Messages in this thread | | | Subject | Re: [RFC PATCH untested] vhost: block speculation of translated descriptors | From | Jason Wang <> | Date | Tue, 10 Sep 2019 15:28:27 +0800 |
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On 2019/9/10 下午2:48, Michael S. Tsirkin wrote: > On Tue, Sep 10, 2019 at 09:52:10AM +0800, Jason Wang wrote: >> On 2019/9/9 下午10:45, Michael S. Tsirkin wrote: >>> On Mon, Sep 09, 2019 at 03:19:55PM +0800, Jason Wang wrote: >>>> On 2019/9/8 下午7:05, Michael S. Tsirkin wrote: >>>>> iovec addresses coming from vhost are assumed to be >>>>> pre-validated, but in fact can be speculated to a value >>>>> out of range. >>>>> >>>>> Userspace address are later validated with array_index_nospec so we can >>>>> be sure kernel info does not leak through these addresses, but vhost >>>>> must also not leak userspace info outside the allowed memory table to >>>>> guests. >>>>> >>>>> Following the defence in depth principle, make sure >>>>> the address is not validated out of node range. >>>>> >>>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> >>>>> --- >>>>> drivers/vhost/vhost.c | 4 +++- >>>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >>>>> index 5dc174ac8cac..0ee375fb7145 100644 >>>>> --- a/drivers/vhost/vhost.c >>>>> +++ b/drivers/vhost/vhost.c >>>>> @@ -2072,7 +2072,9 @@ static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len, >>>>> size = node->size - addr + node->start; >>>>> _iov->iov_len = min((u64)len - s, size); >>>>> _iov->iov_base = (void __user *)(unsigned long) >>>>> - (node->userspace_addr + addr - node->start); >>>>> + (node->userspace_addr + >>>>> + array_index_nospec(addr - node->start, >>>>> + node->size)); >>>>> s += size; >>>>> addr += size; >>>>> ++ret; >>>> I've tried this on Kaby Lake smap off metadata acceleration off using >>>> testpmd (virtio-user) + vhost_net. I don't see obvious performance >>>> difference with TX PPS. >>>> >>>> Thanks >>> Should I push this to Linus right now then? It's a security thing so >>> maybe we better do it ASAP ... what's your opinion? >> >> Yes, you can. >> >> Acked-by: Jason Wang <jasowang@redhat.com> > > And should I include > > Tested-by: Jason Wang <jasowang@redhat.com> > > ?
Yes.
Thanks
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