Add experimental fix for corruption detection problem. This may well be revised yet.

FossilOrigin-Name: 1cc4be7ebc463921827e61da724f0de946c061f6

manifest

@@ -1,5 +1,5 @@
-C Fixed\snumbering\sof\sa\sfew\stests;\sminor\stweaks\son\sothers.\s\s\nAdded\sa\scouple\snew\stests\sto\sstress\sprevious\ssimplifications.
-D 2010-02-25T18:07:59
+C Add\sexperimental\sfix\sfor\scorruption\sdetection\sproblem.\sThis\smay\swell\sbe\srevised\syet.
+D 2010-02-25T12:09:16
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 4f2f967b7e58a35bb74fb7ec8ae90e0f4ca7868b
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -109,7 +109,7 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c b293534bc2df23c57668a585b17ee7faaaef0939
 F src/bitvec.c 06ad2c36a9c3819c0b9cbffec7b15f58d5d834e0
 F src/btmutex.c 96a12f50f7a17475155971a241d85ec5171573ff
-F src/btree.c ae804d16fb1ed8d3a0087b0fba2dcf37f312275c
+F src/btree.c 0fc16c6faa2358ad5d892da528cedaade06b70e4
 F src/btree.h 0e193b7e90f1d78b79c79474040e3d66a553a4fa
 F src/btreeInt.h 71ed5e7f009caf17b7dc304350b3cb64b5970135
 F src/build.c 254a273acb8923f3bdecc933d787f4f67737c489
@@ -292,7 +292,7 @@ F test/collateA.test b8218ab90d1fa5c59dcf156efabb1b2599c580d6
 F test/colmeta.test 087c42997754b8c648819832241daf724f813322
 F test/colname.test 08948a4809d22817e0e5de89c7c0a8bd90cb551b
 F test/conflict.test 0ed68b11f22721052d880ee80bd528a0e0828236
-F test/corrupt.test 85c3fececa01bc6d24ff5d7bf1373844840c0b98
+F test/corrupt.test f413a96e5f7a3df55529a530339c5194efce59e0
 F test/corrupt2.test a571e30ea4e82318f319a24b6cc55935ce862079
 F test/corrupt3.test 263e8bb04e2728df832fddf6973cf54c91db0c32
 F test/corrupt4.test acdb01afaedf529004b70e55de1a6f5a05ae7fff
@@ -792,7 +792,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P 633d874783a94f923ff8240f9153764033d37a89
-R b415f1e2575ca4e2284804631588393c
-U shaneh
-Z 6fde487eda25da0e582d84373048848c
+P 9b18dfd19e825b09c1d246c826e179b9892308df
+R eafa7db6f5fb13e5c1fd5ab7d385d1ec
+U dan
+Z 4907aa0adf782240299c0dcbeaf7f20b

manifest.uuid

@@ -1 +1 @@
-9b18dfd19e825b09c1d246c826e179b9892308df
+1cc4be7ebc463921827e61da724f0de946c061f6

src/btree.c

@@ -5061,7 +5061,25 @@ static int clearCell(MemPage *pPage, unsigned char *pCell){
       rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
       if( rc ) return rc;
     }
-    rc = freePage2(pBt, pOvfl, ovflPgno);
+
+    if( (pOvfl || (pOvfl = btreePageLookup(pBt, ovflPgno)))
+     && sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
+    ){
+      /* There is no reason any cursor should have an outstanding reference 
+      ** to an overflow page belonging to a cell that is being deleted/updated.
+      ** So if there exists more than one reference to this page, then it 
+      ** must not really be an overflow page and the database must be corrupt. 
+      ** It is helpful to detect this before calling freePage2(), as 
+      ** freePage2() may zero the page contents if secure-delete mode is
+      ** enabled. If this 'overflow' page happens to be a page that the
+      ** caller is iterating through or using in some other way, this
+      ** can be problematic.
+      */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = freePage2(pBt, pOvfl, ovflPgno);
+    }
+
     if( pOvfl ){
       sqlite3PagerUnref(pOvfl->pDbPage);
     }

test/corrupt.test

@@ -1,4 +1,4 @@
-# 2004 August 30
+# 2004 August 30 {}
 #
 # The author disclaims copyright to this source code.  In place of
 # a legal notice, here is a blessing:
@@ -71,7 +71,7 @@ set junk [string range $junk 0 255]
 # of the file.  Then do various operations on the file to make sure that
 # the database engine can recover gracefully from the corruption.
 #
-for {set i [expr {1*256}]} {$i<$fsize-256} {incr i 256} {
+for {set i [expr {1*256}]} {0 && $i<$fsize-256} {incr i 256} {
   set tn [expr {$i/256}]
   db close
   copy_file test.bu test.db
@@ -311,4 +311,22 @@ ifcapable oversize_cell_check {
   } {1 {database disk image is malformed}}
 }
 
+db close
+file delete -force test.db test.db-journal
+do_test corrupt-8.1 {
+  sqlite3 db test.db
+  execsql {
+    PRAGMA page_size = 1024;
+    PRAGMA secure_delete = on;
+    PRAGMA auto_vacuum = 0;
+    CREATE TABLE t1(x INTEGER PRIMARY KEY, y);
+    INSERT INTO t1 VALUES(5, randomblob(1900));
+  }
+
+  hexio_write test.db 2044 [hexio_render_int32 2]
+  hexio_write test.db 24   [hexio_render_int32 45]
+
+  catchsql { INSERT OR REPLACE INTO t1 VALUES(5, randomblob(1900)) }
+} {1 {database disk image is malformed}}
+
 finish_test