ivshmem: check the value returned by fstat()

The function fstat() may fail, so check its return value.
Acked-by: NLevente Kurusa <lkurusa@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

hw/misc/ivshmem.c

@@ -324,7 +324,11 @@ static int check_shm_size(IVShmemState *s, int fd) {
 
     struct stat buf;
 
-    fstat(fd, &buf);
+    if (fstat(fd, &buf) < 0) {
+        fprintf(stderr, "ivshmem: exiting: fstat on fd %d failed: %s\n",
+                fd, strerror(errno));
+        return -1;
+    }
 
     if (s->ivshmem_size > buf.st_size) {
         fprintf(stderr,