Messages in this thread | | | Subject | Re: [PATCH] s390: cio: fix two use-after-free bugs in device.c | From | Qinglang Miao <> | Date | Tue, 1 Dec 2020 14:31:52 +0800 |
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在 2020/11/20 15:55, Cornelia Huck 写道: > On Fri, 20 Nov 2020 15:48:49 +0800 > Qinglang Miao <miaoqinglang@huawei.com> 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@huawei.com> >> Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com> >> --- >> 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@huawei.com/
Thanks! > >> } >> ccw_device_set_timeout(cdev, 0); >> cdev->drv = NULL; > > . >
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