Upstream backport: 00ba17479ff31c6825f0e6f28b965f11525e83f6

Fix problem with loading old format of databases exports

diff -ur gdbm-1.18/src/gdbmopen.c gdbm-patch/src/gdbmopen.c

--- gdbm-1.18/src/gdbmopen.c	2018-08-03 10:46:39.000000000 +0200

+++ gdbm-patch/src/gdbmopen.c	2022-07-01 08:56:08.000000000 +0200

@@ -168,9 +168,14 @@

       return GDBM_BLOCK_SIZE_ERROR;

     }

-  if (hdr->next_block != st->st_size)

-    /* FIXME: Should return GDBM_NEED_RECOVERY instead? */

-    return GDBM_BAD_HEADER;

+  /* Technically speaking, the condition below should read

+         hdr->next_block != st->st_size

+     However, gdbm versions prior to commit 4e819c98 could leave

+     hdr->next_block pointing beyond current end of file. To ensure

+     backward compatibility with these versions, the condition has been

+     slackened to this: */

+  if (hdr->next_block < st->st_size)

+     return GDBM_BAD_HEADER;

   /* Make sure dir and dir + dir_size fall within the file boundary */

   if (!(hdr->dir > 0