FAILED: patch "[PATCH] ALSA: pcm: Call substream ack() method upon compat mmap" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

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 to <stable@vger.kernel.org>.

thanks,

greg k-h

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

From 2e2832562c877e6530b8480982d99a4ff90c6777 Mon Sep 17 00:00:00 2001
From: Alan Young <consult.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 Young <consult.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 Iwai <tiwai@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;