NO_REWINDS.
Makes sense.
/* check if a rewind is requested by the application */ if (substream->runtime->info & SNDRV_PCM_INFO_NO_REWINDS) { diff = appl_ptr - old_appl_ptr; ....
if (diff >= 0) {if (diff > runtime->buffer_size)return 0;} else {if (runtime->boundary + diff > runtime->buffer_size)return 0;I'm not sure whether we should return 0 here. In snd_pcm_rewind() it returns 0 due to application breakage, though.
We could return -EINVAL indeed, that would keep the work-around in place for PulseAudio. Even for other uses, it's not so bad: the selection of NO_REWINDS is an opt-in, and if a rewind still occurs a big fail would help detect a configuration issue.
Yeah, that was my gut feeling ,too.
Takashi