Index: src/os_unix.c
==================================================================
--- src/os_unix.c
+++ src/os_unix.c
@@ -3856,10 +3856,17 @@
       i64 newLimit = *(i64*)pArg;
       int rc = SQLITE_OK;
       if( newLimit>sqlite3GlobalConfig.mxMmap ){
         newLimit = sqlite3GlobalConfig.mxMmap;
       }
+
+      /* The value of newLimit may be eventually cast to (size_t) and passed
+      ** to mmap(). Restrict its value to 2GB if (size_t) is a 32-bit type. */
+      if( sizeof(size_t)<8 ){
+        newLimit = (newLimit & 0x7FFFFFFF);
+      }
+
       *(i64*)pArg = pFile->mmapSizeMax;
       if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){
         pFile->mmapSizeMax = newLimit;
         if( pFile->mmapSize>0 ){
           unixUnmapfile(pFile);