Patch "usb: gadget: u_audio: Fix race condition use of controls after free during gadget unbind." has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    usb: gadget: u_audio: Fix race condition use of controls after free during gadget unbind.

to the 6.6-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:
     usb-gadget-u_audio-fix-race-condition-use-of-control.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 34d6b8ffa32141b046c0c4a67ca2cc2c4d9adb80
Author: Chris Wulff <Chris.Wulff@xxxxxxxxx>
Date:   Thu Apr 25 15:18:01 2024 +0000

    usb: gadget: u_audio: Fix race condition use of controls after free during gadget unbind.
    
    [ Upstream commit 1b739388aa3f8dfb63a9fca777e6dfa6912d0464 ]
    
    Hang on to the control IDs instead of pointers since those are correctly
    handled with locks.
    
    Fixes: 8fe9a03f4331 ("usb: gadget: u_audio: Rate ctl notifies about current srate (0=stopped)")
    Fixes: c565ad07ef35 ("usb: gadget: u_audio: Support multiple sampling rates")
    Fixes: 02de698ca812 ("usb: gadget: u_audio: add bi-directional volume and mute support")
    Signed-off-by: Chris Wulff <chris.wulff@xxxxxxxxx>
    Link: https://lore.kernel.org/stable/CO1PR17MB5419C2BF44D400E4E620C1ADE1172%40CO1PR17MB5419.namprd17.prod.outlook.com
    Link: https://lore.kernel.org/r/CO1PR17MB5419C2BF44D400E4E620C1ADE1172@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index 4a42574b4a7fe..c8e8154c59f50 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -57,13 +57,13 @@ struct uac_rtd_params {
 
   /* Volume/Mute controls and their state */
   int fu_id; /* Feature Unit ID */
-  struct snd_kcontrol *snd_kctl_volume;
-  struct snd_kcontrol *snd_kctl_mute;
+  struct snd_ctl_elem_id snd_kctl_volume_id;
+  struct snd_ctl_elem_id snd_kctl_mute_id;
   s16 volume_min, volume_max, volume_res;
   s16 volume;
   int mute;
 
-	struct snd_kcontrol *snd_kctl_rate; /* read-only current rate */
+	struct snd_ctl_elem_id snd_kctl_rate_id; /* read-only current rate */
 	int srate; /* selected samplerate */
 	int active; /* playback/capture running */
 
@@ -494,14 +494,13 @@ static inline void free_ep_fback(struct uac_rtd_params *prm, struct usb_ep *ep)
 static void set_active(struct uac_rtd_params *prm, bool active)
 {
 	// notifying through the Rate ctrl
-	struct snd_kcontrol *kctl = prm->snd_kctl_rate;
 	unsigned long flags;
 
 	spin_lock_irqsave(&prm->lock, flags);
 	if (prm->active != active) {
 		prm->active = active;
 		snd_ctl_notify(prm->uac->card, SNDRV_CTL_EVENT_MASK_VALUE,
-				&kctl->id);
+				&prm->snd_kctl_rate_id);
 	}
 	spin_unlock_irqrestore(&prm->lock, flags);
 }
@@ -807,7 +806,7 @@ int u_audio_set_volume(struct g_audio *audio_dev, int playback, s16 val)
 
 	if (change)
 		snd_ctl_notify(uac->card, SNDRV_CTL_EVENT_MASK_VALUE,
-				&prm->snd_kctl_volume->id);
+				&prm->snd_kctl_volume_id);
 
 	return 0;
 }
@@ -856,7 +855,7 @@ int u_audio_set_mute(struct g_audio *audio_dev, int playback, int val)
 
 	if (change)
 		snd_ctl_notify(uac->card, SNDRV_CTL_EVENT_MASK_VALUE,
-			       &prm->snd_kctl_mute->id);
+			       &prm->snd_kctl_mute_id);
 
 	return 0;
 }
@@ -1331,7 +1330,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 			err = snd_ctl_add(card, kctl);
 			if (err < 0)
 				goto snd_fail;
-			prm->snd_kctl_mute = kctl;
+			prm->snd_kctl_mute_id = kctl->id;
 			prm->mute = 0;
 		}
 
@@ -1359,7 +1358,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 			err = snd_ctl_add(card, kctl);
 			if (err < 0)
 				goto snd_fail;
-			prm->snd_kctl_volume = kctl;
+			prm->snd_kctl_volume_id = kctl->id;
 			prm->volume = fu->volume_max;
 			prm->volume_max = fu->volume_max;
 			prm->volume_min = fu->volume_min;
@@ -1383,7 +1382,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 		err = snd_ctl_add(card, kctl);
 		if (err < 0)
 			goto snd_fail;
-		prm->snd_kctl_rate = kctl;
+		prm->snd_kctl_rate_id = kctl->id;
 	}
 
 	strscpy(card->driver, card_name, sizeof(card->driver));