Fix a read of invalid memory that could occur in btree.c. (CVS 2180)

FossilOrigin-Name: 929745c1833e7f4323884a1bc0c632f5b319da35

manifest

@@ -1,5 +1,5 @@
-C Remove\sincorrect\sassert()\sand\sadd\sextra\soption\sto\saccount\sfor\snon-standard\s'sort'\sprogram\sin\ssome\slinux\sversions.\s(CVS\s2179)
-D 2005-01-07T01:56:17
+C Fix\sa\sread\sof\sinvalid\smemory\sthat\scould\soccur\sin\sbtree.c.\s(CVS\s2180)
+D 2005-01-07T08:56:44
 F Makefile.in ecf441ac5ca1ccfc8748a8a9537706e69893dfa4
 F Makefile.linux-gcc a9e5a0d309fa7c38e7c14d3ecf7690879d3a5457
 F README a01693e454a00cc117967e3f9fdab2d4d52e9bc1
@@ -29,7 +29,7 @@ F sqlite3.def dbaeb20c153e1d366e8f421b55a573f5dfc00863
 F sqlite3.pc.in 985b9bf34192a549d7d370e0f0b6b34a4f61369a
 F src/attach.c e49d09dad9f5f9fb10b4b0c1be5a70ae4c45e689
 F src/auth.c 3b81f2a42f48a62c2c9c9b0eda31a157c681edea
-F src/btree.c fa113d624d38bcb36700a0244b47f39d57d34efb
+F src/btree.c 8cab7c66c822ae9c37c59a923ffec81927583ee2
 F src/btree.h 861e40b759a195ba63819740e484390012cf81ab
 F src/build.c af1296e8a21a406b4f4c4f1e1365e075071219f3
 F src/cursor.c f883813759742068890b1f699335872bfa8fdf41
@@ -263,7 +263,7 @@ F www/tclsqlite.tcl e73f8f8e5f20e8277619433f7970060ab01088fc
 F www/vdbe.tcl 095f106d93875c94b47367384ebc870517431618
 F www/version3.tcl 092a01f5ef430d2c4acc0ae558d74c4bb89638a0
 F www/whentouse.tcl c3b50d3ac31c54be2a1af9b488a89d22f1e6e746
-P 9d674d1dc09f72c64ef7f37cd9838c7a9c50b746
-R d21fa91d39b388686915b90d94c4baf8
+P bf14387697459d8d348a35ca50e2ee9407dcf1e1
+R 69691ec0fc90d47f2795ea61e7840061
 U danielk1977
-Z d4d186f3d78d137c0d019d40b89696b1
+Z 5456339343e3dea6f3d7b76699be8b22

manifest.uuid

@@ -1 +1 @@
-bf14387697459d8d348a35ca50e2ee9407dcf1e1
+929745c1833e7f4323884a1bc0c632f5b319da35

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.225 2004/11/23 09:06:56 danielk1977 Exp $
+** $Id: btree.c,v 1.226 2005/01/07 08:56:44 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -3429,13 +3429,19 @@ static void dropCell(MemPage *pPage, int idx, int sz){
 ** in pTemp or the original pCell) and also record its index. 
 ** Allocating a new entry in pPage->aCell[] implies that 
 ** pPage->nOverflow is incremented.
+**
+** If nSkip is non-zero, then do not copy the first nSkip bytes of the
+** cell. The caller will overwrite them after this function returns. If
+** nSkip is non-zero, then pCell may not point to a valid memory location 
+** (but pCell+nSkip is always valid).
 */
 static int insertCell(
   MemPage *pPage,   /* Page into which we are copying */
   int i,            /* New cell becomes the i-th cell of the page */
   u8 *pCell,        /* Content of the new cell */
   int sz,           /* Bytes of content in pCell */
-  u8 *pTemp         /* Temp storage space for pCell, if needed */
+  u8 *pTemp,        /* Temp storage space for pCell, if needed */
+  u8 nSkip          /* Do not write the first nSkip bytes of the cell */
 ){
   int idx;          /* Where to write new cell content in data[] */
   int j;            /* Loop counter */
@@ -3452,7 +3458,7 @@ static int insertCell(
   assert( sqlite3pager_iswriteable(pPage->aData) );
   if( pPage->nOverflow || sz+2>pPage->nFree ){
     if( pTemp ){
-      memcpy(pTemp, pCell, sz);
+      memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
       pCell = pTemp;
     }
     j = pPage->nOverflow++;
@@ -3477,7 +3483,7 @@ static int insertCell(
     assert( end <= get2byte(&data[hdr+5]) );
     pPage->nCell++;
     pPage->nFree -= 2;
-    memcpy(&data[idx], pCell, sz);
+    memcpy(&data[idx+nSkip], pCell+nSkip, sz-nSkip);
     for(j=end-2, ptr=&data[j]; j>ins; j-=2, ptr-=2){
       ptr[0] = ptr[-2];
       ptr[1] = ptr[-1];
@@ -3963,7 +3969,7 @@ static int balance_nonroot(MemPage *pPage){
         iSpace += sz;
         assert( iSpace<=pBt->psAligned*5 );
       }
-      rc = insertCell(pParent, nxDiv, pCell, sz, pTemp);
+      rc = insertCell(pParent, nxDiv, pCell, sz, pTemp, 4);
       if( rc!=SQLITE_OK ) goto balance_cleanup;
       put4byte(findOverflowCell(pParent,nxDiv), pNew->pgno);
       j++;
@@ -4275,7 +4281,7 @@ int sqlite3BtreeInsert(
   }else{
     assert( pPage->leaf );
   }
-  rc = insertCell(pPage, pCur->idx, newCell, szNew, 0);
+  rc = insertCell(pPage, pCur->idx, newCell, szNew, 0, 0);
   if( rc!=SQLITE_OK ) goto end_insert;
   rc = balance(pPage);
   /* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
@@ -4362,7 +4368,7 @@ int sqlite3BtreeDelete(BtCursor *pCur){
     assert( MX_CELL_SIZE(pBt)>=szNext+4 );
     tempCell = sqliteMallocRaw( MX_CELL_SIZE(pBt) );
     if( tempCell==0 ) return SQLITE_NOMEM;
-    rc = insertCell(pPage, pCur->idx, pNext-4, szNext+4, tempCell);
+    rc = insertCell(pPage, pCur->idx, pNext-4, szNext+4, tempCell, 0);
     if( rc!=SQLITE_OK ) return rc;
     put4byte(findOverflowCell(pPage, pCur->idx), pgnoChild);
     rc = balance(pPage);