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 5.4-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-5.4 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 @@ -266,6 +266,7 @@ 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 || @@ -282,6 +283,8 @@ 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-5.4/alsa-ctl-fix-copy-of-updated-id-with-element-read-write.patch