From 09f1652f36c5c4e8a6a640ce887f9ea0f48a7958 Mon Sep 17 00:00:00 2001
From: dan <Dan Kennedy>
Date: Thu, 7 Sep 2023 13:53:09 +0000
Subject: [PATCH] Fix a buffer overread in the sessions extension that could
 occur when processing a corrupt changeset.

FossilOrigin-Name: 0e4e7a05c4204b47a324d67e18e76d2a98e26b2723d19d5c655ec9fd2e41f4b7

diff --git a/ext/session/sqlite3session.c b/ext/session/sqlite3session.c
index 9f862f2465..0491549231 100644
--- a/ext/session/sqlite3session.c
+++ b/ext/session/sqlite3session.c
@@ -2811,15 +2811,19 @@ static int sessionReadRecord(
         }
       }
       if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
-        sqlite3_int64 v = sessionGetI64(aVal);
-        if( eType==SQLITE_INTEGER ){
-          sqlite3VdbeMemSetInt64(apOut[i], v);
+        if( (pIn->nData-pIn->iNext)<8 ){
+          rc = SQLITE_CORRUPT_BKPT;
         }else{
-          double d;
-          memcpy(&d, &v, 8);
-          sqlite3VdbeMemSetDouble(apOut[i], d);
+          sqlite3_int64 v = sessionGetI64(aVal);
+          if( eType==SQLITE_INTEGER ){
+            sqlite3VdbeMemSetInt64(apOut[i], v);
+          }else{
+            double d;
+            memcpy(&d, &v, 8);
+            sqlite3VdbeMemSetDouble(apOut[i], d);
+          }
+          pIn->iNext += 8;
         }
-        pIn->iNext += 8;
       }
     }
   }
-- 
2.43.0