Re: FAILED: patch "[PATCH] ALSA: pcm: Call substream ack() method upon compat mmap" failed to apply to 4.14-stable tree

[Alan Young <consult.awy@gmail.com>]

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 4.14-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;
>