Add test that symlinking over a directory returns EEXIST.

Also remove comments in InodeOperations that required that implementation of
some Create* operations ensure that the name does not already exist, since
these checks are all centralized in the Dirent.

PiperOrigin-RevId: 241637335
Change-Id: Id098dc6063ff7c38347af29d1369075ad1e89a58

2 files changed, 1 insertions, 9 deletions

diff --git a/pkg/sentry/fs/inode_operations.go b/pkg/sentry/fs/inode_operations.go
index 548f1eb8b..e8b9ab96b 100644
--- a/pkg/sentry/fs/inode_operations.go
+++ b/pkg/sentry/fs/inode_operations.go
@@ -104,15 +104,12 @@ type InodeOperations interface {
 	CreateLink(ctx context.Context, dir *Inode, oldname string, newname string) error
 
 	// CreateHardLink creates a hard link under dir between the target
-	// Inode and name. Implementations must ensure that name does not
-	// already exist.
+	// Inode and name.
 	//
 	// The caller must ensure this operation is permitted.
 	CreateHardLink(ctx context.Context, dir *Inode, target *Inode, name string) error
 
 	// CreateFifo creates a new named pipe under dir at name.
-	// Implementations must ensure that an Inode at name does not
-	// already exist.
 	//
 	// The caller must ensure that this operation is permitted.
 	CreateFifo(ctx context.Context, dir *Inode, name string, perm FilePermissions) error
@@ -144,7 +141,6 @@ type InodeOperations interface {
 	Rename(ctx context.Context, oldParent *Inode, oldName string, newParent *Inode, newName string, replacement bool) error
 
 	// Bind binds a new socket under dir at the given name.
-	// Implementations must ensure that name does not already exist.
 	//
 	// The caller must ensure that this operation is permitted.
 	Bind(ctx context.Context, dir *Inode, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error)
diff --git a/pkg/sentry/fs/ramfs/dir.go b/pkg/sentry/fs/ramfs/dir.go
index b60dab243..05d716afb 100644
--- a/pkg/sentry/fs/ramfs/dir.go
+++ b/pkg/sentry/fs/ramfs/dir.go
@@ -268,10 +268,6 @@ func (d *Dir) createInodeOperationsCommon(ctx context.Context, name string, make
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	if _, ok := d.children[name]; ok {
-		return nil, syscall.EEXIST
-	}
-
 	inode, err := makeInodeOperations()
 	if err != nil {
 		return nil, err