linux-kernel - [PATCH next 2/2] sound: usb: fix use after free in usb_audio

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Message-Id: <16da19126ff461e5e64a9aec648cce28fb8ed73e.1615242183.git.paskripkin@gmail.com>
Date:   Tue,  9 Mar 2021 01:30:57 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     perex@...ex.cz, tiwai@...e.com, kai.heng.feng@...onical.com
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>
Subject: [PATCH next 2/2] sound: usb: fix use after free in usb_audio_disconnect

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>
---
 sound/usb/card.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 3fd1743513b5..b6f4c0848e66 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -907,6 +907,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 		}
 	}
 
+	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;
@@ -915,9 +918,6 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 	} 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 */
-- 
2.25.1