Fix potential buffer overwrite that could occur in fts5 when processing corrupt records.

FossilOrigin-Name: 4a5ad516ea93926c0d5206b4d72c3675905d2bf666b27a649256b93eb95c671b

ext/fts5/fts5_index.c

@@ -922,7 +922,7 @@ static void fts5DataRelease(Fts5Data *pData){
 static Fts5Data *fts5LeafRead(Fts5Index *p, i64 iRowid){
   Fts5Data *pRet = fts5DataRead(p, iRowid);
   if( pRet ){
-    if( pRet->nn<4 || pRet->szLeaf>pRet->nn ){
+    if( pRet->szLeaf<4 || pRet->szLeaf>pRet->nn ){
       FTS5_CORRUPT_ROWID(p, iRowid);
       fts5DataRelease(pRet);
       pRet = 0;

ext/fts5/test/fts5corruptA.test

@@ -0,0 +1,72 @@
+# 2026 May 11
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+
+source [file join [file dirname [info script]] fts5_common.tcl]
+set testprefix fts5corruptA
+
+# If SQLITE_ENABLE_FTS5 is not defined, omit this file.
+ifcapable !fts5 {
+  finish_test
+  return
+}
+sqlite3_fts5_may_be_corrupt 1
+
+do_execsql_test 1.0 {
+  CREATE VIRTUAL TABLE t USING fts5(x, detail='full');
+  INSERT INTO t(t, rank) VALUES('pgsz', 32);
+}
+
+set big [string repeat "a " 200]
+do_execsql_test 1.1 {
+  INSERT INTO t(rowid, x) VALUES(1, $big)
+}
+
+do_test 1.2 {
+  db eval { 
+      SELECT min(rowid) AS base_rowid, count(*) AS page_count FROM t_data
+      WHERE rowid>1000
+  } {}
+} {}
+
+do_test 1.3 {
+  for {set ii 0} {$ii < 5} {incr ii} {
+    db eval { 
+      INSERT INTO t_data(rowid, block) 
+      VALUES( $base_rowid + $page_count + $ii, zeroblob(4) );
+    }
+  }
+  db eval { 
+    INSERT INTO t_data(rowid, block) 
+      VALUES( $base_rowid + $page_count + 5, 
+      unhex('00000080' || 'CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC') );
+  }
+  set {} {}
+} {}
+
+db close
+
+do_test 1.4 {
+  set hex [hexio_read test.db 0 [file size test.db]]
+
+  set off [string first "023061018310" $hex]
+  set hex [string replace $hex $off [expr $off+11] 023061018370]
+  hexio_write test.db 0 $hex
+} {6144}
+
+sqlite3 db test.db
+
+do_catchsql_test 1.5 {
+  SELECT rowid FROM t WHERE t MATCH 'a'
+} {1 {fts5: corruption found reading blob 137438953481 from table "t"}}
+
+sqlite3_fts5_may_be_corrupt 0
+finish_test

manifest

@@ -1,5 +1,5 @@
-C Fix\sharmless\sbug\sin\stesting\slogic.\s\sNo\schanges\sto\sdeliverables.
-D 2026-05-11T11:05:17.268
+C Fix\spotential\sbuffer\soverwrite\sthat\scould\soccur\sin\sfts5\swhen\sprocessing\scorrupt\srecords.
+D 2026-05-11T11:12:06.895
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -113,7 +113,7 @@ F ext/fts5/fts5_buffer.c dcc3f0352339fe79c9d8abbc1c2009bc3469206467880bf43558447
 F ext/fts5/fts5_config.c bfba970fe1e4eed18ee57c8d51458e226db9a960ddf775c5e50e3d76603a667e
 F ext/fts5/fts5_expr.c 71d48e8cf0358deace4949276647d317ff7665db6db09f40b81e2e7fe6664c7c
 F ext/fts5/fts5_hash.c d5871df92ce3fa210a650cf419ee916b87c29977e86084d06612edf772bff6f5
-F ext/fts5/fts5_index.c f8cfa37bb7397e5ede20242e4c9cb030bc8b4584ce3f23a5e2495038c0ae64bd
+F ext/fts5/fts5_index.c 957534376f8ee60d4fd9af5d7d968831abf1c8cac7a6799b90acb5cd3b9ba25a
 F ext/fts5/fts5_main.c b0fed47b3b4420ba6810373480a75bc28a9c0b7d16478d19a396436fb3ff17d7
 F ext/fts5/fts5_storage.c 19bc7c4cbe1e6a2dd9849ef7d84b5ca1fcbf194cefc3e386b901e00e08bf05c2
 F ext/fts5/fts5_tcl.c 2be6cc14f9448f720fd4418339cd202961a0801ea9424cb3d9de946f8f5a051c
@@ -169,6 +169,7 @@ F ext/fts5/test/fts5corrupt6.test 2d72db743db7b5d9c9a6d0cfef24d799ed1aa5e8192b66
 F ext/fts5/test/fts5corrupt7.test 814aab492d7a09abb5bfdd81cc66fc206d7f3868f9a3bae91876e02efc466fb3
 F ext/fts5/test/fts5corrupt8.test 0b10750caf8aa23fa1c379ca4caf6130d41454505e4d5315590f4061eedcbe44
 F ext/fts5/test/fts5corrupt9.test 4253b9b59f33effac8b67da72ec34309c738aca2d5e8e2656bfbbd6a489a1dfe
+F ext/fts5/test/fts5corruptA.test 944c40f8da0f5db581ce60d32f82fb0eeb1af4dd8ea3172c207873082a0309a4
 F ext/fts5/test/fts5corruptbig.test 9f95b40fa36e292feceab02b2ef06e21878bfa1ac7afefa138aae05518b51774
 F ext/fts5/test/fts5delete.test 2a5008f8b1174ef41d1974e606928c20e4f9da77d9f8347aed818994d89cced4
 F ext/fts5/test/fts5detail.test 54015e9c43ec4ba542cfb93268abdf280e0300f350efd08ee411284b03595cc4
@@ -2203,8 +2204,8 @@ F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee
 F tool/warnings.sh a554d13f6e5cf3760f041b87939e3d616ec6961859c3245e8ef701d1eafc2ca2
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
 F tool/winmain.c 00c8fb88e365c9017db14c73d3c78af62194d9644feaf60e220ab0f411f3604c
-P 45a215290896eee9776c2b1727363f6e1c1aad5b521f4f92b13981a5da5d0f54
-R 56d8e81cc54933505be73d3c91d90f52
-U drh
-Z 9629b616a8c58068be0a9d9501b3e230
+P c4a6e62b5f36f9df988d2ec12a92a614e9e813cdcd50198ec2827c33745a362a
+R f530d7c8db944db9f53748a1ac21750c
+U dan
+Z 2ea807a6fd2cda207a366790e8ee04ce
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-c4a6e62b5f36f9df988d2ec12a92a614e9e813cdcd50198ec2827c33745a362a
+4a5ad516ea93926c0d5206b4d72c3675905d2bf666b27a649256b93eb95c671b