Received-SPF: pass (google.com: domain of linux-kernel+bounces-89615-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
From: Hillf Danton <hdanton@sina.com>
To: syzbot <syzbot+b2391895514ed9ef4a8e@syzkaller.appspotmail.com>
Cc: linux-kernel@vger.kernel.org,
	syzkaller-bugs@googlegroups.com
Subject: Re: KASAN: use-after-free Read in v4l2_fh_open
Date: Sun,  3 Mar 2024 07:07:02 +0800
Message-Id: <20240302230702.1207-1-hdanton@sina.com>
In-Reply-To: <00000000000017937c05bb617f1d@google.com>
References: 
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

On Mon, 15 Feb 2021 07:18:22 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    291009f6 Merge tag 'pm-5.11-rc8' of git://git.kernel.org/p..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17179dd4d00000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/drivers/media/usb/em28xx/em28xx-video.c
+++ y/drivers/media/usb/em28xx/em28xx-video.c
@@ -2152,6 +2152,10 @@ static int em28xx_v4l2_open(struct file
 	if (mutex_lock_interruptible(&dev->lock))
 		return -ERESTARTSYS;
 
+	if (!dev->v4l2) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 	ret = v4l2_fh_open(filp);
 	if (ret) {
 		dev_err(&dev->intf->dev,
@@ -2161,6 +2165,7 @@ static int em28xx_v4l2_open(struct file
 		return ret;
 	}
 
+	v4l2 = dev->v4l2;
 	if (v4l2->users == 0) {
 		em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
 
@@ -2899,6 +2904,7 @@ unregister_dev:
 	v4l2_ctrl_handler_free(&v4l2->ctrl_handler);
 	v4l2_device_unregister(&v4l2->v4l2_dev);
 err:
+	video_unregister_device(&v4l2->vdev);
 	dev->v4l2 = NULL;
 	kref_put(&v4l2->ref, em28xx_free_v4l2);
 	mutex_unlock(&dev->lock);
--