Re: [PATCH v9 13/17] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap()

[Jason Wang]

在 2021/7/14 下午5:57, Dan Carpenter 写道:
> On Wed, Jul 14, 2021 at 05:41:54PM +0800, Jason Wang wrote:
> > 在 2021/7/14 下午4:05, Dan Carpenter 写道:
> > > On Wed, Jul 14, 2021 at 10:14:32AM +0800, Jason Wang wrote:
> > > > 在 2021/7/13 下午7:31, Dan Carpenter 写道:
> > > > > On Tue, Jul 13, 2021 at 04:46:52PM +0800, Xie Yongji wrote:
> > > > > > @@ -613,37 +618,28 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v, u64 iova, u64 size)
> > > > > >     	}
> > > > > >     }
> > > > > > -static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> > > > > > -					   struct vhost_iotlb_msg *msg)
> > > > > > +static int vhost_vdpa_pa_map(struct vhost_vdpa *v,
> > > > > > +			     u64 iova, u64 size, u64 uaddr, u32 perm)
> > > > > >     {
> > > > > >     	struct vhost_dev *dev = &v->vdev;
> > > > > > -	struct vhost_iotlb *iotlb = dev->iotlb;
> > > > > >     	struct page **page_list;
> > > > > >     	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
> > > > > >     	unsigned int gup_flags = FOLL_LONGTERM;
> > > > > >     	unsigned long npages, cur_base, map_pfn, last_pfn = 0;
> > > > > >     	unsigned long lock_limit, sz2pin, nchunks, i;
> > > > > > -	u64 iova = msg->iova;
> > > > > > +	u64 start = iova;
> > > > > >     	long pinned;
> > > > > >     	int ret = 0;
> > > > > > -	if (msg->iova < v->range.first ||
> > > > > > -	    msg->iova + msg->size - 1 > v->range.last)
> > > > > > -		return -EINVAL;
> > > > > This is not related to your patch, but can the "msg->iova + msg->size"
> > > > > addition can have an integer overflow.  From looking at the callers it
> > > > > seems like it can.  msg comes from:
> > > > >      vhost_chr_write_iter()
> > > > >      --> dev->msg_handler(dev, &msg);
> > > > >          --> vhost_vdpa_process_iotlb_msg()
> > > > >             --> vhost_vdpa_process_iotlb_update()
> > > > Yes.
> > > >
> > > >
> > > > > If I'm thinking of the right thing then these are allowed to overflow to
> > > > > 0 because of the " - 1" but not further than that.  I believe the check
> > > > > needs to be something like:
> > > > >
> > > > > 	if (msg->iova < v->range.first ||
> > > > > 	    msg->iova - 1 > U64_MAX - msg->size ||
> > > > I guess we don't need - 1 here?
> > > The - 1 is important.  The highest address is 0xffffffff.  So it goes
> > > start + size = 0 and then start + size - 1 == 0xffffffff.
> >
> > Right, so actually
> >
> > msg->iova = 0xfffffffe, msg->size=2 is valid.
> I believe so, yes.  It's inclusive of 0xfffffffe and 0xffffffff.
> (Not an expert).


I think so, and we probably need to fix vhost_overflow() as well which did:

static bool vhost_overflow(u64 uaddr, u64 size)
{
        /* Make sure 64 bit math will not overflow. */
        return uaddr > ULONG_MAX || size > ULONG_MAX || uaddr > 
ULONG_MAX - size;
}

Thanks


> regards,
> dan carpenter