This is a note to let you know that I've just added the patch titled
ALSA: ctl: Fix copy of updated id with element read/write
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-ctl-fix-copy-of-updated-id-with-element-read-write.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b6409dd6bdc03aa178bbff0d80db2a30d29b63ac Mon Sep 17 00:00:00 2001
From: Alan Young <consult.awy@xxxxxxxxx>
Date: Thu, 2 Dec 2021 15:06:07 +0000
Subject: ALSA: ctl: Fix copy of updated id with element read/write
From: Alan Young <consult.awy@xxxxxxxxx>
commit b6409dd6bdc03aa178bbff0d80db2a30d29b63ac upstream.
When control_compat.c:copy_ctl_value_to_user() is used, by
ctl_elem_read_user() & ctl_elem_write_user(), it must also copy back the
snd_ctl_elem_id value that may have been updated (filled in) by the call
to snd_ctl_elem_read/snd_ctl_elem_write().
This matches the functionality provided by snd_ctl_elem_read_user() and
snd_ctl_elem_write_user(), via snd_ctl_build_ioff().
Without this, and without making additional calls to snd_ctl_info()
which are unnecessary when using the non-compat calls, a userspace
application will not know the numid value for the element and
consequently will not be able to use the poll/read interface on the
control file to determine which elements have updates.
Signed-off-by: Alan Young <consult.awy@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211202150607.543389-1-consult.awy@xxxxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/control_compat.c | 3 +++
1 file changed, 3 insertions(+)
--- a/sound/core/control_compat.c
+++ b/sound/core/control_compat.c
@@ -281,6 +281,7 @@ static int copy_ctl_value_to_user(void _
struct snd_ctl_elem_value *data,
int type, int count)
{
+ struct snd_ctl_elem_value32 __user *data32 = userdata;
int i, size;
if (type == SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
@@ -297,6 +298,8 @@ static int copy_ctl_value_to_user(void _
if (copy_to_user(valuep, data->value.bytes.data, size))
return -EFAULT;
}
+ if (copy_to_user(&data32->id, &data->id, sizeof(data32->id)))
+ return -EFAULT;
return 0;
}
Patches currently in stable-queue which might be from consult.awy@xxxxxxxxx are
queue-4.9/alsa-ctl-fix-copy-of-updated-id-with-element-read-write.patch
