From 414660066ee2f1670a9f09a11ab41533015b2f3a Mon Sep 17 00:00:00 2001
From: Ondrej Dubaj <odubaj@redhat.com>
Date: Thu, 2 Jan 2020 15:04:42 +0100
Subject: [PATCH] More improvements to shadow table corruption detection in
 FTS3.

---
 ext/fts3/fts3.c       |  4 ++++
 ext/fts3/fts3Int.h    | 10 ++++++++++
 ext/fts3/fts3_write.c | 14 +++++++++++---
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/ext/fts3/fts3.c b/ext/fts3/fts3.c
index f6fb931..caa742f 100644
--- a/ext/fts3/fts3.c
+++ b/ext/fts3/fts3.c
@@ -1460,6 +1460,10 @@ static int fts3InitVtab(
   fts3DatabasePageSize(&rc, p);
   p->nNodeSize = p->nPgsz-35;
 
+#if defined(SQLITE_DEBUG)||defined(SQLITE_TEST)
+  p->nMergeCount = FTS3_MERGE_COUNT;
+#endif
+
   /* Declare the table schema to SQLite. */
   fts3DeclareVtab(&rc, p);
 
diff --git a/ext/fts3/fts3Int.h b/ext/fts3/fts3Int.h
index 077bad7..12392c0 100644
--- a/ext/fts3/fts3Int.h
+++ b/ext/fts3/fts3Int.h
@@ -287,9 +287,19 @@ struct Fts3Table {
   /* True to disable the incremental doclist optimization. This is controled
   ** by special insert command 'test-no-incr-doclist'.  */
   int bNoIncrDoclist;
+
+  /* Number of segments in a level */
+  int nMergeCount;
 #endif
 };
 
+/* Macro to find the number of segments to merge */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+# define MergeCount(P) ((P)->nMergeCount)
+#else
+# define MergeCount(P) FTS3_MERGE_COUNT
+#endif
+
 /*
 ** When the core wants to read from the virtual table, it creates a
 ** virtual table cursor (an instance of the following structure) using
diff --git a/ext/fts3/fts3_write.c b/ext/fts3/fts3_write.c
index 8fc6589..e4b9640 100644
--- a/ext/fts3/fts3_write.c
+++ b/ext/fts3/fts3_write.c
@@ -1152,7 +1152,7 @@ static int fts3AllocateSegdirIdx(
     ** segment and allocate (newly freed) index 0 at level iLevel. Otherwise,
     ** if iNext is less than FTS3_MERGE_COUNT, allocate index iNext.
     */
-    if( iNext>=FTS3_MERGE_COUNT ){
+    if( iNext>=MergeCount(p) ){
       fts3LogMerge(16, getAbsoluteLevel(p, iLangid, iIndex, iLevel));
       rc = fts3SegmentMerge(p, iLangid, iIndex, iLevel);
       *piIdx = 0;
@@ -4249,6 +4249,10 @@ static int fts3IncrmergeLoad(
       int i;
       int nHeight = (int)aRoot[0];
       NodeWriter *pNode;
+      if( nHeight<1 || nHeight>FTS_MAX_APPENDABLE_HEIGHT ){
+        sqlite3_reset(pSelect);
+        return FTS_CORRUPT_VTAB;
+      }
 
       pWriter->nLeafEst = (int)((iEnd - iStart) + 1)/FTS_MAX_APPENDABLE_HEIGHT;
       pWriter->iStart = iStart;
@@ -4997,7 +5001,7 @@ static int fts3DoIncrmerge(
   const char *zParam              /* Nul-terminated string containing "A,B" */
 ){
   int rc;
-  int nMin = (FTS3_MERGE_COUNT / 2);
+  int nMin = (MergeCount(p) / 2);
   int nMerge = 0;
   const char *z = zParam;
 
@@ -5042,7 +5046,7 @@ static int fts3DoAutoincrmerge(
   int rc = SQLITE_OK;
   sqlite3_stmt *pStmt = 0;
   p->nAutoincrmerge = fts3Getint(&zParam);
-  if( p->nAutoincrmerge==1 || p->nAutoincrmerge>FTS3_MERGE_COUNT ){
+  if( p->nAutoincrmerge==1 || p->nAutoincrmerge>MergeCount(p) ){
     p->nAutoincrmerge = 8;
   }
   if( !p->bHasStat ){
@@ -5326,6 +5330,10 @@ static int fts3SpecialInsert(Fts3Table *p, sqlite3_value *pVal){
   }else if( nVal>21 && 0==sqlite3_strnicmp(zVal, "test-no-incr-doclist=", 21) ){
     p->bNoIncrDoclist = atoi(&zVal[21]);
     rc = SQLITE_OK;
+  }else if( nVal>11 && 0==sqlite3_strnicmp(zVal,"mergecount=",11) ){
+    int v = atoi(&zVal[11]);
+    if( v>=4 && v<=FTS3_MERGE_COUNT && (v&1)==0 ) p->nMergeCount = v;
+    rc = SQLITE_OK;
 #endif
   }else{
     rc = SQLITE_ERROR;
-- 
2.19.1