ntdb: make sure file is always a multiple of PAGESIZE (now NTDB_PGSIZE)

ntdb uses tdb's transaction code, and it has an undocumented but implicit
assumption: that the transaction recovery area is always aligned to the
transaction pagesize.  This means that no block will overlap the recovery
area.

This is maintained by rounding the size of the database up, so do the same
for ntdb.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 8 insertions, 3 deletions

diff --git a/lib/ntdb/free.c b/lib/ntdb/free.c
index 0fe6c73775..f51aa5bc33 100644
--- a/lib/ntdb/free.c
+++ b/lib/ntdb/free.c
@@ -899,9 +899,14 @@ ntdb_off_t ntdb_expand_adjust(ntdb_off_t map_size, ntdb_off_t size)
 		new_size = map_size * 1.25;
 	}
 
-	/* Round the database up to a multiple of the page size */
 	if (new_size < top_size)
 		new_size = top_size;
+
+	/* We always make the file a multiple of transaction page
+	 * size.  This guarantees that the transaction recovery area
+	 * is always aligned, otherwise the transaction code can overwrite
+	 * itself. */
+	new_size = (new_size + NTDB_PGSIZE-1) & ~(NTDB_PGSIZE-1);
 	return new_size - map_size;
 }
 
@@ -933,10 +938,10 @@ static enum NTDB_ERROR ntdb_expand(struct ntdb_context *ntdb, ntdb_len_t size)
 		return NTDB_SUCCESS;
 	}
 
+	/* We need room for the record header too. */
+	size = adjust_size(0, sizeof(struct ntdb_used_record) + size);
 	/* Overallocate. */
 	wanted = ntdb_expand_adjust(old_size, size);
-	/* We need room for the record header too. */
-	wanted = adjust_size(0, sizeof(struct ntdb_used_record) + wanted);
 
 	ecode = ntdb->io->expand_file(ntdb, wanted);
 	if (ecode != NTDB_SUCCESS) {