On Tue, 12 Oct 2021 18:41:19 +0200, Pierre-Louis Bossart wrote:
On 10/12/21 10:27 AM, Takashi Iwai wrote:
On Tue, 12 Oct 2021 17:15:56 +0200, Pierre-Louis Bossart wrote:
In either way, the new_ptr has to be validated beforehand that it's within 0..boundary-1. (old_ptr is assumed to be valid.)
In the 3 of the calls to pcm_lib_apply_appl_ptr(), the check is done already prior to calling that function if (appl_ptr >= runtime->boundary) appl_ptr -= runtime->boundary; err = pcm_lib_apply_appl_ptr(substream, appl_ptr);
it's rather unclear to me why the same check is not done for sync_ptr, e.g.
if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL)) { err = pcm_lib_apply_appl_ptr(substream, sync_ptr.c.control.appl_ptr);
if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL)) { err = pcm_lib_apply_appl_ptr(substream, scontrol.appl_ptr);
Should I add a check there, or add a check inside of pcm_lib_apply_appl_ptr() which would be a duplicate in the majority of cases?
I guess adding in pcm_lib_appl_appl_ptr() would be easier and safer. There is even one more place that is calling pcm_lib_apply_appl_ptr() in the very latest commit (a fix for a buggy 32bit compat ioctl).
ok, here's the code I'll start testing. Thanks a lot Takashi for your help.
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;
/* 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.
thanks,
Takashi