1 files changed, 26 insertions, 16 deletions
diff --git a/src/main.c b/src/main.c
index e2d272157..3ed21e423 100644
--- a/src/main.c
+++ b/src/main.c
@@ -759,17 +759,22 @@ int sqlite3_config(int op, ...){
 ** If lookaside is already active, return SQLITE_BUSY.
 **
 ** The sz parameter is the number of bytes in each lookaside slot.
-** The cnt parameter is the number of slots.  If pStart is NULL the
-** space for the lookaside memory is obtained from sqlite3_malloc().
-** If pStart is not NULL then it is sz*cnt bytes of memory to use for
-** the lookaside memory.
+** The cnt parameter is the number of slots.  If pBuf is NULL the
+** space for the lookaside memory is obtained from sqlite3_malloc()
+** or similar.  If pBuf is not NULL then it is sz*cnt bytes of memory
+** to use for the lookaside memory.
 */
-static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
+static int setupLookaside(
+  sqlite3 *db,    /* Database connection being configured */
+  void *pBuf,     /* Memory to use for lookaside.  May be NULL */
+  int sz,         /* Desired size of each lookaside memory slot */
+  int cnt         /* Number of slots to allocate */
+){
 #ifndef SQLITE_OMIT_LOOKASIDE
-  void *pStart;
-  sqlite3_int64 szAlloc = sz*(sqlite3_int64)cnt;
-  int nBig;   /* Number of full-size slots */
-  int nSm;    /* Number smaller LOOKASIDE_SMALL-byte slots */
+  void *pStart;          /* Start of the lookaside buffer */
+  sqlite3_int64 szAlloc; /* Total space set aside for lookaside memory */
+  int nBig;              /* Number of full-size slots */
+  int nSm;               /* Number smaller LOOKASIDE_SMALL-byte slots */
  
   if( sqlite3LookasideUsed(db,0)>0 ){
     return SQLITE_BUSY;
@@ -782,17 +787,22 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
     sqlite3_free(db->lookaside.pStart);
   }
   /* The size of a lookaside slot after ROUNDDOWN8 needs to be larger
-  ** than a pointer to be useful.
+  ** than a pointer and small enough to fit in a u16.
   */
-  sz = ROUNDDOWN8(sz);  /* IMP: R-33038-09382 */
+  sz = ROUNDDOWN8(sz);
   if( sz<=(int)sizeof(LookasideSlot*) ) sz = 0;
-  if( cnt<0 ) cnt = 0;
-  if( sz==0 || cnt==0 ){
+  if( sz>65528 ) sz = 65528;
+  /* Count must be at least 1 to be useful, but not so large as to use
+  ** more than 0x7fff0000 total bytes for lookaside. */
+  if( cnt<1 ) cnt = 0;
+  if( sz>0 && cnt>(0x7fff0000/sz) ) cnt = 0x7fff0000/sz;
+  szAlloc = (i64)sz*(i64)cnt;
+  if( szAlloc==0 ){
     sz = 0;
     pStart = 0;
   }else if( pBuf==0 ){
     sqlite3BeginBenignMalloc();
-    pStart = sqlite3Malloc( szAlloc );  /* IMP: R-61949-35727 */
+    pStart = sqlite3Malloc( szAlloc );
     sqlite3EndBenignMalloc();
     if( pStart ) szAlloc = sqlite3MallocSize(pStart);
   }else{
@@ -801,10 +811,10 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
 #ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
   if( sz>=LOOKASIDE_SMALL*3 ){
     nBig = szAlloc/(3*LOOKASIDE_SMALL+sz);
-    nSm = (szAlloc - sz*nBig)/LOOKASIDE_SMALL;
+    nSm = (szAlloc - (i64)sz*(i64)nBig)/LOOKASIDE_SMALL;
   }else if( sz>=LOOKASIDE_SMALL*2 ){
     nBig = szAlloc/(LOOKASIDE_SMALL+sz);
-    nSm = (szAlloc - sz*nBig)/LOOKASIDE_SMALL;
+    nSm = (szAlloc - (i64)sz*(i64)nBig)/LOOKASIDE_SMALL;
   }else
 #endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
   if( sz>0 ){