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media: em28xx: initialize refcount before kref_get

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[ Upstream commit c08eadca1bdfa099e20a32f8fa4b52b2f672236d ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Dongliang Mu 2022-01-22 15:44:59 +08:00 committed by Greg Kroah-Hartman
parent 1b46f57d51
commit ec8a37b2d9
1 changed files with 4 additions and 4 deletions
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8
drivers/media/usb/em28xx/em28xx-cards.c
View File

@ -3881,6 +3881,8 @@ 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;
@ -3981,6 +3983,8 @@ 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 &&
@ -4035,12 +4039,8 @@ 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);
/*