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Commit 92f84aa8 authored by Dongliang Mu's avatar Dongliang Mu Committed by Greg Kroah-Hartman
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media: em28xx: initialize refcount before kref_get 



[ Upstream commit c08eadca1bdfa099e20a32f8fa4b52b2f672236d ]

The commit 47677e51("[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: 47677e51 ("[media] em28xx: Only deallocate struct em28xx after finishing all extensions")
Reported-by: default avatarsyzkaller <syzkaller@googlegroups.com>
Signed-off-by: default avatarDongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent c6f09994

drivers/media/usb/em28xx/em28xx-cards.c

+4 −4
Original line number Diff line number Diff line
@@ -3821,6 +3821,8 @@ static int em28xx_usb_probe(struct usb_interface *intf, 
		goto err_free;

	}



	kref_init(&dev->ref);



	dev->devno = nr;

	dev->model = id->driver_info;

	dev->alt   = -1;
@@ -3921,6 +3923,8 @@ static int em28xx_usb_probe(struct usb_interface *intf, 
	}



	if (dev->board.has_dual_ts && em28xx_duplicate_dev(dev) == 0) {

		kref_init(&dev->dev_next->ref);



		dev->dev_next->ts = SECONDARY_TS;

		dev->dev_next->alt   = -1;

		dev->dev_next->is_audio_only = has_vendor_audio &&
@@ -3975,12 +3979,8 @@ static int em28xx_usb_probe(struct usb_interface *intf, 
			em28xx_write_reg(dev, 0x0b, 0x82);

			mdelay(100);

		}



		kref_init(&dev->dev_next->ref);

	}



	kref_init(&dev->ref);



	request_modules(dev);



	/*