fail to map segment if DMA region isn't backed by file descriptor

Signed-off-by: Thanos Makatos <thanos.makatos@nutanix.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/dma.h b/lib/dma.h
index e0d6d72..aeed9bb 100644
--- a/lib/dma.h
+++ b/lib/dma.h
@@ -246,9 +246,12 @@ dma_map_sg(dma_controller_t *dma, const dma_sg_t *sg, struct iovec *iov,
         if (sg[i].region >= dma->nregions) {
             return -EINVAL;
         }
+        region = &dma->regions[sg[i].region];
+        if (region->virt_addr == NULL) {
+            return -EFAULT;
+        }
         vfu_log(dma->vfu_ctx, LOG_DEBUG, "map %#lx-%#lx\n",
                sg->dma_addr + sg->offset, sg->dma_addr + sg->offset + sg->length);
-        region = &dma->regions[sg[i].region];
         iov[i].iov_base = region->virt_addr + sg[i].offset;
         iov[i].iov_len = sg[i].length;
         region->refcnt++;