diff --git a/src/add-ons/kernel/file_systems/bfs/kernel_interface.cpp b/src/add-ons/kernel/file_systems/bfs/kernel_interface.cpp
index 270a4fa7c1..664751ddab 100644
--- a/src/add-ons/kernel/file_systems/bfs/kernel_interface.cpp
+++ b/src/add-ons/kernel/file_systems/bfs/kernel_interface.cpp
@@ -303,7 +303,7 @@ bfs_release_vnode(void *_ns, void *_node, bool reenter)
 
 	// since a directory's size can be changed without having it opened,
 	// we need to take care about their preallocated blocks here
-	if (inode->NeedsTrimming()) {
+	if (!volume->IsReadOnly() && inode->NeedsTrimming()) {
 		Transaction transaction(volume, inode->BlockNumber());
 
 		if (inode->TrimPreallocation(transaction) == B_OK)
@@ -932,11 +932,18 @@ bfs_rename(void *_ns, void *_oldDir, const char *oldName, void *_newDir, const c
 	if (oldDirectory == newDirectory && !strcmp(oldName, newName))
 		return B_OK;
 
+	// are we allowed to do what we've been told?
+	status_t status = oldDirectory->CheckPermissions(W_OK);
+	if (status == B_OK)
+		status = newDirectory->CheckPermissions(W_OK);
+	if (status < B_OK)
+		return status;
+
 	RecursiveLocker locker(volume->Lock());
 
 	// get the directory's tree, and a pointer to the inode which should be changed
 	BPlusTree *tree;
-	status_t status = oldDirectory->GetTree(&tree);
+	status = oldDirectory->GetTree(&tree);
 	if (status < B_OK)
 		RETURN_ERROR(status);