Messages in this thread | | | Subject | Re: [RFC PATCH untested] vhost: block speculation of translated descriptors | From | Jason Wang <> | Date | Tue, 10 Sep 2019 09:52:10 +0800 |
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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>
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