On 10/23/21 3:11 PM, Michael S. Tsirkin wrote: > On Fri, Oct 22, 2021 at 01:17:26PM -0500, michael.christie@xxxxxxxxxx wrote: >> On 10/22/21 11:12 AM, michael.christie@xxxxxxxxxx wrote: >>> On 10/22/21 5:47 AM, Michael S. Tsirkin wrote: >>>>> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h >>>>> index c998860d7bbc..e5c0669430e5 100644 >>>>> --- a/include/uapi/linux/vhost.h >>>>> +++ b/include/uapi/linux/vhost.h >>>>> @@ -70,6 +70,17 @@ >>>>> #define VHOST_VRING_BIG_ENDIAN 1 >>>>> #define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct vhost_vring_state) >>>>> #define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct vhost_vring_state) >>>>> +/* By default, a device gets one vhost_worker created during VHOST_SET_OWNER >>>>> + * that its virtqueues share. This allows userspace to create a vhost_worker >>>>> + * and map a virtqueue to it or map a virtqueue to an existing worker. >>>>> + * >>>>> + * If pid > 0 and it matches an existing vhost_worker thread it will be bound >>>>> + * to the vq. If pid is VHOST_VRING_NEW_WORKER, then a new worker will be >>>>> + * created and bound to the vq. >>>>> + * >>>>> + * This must be called after VHOST_SET_OWNER and before the vq is active. >>>>> + */ >>>> >>>> A couple of things here: >>>> it's probably a good idea not to make it match pid exactly, >>>> if for no other reason than I'm not sure we want to >>>> commit this being a pid. Let's just call it an id? >>> >>> Ok. >>> >>>> And maybe byteswap it or xor with some value >>>> just to make sure userspace does not begin abusing it anyway. >>>> >>>> Also, interaction with pid namespace is unclear to me. >>>> Can you document what happens here? >>> >>> This current patchset only allows the vhost_dev owner to >>> create/bind workers for devices it owns, so namespace don't come >> >> I made a mistake here. The patches do restrict VHOST_SET_VRING_WORKER >> to the same owner like I wrote. However, it looks like we could have 2 >> threads with the same mm pointer so vhost_dev_check_owner returns true, >> but they could be in different namespaces. >> >> Even though we are not going to pass the pid_t between user/kernel >> space, should I add a pid namespace check when I repost the patches? > > Um it's part of the ioctl. How you are not going to pass it around? The not passing a pid around was referring to your comment about obfuscating the pid. I might have misunderstood you and thought you wanted to do something more like you suggested below where to userspace it's just some int as far as userspace knows. > > So if we do worry about this, I would just make it a 64 bit integer, > rename it "id" and increment each time a thread is created. > Yeah, this works for me. I just used a ida to allocate the id. We can then use it's lookup functions too.
