Add MDB_CLEANMEM option.

Initialize unused portions of DB pages, for security or to silence
checkers like Purify and Valgrind. Like BDB configure --enable-umrw.

libraries/liblmdb/lmdb.h

@@ -70,6 +70,12 @@
  *	  access to locks and lock file. Exceptions: On read-only filesystems
  *	  or with the #MDB_NOLOCK flag described under #mdb_env_open().
  *
+ *	- By default, unused portions of the datafile may receive garbage data
+ *	  from memory freed by other code. (This does not happen when using
+ *	  the #MDB_WRITEMAP flag.) Applications handling sensitive data
+ *	  which must not be written, and which don't use #MDB_WRITEMAP,
+ *	  need to prevent this with the #MDB_CLEANMEM flag.
+ *
  *	- A thread can only use one transaction at a time, plus any child
  *	  transactions.  Each transaction belongs to one thread.  See below.
  *	  The #MDB_NOTLS flag changes this for read-only transactions.
@@ -277,6 +283,8 @@ typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *rel
 #define MDB_NOLOCK		0x400000
 	/** don't do readahead (no effect on Windows) */
 #define MDB_NORDAHEAD	0x800000
+	/** don't write uninitialized malloc'd memory to datafile */
+#define MDB_CLEANMEM	0x1000000
 /** @} */
 
 /**	@defgroup	mdb_dbi_open	Database Flags
@@ -546,6 +554,22 @@ int  mdb_env_create(MDB_env **env);
 	 *		supports it. Turning it off may help random read performance
 	 *		when the DB is larger than RAM and system RAM is full.
 	 *		The option is not implemented on Windows.
+	 *	<li>#MDB_CLEANMEM
+	 *		Don't write uninitialized memory to unused spaces in the datafile.
+	 *		By default, memory for pages written to the datafile is obtained
+	 *		using malloc, and only the portions that LMDB uses are modified.
+	 *		Unused portions of a page may contain leftover data from other
+	 *		code that used the heap and subsequently freed that memory.
+	 *		That can be a problem for applications which handle sensitive data
+	 *		like passwords, and it makes memory checkers like Valgrind noisy.
+	 *		With this flag, unused portions of pages will be initialized to
+	 *		zero. This flag is not needed with #MDB_WRITEMAP, which writes
+	 *		directly to the mmap instead of using malloc for pages. The
+	 *		initialization is also skipped if #MDB_RESERVE is used; the
+	 *		caller is expected to overwrite all of the memory that was
+	 *		reserved in that case.
+	 *		This flag may be changed at any time using #mdb_env_set_flags().
+	 *		It comes at some performance cost.
 	 * </ul>
 	 * @param[in] mode The UNIX permissions to set on created files. This parameter
 	 * is ignored on Windows.
@@ -1131,6 +1155,8 @@ int  mdb_get(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data);
 	 *		reserved space, which the caller can fill in later - before
 	 *		the next update operation or the transaction ends. This saves
 	 *		an extra memcpy if the data is being generated later.
+	 *		MDB does nothing else with this memory, even if #MDB_CLEANMEM is
+	 *		set - the caller is expected to modify all of the space requested.
 	 *	<li>#MDB_APPEND - append the given key/data pair to the end of the
 	 *		database. No key comparisons are performed. This option allows
 	 *		fast bulk loading when keys are already known to be in the

