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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: Sat,  2 Mar 2024 18:56:11 +0800
Message-Id: <20240302105611.1139-1-hdanton@sina.com>
In-Reply-To: <00000000000017937c05bb617f1d@google.com>
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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);
 
--