From 8bbd0cce92be98de9f4f727b8bf66fe26e5831ea Mon Sep 17 00:00:00 2001
From: Alexander Korotkov
Date: Sun, 23 Apr 2023 13:58:25 +0300
Subject: Validate ltree siglen GiST option to be int-aligned

Unaligned siglen could lead to an unaligned access to subsequent key fields.

Backpatch to 13, where opclass options were introduced.

Reported-by: Alexander Lakhin
Bug: 17847
Discussion: https://postgr.es/m/17847-171232970bea406b%40postgresql.org
Reviewed-by: Tom Lane, Pavel Borisov, Alexander Lakhin
Backpatch-through: 13
---
 doc/src/sgml/ltree.sgml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/ltree.sgml b/doc/src/sgml/ltree.sgml
index bb66e33944..00a6ae70da 100644
--- a/doc/src/sgml/ltree.sgml
+++ b/doc/src/sgml/ltree.sgml
@@ -637,7 +637,8 @@ Europe & Russia*@ & !Transportation
      path labels as a bitmap signature.  Its optional integer parameter
      <literal>siglen</literal> determines the
      signature length in bytes.  The default signature length is 8 bytes.
-     Valid values of signature length are between 1 and 2024 bytes.  Longer
+     The length must be a positive multiple of <type>int</type> alignment
+     (4 bytes on most machines)) up to 2024.  Longer
      signatures lead to a more precise search (scanning a smaller fraction of the index and
      fewer heap pages), at the cost of a larger index.
     </para>
-- 
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