escape_byte_string() in gfileattribute.c calls strlen (str) without verifying that str is not NULL. This leads to segmentation faults in code such as the following example:

#include <gio/gio.h>

void main ()
{
  GFileInfo *info;

  g_type_init ();
  info = g_file_info_new ();
  g_file_info_set_attribute (info,
    G_FILE_ATTRIBUTE_STANDARD_SYMLINK_TARGET,
    G_FILE_ATTRIBUTE_TYPE_BYTE_STRING, NULL);
  g_file_info_get_attribute_as_string (info,
    G_FILE_ATTRIBUTE_STANDARD_SYMLINK_TARGET);
}