Have the dbstat module arrange things internally so that there are 256 addressable...

FossilOrigin-Name: c4c705abc60624bf9ba4c1c05286b902b965f7ba9fd776c4ef8bc1fb78a4ccde

diff --git a/manifest b/manifest
index 443ef98e8cd567e40230350422cec24c2e5861ea..89af98225feb8ce1d8bd65a38eac66b8298342b7 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sanother\sproblem\swith\sALTER\sTABLE\sand\svector\sUPDATE\sstatements\swithin\striggers.
-D 2021-09-29T18:33:26.405
+C Have\sthe\sdbstat\smodule\sarrange\sthings\sinternally\sso\sthat\sthere\sare\s256\saddressable\sbytes\sfollowing\seach\spage\sbuffer.\sThis\sway,\ssmall\sbuffer\soverreads\scaused\sby\scorrupt\sdatabase\spages\sdo\snot\slead\sto\sundefined\sbehaviour.
+D 2021-09-29T19:15:25.012
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -499,7 +499,7 @@ F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c 8159d5f706551861c18ec6c8f6bdf105e15ea00367f05d9ab65d31a1077facc1
 F src/date.c e0632f335952b32401482d099321bbf12716b29d6e72836b53ae49683ebae4bf
 F src/dbpage.c 8a01e865bf8bc6d7b1844b4314443a6436c07c3efe1d488ed89e81719047833a
-F src/dbstat.c bea044cfe99eab6c527837e196a5335c128989bdb354cf1b4973b85ea561d66b
+F src/dbstat.c 861e08690fcb0f2ee1165eff0060ea8d4f3e2ea10f80dab7d32ad70443a6ff2d
 F src/delete.c 3ce6af6b64c8b476de51ccc32da0cb3142d42e65754e1d8118addf65b8bcba15
 F src/expr.c 82797e5d82422d34ede9a95ba459f40c317b2daadb21109a21abfd42f84e3ed8
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
@@ -1928,7 +1928,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 54604869861cc5866d5de87785599ca56f75067f8cb7fe22e32912b3a037e37b
-R c102c10e7d90535120f47ae5b9d857b8
+P a0df216f7c3f8963efba0b1ffee65d6a63309d846ffdcf2d2932cb4f1d4967b7
+R 7f80422897fa74c39c1c69f1ebb4bc77
 U dan
-Z 5f5b68ce84257c8f070b0080ca6a87b5
+Z 911e4aa022339aecd631fddd7d57b6e4

diff --git a/manifest.uuid b/manifest.uuid
index 2cc8710f1954a10519c9e3d031194624623dd3e7..2fe5516a580a8c18c908873013ff78d8de7760f9 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-a0df216f7c3f8963efba0b1ffee65d6a63309d846ffdcf2d2932cb4f1d4967b7
\ No newline at end of file
+c4c705abc60624bf9ba4c1c05286b902b965f7ba9fd776c4ef8bc1fb78a4ccde
\ No newline at end of file

diff --git a/src/dbstat.c b/src/dbstat.c
index 33f9ea8f75f3f588a4ce35e3f5362e3192ee3614..bb88a76f4081a61ced4112f5c97e152b4c60f2d1 100644 (file)
--- a/src/dbstat.c
+++ b/src/dbstat.c
@@ -25,6 +25,15 @@
 #if (defined(SQLITE_ENABLE_DBSTAT_VTAB) || defined(SQLITE_TEST)) \
     && !defined(SQLITE_OMIT_VIRTUALTABLE)
 
+/*
+** The pager and btree modules arrange objects in memory so that there are
+** always approximately 200 bytes of addressable memory following each page
+** buffer. This way small buffer overreads caused by corrupt database pages
+** do not cause undefined behaviour. This module pads each page buffer
+** by the following number of bytes for the same purpose.
+*/
+#define DBSTAT_PAGE_PADDING_BYTES 256
+
 /*
 ** Page paths:
 ** 
@@ -459,7 +468,7 @@ static int statDecodePage(Btree *pBt, StatPage *p){
         if( nPayload>(u32)nLocal ){
           int j;
           int nOvfl = ((nPayload - nLocal) + nUsable-4 - 1) / (nUsable - 4);
-          if( iOff+nLocal>nUsable || nPayload>0x7fffffff ){
+          if( iOff+nLocal+4>nUsable || nPayload>0x7fffffff ){
             goto statPageIsCorrupt;
           }
           pCell->nLastOvfl = (nPayload-nLocal) - (nOvfl-1) * (nUsable-4);
@@ -533,10 +542,11 @@ static int statGetPage(
   int rc;
 
   if( pPg->aPg==0 ){
-    pPg->aPg = (u8*)sqlite3_malloc(pgsz);
+    pPg->aPg = (u8*)sqlite3_malloc(pgsz + DBSTAT_PAGE_PADDING_BYTES);
     if( pPg->aPg==0 ){
       return SQLITE_NOMEM_BKPT;
     }
+    memset(&pPg->aPg[pgsz], 0, DBSTAT_PAGE_PADDING_BYTES);
   }
 
   rc = sqlite3PagerGet(sqlite3BtreePager(pBt), iPg, &pDbPage, 0);