Re: [PATCH v8 1/7] vhost-user: Add VirtIO Shared Memory map request

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Sep 10, 2025 at 01:54:14PM +0200, Albert Esteve wrote:
> +static int
> +vhost_user_backend_handle_shmem_map(struct vhost_dev *dev,
> +                                    QIOChannel *ioc,
> +                                    VhostUserHeader *hdr,
> +                                    VhostUserPayload *payload,
> +                                    int fd)
> +{
> +    VirtioSharedMemory *shmem;
> +    VhostUserMMap *vu_mmap = &payload->mmap;
> +    Error *local_err = NULL;
> +    g_autoptr(GString) shm_name = g_string_new(NULL);
> +
> +    if (fd < 0) {
> +        error_report("Bad fd for map");
> +        return -EBADF;
> +    }
> +
> +    if (QSIMPLEQ_EMPTY(&dev->vdev->shmem_list)) {
> +        error_report("Device has no VIRTIO Shared Memory Regions. "
> +                     "Requested ID: %d", vu_mmap->shmid);
> +        return -EFAULT;
> +    }
> +
> +    shmem = virtio_find_shmem_region(dev->vdev, vu_mmap->shmid);
> +    if (!shmem) {
> +        error_report("VIRTIO Shared Memory Region at "
> +                     "ID %d not found or unitialized", vu_mmap->shmid);
> +        return -EFAULT;
> +    }
> +
> +    if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len ||
> +        (vu_mmap->shm_offset + vu_mmap->len) > shmem->mr.size) {
> +        error_report("Bad offset/len for mmap %" PRIx64 "+%" PRIx64,
> +                     vu_mmap->shm_offset, vu_mmap->len);
> +        return -EFAULT;
> +    }
> +
> +    g_string_printf(shm_name, "virtio-shm%i-%lu",
> +                    vu_mmap->shmid, vu_mmap->shm_offset);
> +
> +    memory_region_transaction_begin();
> +
> +    /* Create VirtioSharedMemoryMapping object */
> +    VirtioSharedMemoryMapping *mapping = virtio_shared_memory_mapping_new(
> +        vu_mmap->shmid, fd, vu_mmap->fd_offset, vu_mmap->shm_offset,
> +        vu_mmap->len, vu_mmap->flags & VHOST_USER_FLAG_MAP_RW);
> +
> +    if (!mapping) {
> +        memory_region_transaction_commit();
> +        return -EFAULT;
> +    }
> +
> +    /* Add the mapping to the shared memory region */
> +    if (virtio_add_shmem_map(shmem, mapping) != 0) {

Missing check for overlap with existing mappings. The spec does not
allow overlap.

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