fix issue with get_region_io_fds when fd = -1 (#606)

An unmappable region should still allow io fds, as they are orthogonal.

Co-authored-by: John Levon <john.levon@nutanix.com>
Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@nutanix.com>

2 files changed, 22 insertions, 7 deletions

diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index 8881dc7..69aeb36 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -558,7 +558,7 @@ handle_device_get_region_io_fds(vfu_ctx_t *vfu_ctx, vfu_msg_t *msg)
     assert(msg != NULL);
     assert(msg->out_fds == NULL);
 
-    if (msg->in_size != sizeof(vfio_user_region_io_fds_request_t)) {
+    if (msg->in_size < sizeof(vfio_user_region_io_fds_request_t)) {
         return ERROR_INT(EINVAL);
     }
 
@@ -576,10 +576,6 @@ handle_device_get_region_io_fds(vfu_ctx_t *vfu_ctx, vfu_msg_t *msg)
 
     vfu_reg = &vfu_ctx->reg_info[req->index];
 
-    if (vfu_reg->fd == -1) {
-        return ERROR_INT(EINVAL);
-    }
-
     LIST_FOREACH(sub_reg, &vfu_reg->subregions, entry) {
         nr_sub_reg++;
     }
diff --git a/test/py/test_device_get_region_io_fds.py b/test/py/test_device_get_region_io_fds.py
index ab29dbb..63e3236 100644
--- a/test/py/test_device_get_region_io_fds.py
+++ b/test/py/test_device_get_region_io_fds.py
@@ -66,6 +66,10 @@ def test_device_get_region_io_fds_setup():
                            mmap_areas=mmap_areas, fd=f.fileno(), offset=0x8000)
     assert ret == 0
 
+    ret = vfu_setup_region(ctx, index=VFU_PCI_DEV_BAR5_REGION_IDX, size=0x8000,
+                           flags=(VFU_REGION_FLAG_RW), offset=0x8000)
+    assert ret == 0
+
     ret = vfu_realize_ctx(ctx)
     assert ret == 0
 
@@ -115,7 +119,7 @@ def test_device_get_region_io_fds_buffer_too_large():
     msg(ctx, sock, VFIO_USER_DEVICE_GET_REGION_IO_FDS, payload, expect =
         errno.EINVAL)
 
-def test_device_get_region_io_fds_no_regions():
+def test_device_get_region_io_fds_no_fds():
 
     payload = vfio_user_region_io_fds_request(argsz = 512, flags = 0,
                                 index = VFU_PCI_DEV_BAR1_REGION_IDX, count = 0)
@@ -136,7 +140,22 @@ def test_device_get_region_io_fds_no_regions_setup():
                                 index = VFU_PCI_DEV_BAR3_REGION_IDX, count = 0)
 
     ret = msg(ctx, sock, VFIO_USER_DEVICE_GET_REGION_IO_FDS, payload,
-              expect=errno.EINVAL)
+              expect = 0)
+
+def test_device_get_region_io_fds_region_no_mmap():
+
+    payload = vfio_user_region_io_fds_request(argsz = 512, flags = 0,
+                                index = VFU_PCI_DEV_BAR5_REGION_IDX, count = 0)
+
+    ret = msg(ctx, sock, VFIO_USER_DEVICE_GET_REGION_IO_FDS, payload,
+              expect = 0)
+
+    reply, ret = vfio_user_region_io_fds_reply.pop_from_buffer(ret)
+
+    assert reply.argsz == len(vfio_user_region_io_fds_reply())
+    assert reply.count == 0
+    assert reply.flags == 0
+    assert reply.index == VFU_PCI_DEV_BAR5_REGION_IDX
 
 def test_device_get_region_io_fds_region_out_of_range():