linux-kernel - [PATCH] media: em28xx: fix corrupted list

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Date:   Tue,  6 Jul 2021 17:50:25 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+a6969ef522a36d3344c9@...kaller.appspotmail.com
Subject: [PATCH] media: em28xx: fix corrupted list

Syzbot reported corrupted list in em28xx driver. The problem was in
non-reinitialized lists on disconnect. Since all 2 lists are global
variables and driver can be connected and disconnected many times we
should call INIT_LIST_HEAD() in .disconnect method to prevent corrupted
list entries.

Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
Reported-by: syzbot+a6969ef522a36d3344c9@...kaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---
 drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
 drivers/media/usb/em28xx/em28xx-core.c  | 6 ++++++
 drivers/media/usb/em28xx/em28xx.h       | 1 +
 3 files changed, 9 insertions(+)

diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index ba9292e2a587..8b1ff79c37a0 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -4148,6 +4148,8 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
 		dev->dev_next = NULL;
 	}
 	kref_put(&dev->ref, em28xx_free_device);
+
+	em28xx_reset_lists();
 }
 
 static int em28xx_usb_suspend(struct usb_interface *intf,
diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index 584fa400cd7d..03970ed00dba 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c
@@ -1131,6 +1131,12 @@ void em28xx_init_extension(struct em28xx *dev)
 	mutex_unlock(&em28xx_devlist_mutex);
 }
 
+void em28xx_reset_lists(void)
+{
+	INIT_LIST_HEAD(&em28xx_devlist);
+	INIT_LIST_HEAD(&em28xx_extension_devlist);
+}
+
 void em28xx_close_extension(struct em28xx *dev)
 {
 	const struct em28xx_ops *ops = NULL;
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index ab167cd1f400..73caaaa398d3 100644
--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -835,6 +835,7 @@ void em28xx_stop_urbs(struct em28xx *dev);
 int em28xx_set_mode(struct em28xx *dev, enum em28xx_mode set_mode);
 int em28xx_gpio_set(struct em28xx *dev, const struct em28xx_reg_seq *gpio);
 int em28xx_register_extension(struct em28xx_ops *dev);
+void em28xx_reset_lists(void);
 void em28xx_unregister_extension(struct em28xx_ops *dev);
 void em28xx_init_extension(struct em28xx *dev);
 void em28xx_close_extension(struct em28xx *dev);
-- 
2.32.0