libraries/liblmdb/mdb.c

@@ -1322,7 +1322,12 @@ mdb_page_malloc(MDB_txn *txn, unsigned num)
 {
 	MDB_env *env = txn->mt_env;
 	MDB_page *ret = env->me_dpages;
-	size_t sz = env->me_psize;
+	size_t psize = env->me_psize, sz = psize, off;
+	/* For #MDB_CLEANMEM, psize counts how much to init.
+	 * For a single page alloc, we init everything after the page header.
+	 * For multi-page, we init the final page; if the caller needed that
+	 * many pages they will be filling in at least up to the last page.
+	 */
 	if (num == 1) {
 		if (ret) {
 			VGMEMP_ALLOC(env, ret, sz);
@@ -1330,10 +1335,16 @@ mdb_page_malloc(MDB_txn *txn, unsigned num)
 			env->me_dpages = ret->mp_next;
 			return ret;
 		}
+		psize -= off = PAGEHDRSZ;
 	} else {
 		sz *= num;
+		off = sz - psize;
 	}
 	if ((ret = malloc(sz)) != NULL) {
+		if (env->me_flags & MDB_CLEANMEM) {
+			memset((char *)ret + off, 0, psize);
+			ret->mp_pad = 0;
+		}
 		VGMEMP_ALLOC(env, ret, sz);
 	}
 	return ret;
@@ -2486,7 +2497,7 @@ mdb_freelist_save(MDB_txn *txn)
 	int rc, maxfree_1pg = env->me_maxfree_1pg, more = 1;
 	txnid_t	pglast = 0, head_id = 0;
 	pgno_t	freecnt = 0, *free_pgs, *mop;
-	ssize_t	head_room = 0, total_room = 0, mop_len;
+	ssize_t	head_room = 0, total_room = 0, mop_len, clean_limit;
 
 	mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
 
@@ -2497,9 +2508,15 @@ mdb_freelist_save(MDB_txn *txn)
 			return rc;
 	}
 
+	/* MDB_RESERVE cancels CLEANMEM in ovpage malloc (when no WRITEMAP) */
+	clean_limit = (env->me_flags & (MDB_CLEANMEM|MDB_WRITEMAP)) == MDB_CLEANMEM
+		? maxfree_1pg : SSIZE_MAX;
+
 	for (;;) {
 		/* Come back here after each Put() in case freelist changed */
 		MDB_val key, data;
+		pgno_t *pgs;
+		ssize_t j;
 
 		/* If using records from freeDB which we have not yet
 		 * deleted, delete them and any we reserved for me_pghead.
@@ -2583,7 +2600,12 @@ mdb_freelist_save(MDB_txn *txn)
 		rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
 		if (rc)
 			return rc;
-		*(MDB_ID *)data.mv_data = 0; /* IDL is initially empty */
+		/* IDL is initially empty, zero out at least the length */
+		pgs = (pgno_t *)data.mv_data;
+		j = head_room > clean_limit ? head_room : 0;
+		do {
+			pgs[j] = 0;
+		} while (--j >= 0);
 		total_room += head_room;
 	}
 
@@ -3943,8 +3965,9 @@ fail:
 	 *	at runtime. Changing other flags requires closing the
 	 *	environment and re-opening it with the new flags.
 	 */
-#define	CHANGEABLE	(MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC)
+#define	CHANGEABLE	(MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_CLEANMEM)
-#define	CHANGELESS	(MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY|MDB_WRITEMAP|MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
+#define	CHANGELESS	(MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY|MDB_WRITEMAP| \
+	MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
 
 int
 mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode)
@@ -5847,12 +5870,14 @@ more:
 				if (NODESIZE + sizeof(indx_t) + NODEKSZ(leaf) + xdata.mv_size
 					>= env->me_nodemax) {
 					/* yes, convert it */
-					dummy.md_flags = 0;
 					if (mc->mc_db->md_flags & MDB_DUPFIXED) {
 						dummy.md_pad = fp->mp_pad;
 						dummy.md_flags = MDB_DUPFIXED;
 						if (mc->mc_db->md_flags & MDB_INTEGERDUP)
 							dummy.md_flags |= MDB_INTEGERKEY;
+					} else {
+						dummy.md_pad = 0;
+						dummy.md_flags = 0;
 					}
 					dummy.md_depth = 1;
 					dummy.md_branch_pages = 0;

libraries/liblmdb/mtest.c

@@ -28,7 +28,7 @@ int main(int argc,char * argv[])
 	MDB_cursor *cursor, *cur2;
 	int count;
 	int *values;
-	char sval[32];
+	char sval[32] = "";
 
 	srandom(time(NULL));
 

libraries/liblmdb/mtest2.c

@@ -31,7 +31,7 @@ int main(int argc,char * argv[])
 	MDB_cursor *cursor;
 	int count;
 	int *values;
-	char sval[32];
+	char sval[32] = "";
 
 	srandom(time(NULL));