Patch "Revert "ALSA: usb-audio: purge needless variable length array"" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

Revert "ALSA: usb-audio: purge needless variable length array"

to the 4.11-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:
revert-alsa-usb-audio-purge-needless-variable-length-array.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Tue, 30 May 2017 09:23:41 +0200
Subject: Revert "ALSA: usb-audio: purge needless variable length array"

From: Takashi Iwai <[email protected]>

commit 64188cfbe5245d412de2139a3864e4e00b4136f0 upstream.

This reverts commit 89b593c30e83 ("ALSA: usb-audio: purge needless variable length array"). The patch turned out to cause a severe regression, triggering an Oops at snd_usb_ctl_msg(). It was overseen that snd_usb_ctl_msg() writes back the response to the given buffer, while the patch changed it to a read-only const buffer. (One should always double-check when an extra pointer cast is present...)

As a simple fix, just revert the affected commit. It was merely a cleanup. Although it brings VLA again, it's clearer as a fix. We'll address the VLA later in another patch.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195875

---
 sound/usb/mixer_us16x08.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

@@ -698,12 +698,12 @@ static int snd_us16x08_meter_get(struct
 	struct snd_usb_audio *chip = elem->head.mixer->chip;
 	struct snd_us16x08_meter_store *store = elem->private_data;
 	u8 meter_urb[64];
-	char tmp[sizeof(mix_init_msg2)] = {0};
+	char tmp[max(sizeof(mix_init_msg1), sizeof(mix_init_msg2))];
 
 	switch (kcontrol->private_value) {
 	case 0:
-		snd_us16x08_send_urb(chip, (char *)mix_init_msg1,
-				     sizeof(mix_init_msg1));
+		memcpy(tmp, mix_init_msg1, sizeof(mix_init_msg1));
+		snd_us16x08_send_urb(chip, tmp, 4);
 		snd_us16x08_recv_urb(chip, meter_urb,
 			sizeof(meter_urb));
 		kcontrol->private_value++;

@@ -721,7 +721,7 @@ static int snd_us16x08_meter_get(struct
 	case 3:
 		memcpy(tmp, mix_init_msg2, sizeof(mix_init_msg2));
 		tmp[2] = snd_get_meter_comp_index(store);
-		snd_us16x08_send_urb(chip, tmp, sizeof(mix_init_msg2));
+		snd_us16x08_send_urb(chip, tmp, 10);
 		snd_us16x08_recv_urb(chip, meter_urb,
 			sizeof(meter_urb));
 		kcontrol->private_value = 0;

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/revert-alsa-usb-audio-purge-needless-variable-length-array.patch queue-4.11/alsa-hda-apply-stac_9200_dell_m22-quirk-for-dell-latitude-d430.patch queue-4.11/alsa-hda-no-loopback-on-alc299-codec.patch queue-4.11/alsa-usb-fix-a-typo-in-tascam-us-16x08-mixer-element.patch