allow -1 file descriptor for ioregionfd (#727)

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

1 files changed, 14 insertions, 1 deletions

diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index 5a6269a..94524a2 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -483,7 +483,6 @@ vfu_create_ioeventfd(vfu_ctx_t *vfu_ctx, uint32_t region_idx, int fd,
     vfu_reg_info_t *vfu_reg;
 
     assert(vfu_ctx != NULL);
-    assert(fd >= 0);
 
 #ifndef SHADOW_IOEVENTFD
     if (shadow_fd != -1) {
@@ -542,6 +541,15 @@ free_regions(vfu_ctx_t *vfu_ctx)
  * This function is used to add fd's to the fd return array and gives you back
  * the index of the fd that has been added. If the fd is already present it will
  * return the index to that duplicate fd to reduce the number of fd's sent.
+ * The fd must be a valid fd or -1, any other negative value is not permitted.
+ *
+ * out_fds: an array where the fd is stored
+ * nr_out_fds: pointer to memory that contains the size of the array
+ * fd_search: the fd to add
+ *
+ * returns: the array index where the fd is added to, can be the index of an
+ *  existing fd if this is a duplicate fd. If the fd is -1 then the function
+ *  returns -1.
  */
 static int
 add_fd_index(int *out_fds, size_t *nr_out_fds, int fd_search)
@@ -551,6 +559,11 @@ add_fd_index(int *out_fds, size_t *nr_out_fds, int fd_search)
     assert(out_fds != NULL);
     assert(nr_out_fds != NULL);
 
+    assert(fd_search >= -1);
+    if (fd_search == -1) {
+        return -1;
+    }
+
     for (i = 0; i < *nr_out_fds; i++) {
         if (out_fds[i] == fd_search) {
             return i;