From c08eadca1bdfa099e20a32f8fa4b52b2f672236d Mon Sep 17 00:00:00 2001
From: Dongliang Mu <mudongliangabcd@gmail.com>
Date: Sat, 22 Jan 2022 15:44:59 +0800
Subject: [PATCH] media: em28xx: initialize refcount before kref_get
Git-commit: c08eadca1bdfa099e20a32f8fa4b52b2f672236d
Patch-mainline: v5.18-rc1
References: CVE-2022-3239 bsc#1203552
The commit 47677e51e2a4("[media] em28xx: Only deallocate struct
em28xx after finishing all extensions") adds kref_get to many init
functions (e.g., em28xx_audio_init). However, kref_init is called too
late in em28xx_usb_probe, since em28xx_init_dev before will invoke
those init functions and call kref_get function. Then refcount bug
occurs in my local syzkaller instance.
Fix it by moving kref_init before em28xx_init_dev. This issue occurs
not only in dev but also dev->dev_next.
Fixes: 47677e51e2a4 ("[media] em28xx: Only deallocate struct em28xx after finishing all extensions")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/media/usb/em28xx/em28xx-cards.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -3651,6 +3651,8 @@ static int em28xx_usb_probe(struct usb_i
goto err_free;
}
+ kref_init(&dev->ref);
+
dev->devno = nr;
dev->model = id->driver_info;
dev->alt = -1;
@@ -3737,8 +3739,6 @@ static int em28xx_usb_probe(struct usb_i
dev->dvb_xfer_bulk ? "bulk" : "isoc");
}
- kref_init(&dev->ref);
-
request_modules(dev);
/*