linux-kernel - [PATCH 1/2] media: em28xx-video: add the unregister of video/VBI entity

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Message-ID: <tencent_0D8C88E7C506C4D2C2064149816ECB6EDB06@qq.com>
Date: Sun, 11 Jan 2026 13:29:10 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+16062f26c6480975e5ed@...kaller.appspotmail.com
Cc: laurent.pinchart@...asonboard.com,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	mchehab@...nel.org,
	sakari.ailus@...ux.intel.com,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH 1/2] media: em28xx-video: add the unregister of video/VBI entity

When creating a media graph, a failure occurred due to the lack of
a corresponding decoder. During the subsequent media device release
process, the video and VBI devices were not properly unregistered,
leading to a use-after-free vulnerability reported by syzbot [1].

The fix involves adding the necessary unregister operations.

[1]
BUG: KASAN: slab-use-after-free in media_device_unregister+0x141/0x430 drivers/media/mc/mc-device.c:804
Read of size 8 at addr ffff88807c114210 by task kworker/1:9/6093
Call Trace:
 media_device_unregister+0x141/0x430 drivers/media/mc/mc-device.c:804
 em28xx_unregister_media_device drivers/media/usb/em28xx/em28xx-cards.c:3511 [inline]
 em28xx_release_resources+0xac/0x240 drivers/media/usb/em28xx/em28xx-cards.c:3532
 em28xx_usb_disconnect+0x19f/0x2f0 drivers/media/usb/em28xx/em28xx-cards.c:4201
 usb_unbind_interface+0x26e/0x910 drivers/usb/core/driver.c:458
 
Allocated by task 5932:
 em28xx_v4l2_init+0x10b/0x2e70 drivers/media/usb/em28xx/em28xx-video.c:2532
 em28xx_init_extension+0x120/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1117
 
Freed by task 5932:
 em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2118 [inline]
 kref_put include/linux/kref.h:65 [inline]
 em28xx_v4l2_init+0x1683/0x2e70 drivers/media/usb/em28xx/em28xx-video.c:2901
 
Reported-by: syzbot+16062f26c6480975e5ed@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=16062f26c6480975e5ed
Tested-by: syzbot+16062f26c6480975e5ed@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 drivers/media/usb/em28xx/em28xx-video.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
index 2dfa3242a7ab..45b68ebf2e9c 100644
--- a/drivers/media/usb/em28xx/em28xx-video.c
+++ b/drivers/media/usb/em28xx/em28xx-video.c
@@ -882,9 +882,12 @@ static void em28xx_v4l2_media_release(struct em28xx *dev)
 
 	for (i = 0; i < MAX_EM28XX_INPUT; i++) {
 		if (!INPUT(i)->type)
-			return;
+			break;
 		media_device_unregister_entity(&dev->input_ent[i]);
 	}
+	media_device_unregister_entity(&dev->v4l2->vdev.entity);
+	if (em28xx_vbi_supported(dev))
+		media_device_unregister_entity(&dev->v4l2->vbi_dev.entity);
 #endif
 }
 
-- 
2.43.0