linux-kernel - [PATCH 5.11 175/306] ALSA: usb-audio: fix use after free in usb_audio

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Message-Id: <20210315135513.530255442@linuxfoundation.org>
Date:   Mon, 15 Mar 2021 14:53:58 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pavel Skripkin <paskripkin@...il.com>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 5.11 175/306] ALSA: usb-audio: fix use after free in usb_audio_disconnect

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Pavel Skripkin <paskripkin@...il.com>

commit c5aa956eaeb05fe87e33433d7fd9f5e4d23c7416 upstream.

The problem was in wrong "if" placement. chip->quirk_type is freed
in snd_card_free_when_closed(), but inside if statement it's accesed.

Fixes: 9799110825db ("ALSA: usb-audio: Disable USB autosuspend properly in setup_disable_autosuspend()")
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
Cc: <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/16da19126ff461e5e64a9aec648cce28fb8ed73e.1615242183.git.paskripkin@gmail.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 sound/usb/card.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -908,6 +908,9 @@ static void usb_audio_disconnect(struct
 		}
 	}
 
+	if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND)
+		usb_enable_autosuspend(interface_to_usbdev(intf));
+
 	chip->num_interfaces--;
 	if (chip->num_interfaces <= 0) {
 		usb_chip[chip->index] = NULL;
@@ -916,9 +919,6 @@ static void usb_audio_disconnect(struct
 	} else {
 		mutex_unlock(&register_mutex);
 	}
-
-	if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND)
-		usb_enable_autosuspend(interface_to_usbdev(intf));
 }
 
 /* lock the shutdown (disconnect) task and autoresume */