Messages in this thread | | | Subject | Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok() | From | Jason Wang <> | Date | Wed, 3 Jun 2020 14:36:46 +0800 |
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On 2020/6/3 下午2:30, Michael S. Tsirkin wrote: > On Wed, Jun 03, 2020 at 02:23:08PM +0800, Jason Wang wrote: >>> BTW now I re-read it I don't understand __vhost_get_user_slow: >>> >>> >>> static void __user *__vhost_get_user_slow(struct vhost_virtqueue *vq, >>> void __user *addr, unsigned int size, >>> int type) >>> { >>> int ret; >>> >>> ret = translate_desc(vq, (u64)(uintptr_t)addr, size, vq->iotlb_iov, >>> ARRAY_SIZE(vq->iotlb_iov), >>> VHOST_ACCESS_RO); >>> >>> .. >>> } >>> >>> how does this work? how can we cast a pointer to guest address without >>> adding any offsets? >> >> I'm not sure I get you here. What kind of offset did you mean? >> >> Thanks > OK so points: > > 1. type argument seems unused. Right?
Yes, we can remove that.
> 2. Second argument to translate_desc is a GPA, isn't it?
No, it's IOVA, this function will be called only when IOTLB is enabled.
Thanks
> Here we cast a userspace address to this type. What if it > matches a valid GPA by mistake? >
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