From 1565241343f00b203ee86810694d42992336b7f4 Mon Sep 17 00:00:00 2001
From: tbeu <tbeu@users.noreply.github.com>
Date: Sun, 10 Mar 2024 20:21:00 +0100
Subject: [PATCH] Fix bad argument for H5S_get_simple_extent_dims

As reported by https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=66627
---
 src/mat73.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/mat73.c b/src/mat73.c
index a042d73c..b5333667 100644
--- a/src/mat73.c
+++ b/src/mat73.c
@@ -623,18 +623,20 @@ Mat_H5ReadFieldNames(matvar_t *matvar, hid_t dset_id, hsize_t *nfields)
     hsize_t i;
     hid_t attr_id, space_id;
     herr_t herr;
-    int err;
+    int err, ndims;
 
     attr_id = H5Aopen_by_name(dset_id, ".", "MATLAB_fields", H5P_DEFAULT, H5P_DEFAULT);
     space_id = H5Aget_space(attr_id);
-    err = H5Sget_simple_extent_dims(space_id, nfields, NULL);
-    if ( err < 0 ) {
+    ndims = H5Sget_simple_extent_ndims(space_id);
+    if ( 0 > ndims || 1 < ndims ) {
+        *nfields = 0;
         H5Sclose(space_id);
         H5Aclose(attr_id);
         return MATIO_E_GENERIC_READ_ERROR;
     } else {
         err = MATIO_E_NO_ERROR;
     }
+    (void)H5Sget_simple_extent_dims(space_id, nfields, NULL);
     if ( *nfields > 0 ) {
         hid_t field_id;
         hvl_t *fieldnames_vl = (hvl_t *)calloc((size_t)(*nfields), sizeof(*fieldnames_vl));