This commit is not applicable before the 64-bit time_t in user space with 32-bit compatibility changes introduces by 80fe7430c7085951d1246d83f638cc17e6c0be36 in 5.6.

On 26/07/2021 09:09, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id tostable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2e2832562c877e6530b8480982d99a4ff90c6777 Mon Sep 17 00:00:00 2001 From: Alan Youngconsult.awy@gmail.com Date: Fri, 9 Jul 2021 09:48:54 +0100 Subject: [PATCH] ALSA: pcm: Call substream ack() method upon compat mmap commit

If a 32-bit application is being used with a 64-bit kernel and is using the mmap mechanism to write data, then the SNDRV_PCM_IOCTL_SYNC_PTR ioctl results in calling snd_pcm_ioctl_sync_ptr_compat(). Make this use pcm_lib_apply_appl_ptr() so that the substream's ack() method, if defined, is called.

The snd_pcm_sync_ptr() function, used in the 64-bit ioctl case, already uses snd_pcm_ioctl_sync_ptr_compat().

Fixes: 9027c4639ef1 ("ALSA: pcm: Call ack() whenever appl_ptr is updated") Signed-off-by: Alan Youngconsult.awy@gmail.com Cc:stable@vger.kernel.org Link:https://lore.kernel.org/r/c441f18c-eb2a-3bdd-299a-696ccca2de9c@gmail.com Signed-off-by: Takashi Iwaitiwai@suse.de

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 14e32825c339..c88c4316c417 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -3063,9 +3063,14 @@ static int snd_pcm_ioctl_sync_ptr_compat(struct snd_pcm_substream *substream, boundary = 0x7fffffff; snd_pcm_stream_lock_irq(substream); /* FIXME: we should consider the boundary for the sync from app */

• if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL))

• control->appl_ptr = scontrol.appl_ptr;
  

• else

• if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL)) {

• err = pcm_lib_apply_appl_ptr(substream,
  

• 		scontrol.appl_ptr);
  

• if (err < 0) {
  

• 	snd_pcm_stream_unlock_irq(substream);
  

• 	return err;
  

• }
  

• } else scontrol.appl_ptr = control->appl_ptr % boundary; if (!(sflags & SNDRV_PCM_SYNC_PTR_AVAIL_MIN)) control->avail_min = scontrol.avail_min;