在 2020/11/20 15:55, Cornelia Huck 写道:
On Fri, 20 Nov 2020 15:48:49 +0800
Qinglang Miao <miaoqinglang@xxxxxxxxxx> wrote:
put_device calls release function which do kfree() inside.
So following use of sch&cdev would cause use-after-free bugs.
Fix these by simply adjusting the position of put_device.
Fixes: 37db8985b211 ("s390/cio: add basic protected virtualization support")
Fixes: 74bd0d859dc3 ("s390/cio: fix unlocked access of online member")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Qinglang Miao <miaoqinglang@xxxxxxxxxx>
---
drivers/s390/cio/device.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index b29fe8d50..69492417b 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1664,10 +1664,10 @@ void __init ccw_device_destroy_console(struct ccw_device *cdev)
struct io_subchannel_private *io_priv = to_io_private(sch);
set_io_private(sch, NULL);
- put_device(&sch->dev);
- put_device(&cdev->dev);
dma_free_coherent(&sch->dev, sizeof(*io_priv->dma_area),
io_priv->dma_area, io_priv->dma_area_dma);
+ put_device(&sch->dev);
+ put_device(&cdev->dev);
That change looks reasonable.
kfree(io_priv);
}
@@ -1774,8 +1774,8 @@ static int ccw_device_remove(struct device *dev)
ret, cdev->private->dev_id.ssid,
cdev->private->dev_id.devno);
/* Give up reference obtained in ccw_device_set_online(). */
- put_device(&cdev->dev);
spin_lock_irq(cdev->ccwlock);
+ put_device(&cdev->dev);
As the comment above states, the put_device() gives up the reference
obtained in ccw_device_set_online(). There's at least one more
reference remaining (held by the caller of the remove function). Moving
the put_device() does not fix anything here.
Hi, Cornelia
Sorry for the delayed reply.
Your suggestion is reasonable, there is a mistake in this patch for I
didn't notice that there would be at least one more reference remaining.
So I sent a new patch only to move put_device after dma_free_coherent. I
put the link as below:
https://lore.kernel.org/lkml/20201201063150.82128-1-miaoqinglang@xxxxxxxxxx/
Thanks!
}
ccw_device_set_timeout(cdev, 0);
cdev->drv = NULL;
.
