Implement RENAME_NOREPLACE for all VFS2 filesystem implementations.

PiperOrigin-RevId: 377966969

4 files changed, 49 insertions, 21 deletions

diff --git a/pkg/sentry/fsimpl/gofer/filesystem.go b/pkg/sentry/fsimpl/gofer/filesystem.go
index 91ec4a142..eb09d54c3 100644
--- a/pkg/sentry/fsimpl/gofer/filesystem.go
+++ b/pkg/sentry/fsimpl/gofer/filesystem.go
@@ -1194,11 +1194,7 @@ func (fs *filesystem) ReadlinkAt(ctx context.Context, rp *vfs.ResolvingPath) (st
 
 // RenameAt implements vfs.FilesystemImpl.RenameAt.
 func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldParentVD vfs.VirtualDentry, oldName string, opts vfs.RenameOptions) error {
-	if opts.Flags != 0 {
-		// Requires 9P support.
-		return syserror.EINVAL
-	}
-
+	// Resolve newParent first to verify that it's on this Mount.
 	var ds *[]*dentry
 	fs.renameMu.Lock()
 	defer fs.renameMuUnlockAndCheckCaching(ctx, &ds)
@@ -1206,8 +1202,21 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	if err != nil {
 		return err
 	}
+
+	if opts.Flags&^linux.RENAME_NOREPLACE != 0 {
+		return syserror.EINVAL
+	}
+	if fs.opts.interop == InteropModeShared && opts.Flags&linux.RENAME_NOREPLACE != 0 {
+		// Requires 9P support to synchronize with other remote filesystem
+		// users.
+		return syserror.EINVAL
+	}
+
 	newName := rp.Component()
 	if newName == "." || newName == ".." {
+		if opts.Flags&linux.RENAME_NOREPLACE != 0 {
+			return syserror.EEXIST
+		}
 		return syserror.EBUSY
 	}
 	mnt := rp.Mount()
@@ -1280,6 +1289,9 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	}
 	var replacedVFSD *vfs.Dentry
 	if replaced != nil {
+		if opts.Flags&linux.RENAME_NOREPLACE != 0 {
+			return syserror.EEXIST
+		}
 		replacedVFSD = &replaced.vfsd
 		if replaced.isDir() {
 			if !renamed.isDir() {
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index f50b0fb08..8fac53c60 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -635,12 +635,6 @@ func (fs *Filesystem) ReadlinkAt(ctx context.Context, rp *vfs.ResolvingPath) (st
 
 // RenameAt implements vfs.FilesystemImpl.RenameAt.
 func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldParentVD vfs.VirtualDentry, oldName string, opts vfs.RenameOptions) error {
-	// Only RENAME_NOREPLACE is supported.
-	if opts.Flags&^linux.RENAME_NOREPLACE != 0 {
-		return syserror.EINVAL
-	}
-	noReplace := opts.Flags&linux.RENAME_NOREPLACE != 0
-
 	fs.mu.Lock()
 	defer fs.processDeferredDecRefs(ctx)
 	defer fs.mu.Unlock()
@@ -651,6 +645,13 @@ func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	if err != nil {
 		return err
 	}
+
+	// Only RENAME_NOREPLACE is supported.
+	if opts.Flags&^linux.RENAME_NOREPLACE != 0 {
+		return syserror.EINVAL
+	}
+	noReplace := opts.Flags&linux.RENAME_NOREPLACE != 0
+
 	mnt := rp.Mount()
 	if mnt != oldParentVD.Mount() {
 		return syserror.EXDEV
diff --git a/pkg/sentry/fsimpl/overlay/filesystem.go b/pkg/sentry/fsimpl/overlay/filesystem.go
index 46c500427..6b6fa0bd5 100644
--- a/pkg/sentry/fsimpl/overlay/filesystem.go
+++ b/pkg/sentry/fsimpl/overlay/filesystem.go
@@ -1017,10 +1017,7 @@ func (fs *filesystem) ReadlinkAt(ctx context.Context, rp *vfs.ResolvingPath) (st
 
 // RenameAt implements vfs.FilesystemImpl.RenameAt.
 func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldParentVD vfs.VirtualDentry, oldName string, opts vfs.RenameOptions) error {
-	if opts.Flags != 0 {
-		return syserror.EINVAL
-	}
-
+	// Resolve newParent first to verify that it's on this Mount.
 	var ds *[]*dentry
 	fs.renameMu.Lock()
 	defer fs.renameMuUnlockAndCheckDrop(ctx, &ds)
@@ -1028,8 +1025,16 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	if err != nil {
 		return err
 	}
+
+	if opts.Flags&^linux.RENAME_NOREPLACE != 0 {
+		return syserror.EINVAL
+	}
+
 	newName := rp.Component()
 	if newName == "." || newName == ".." {
+		if opts.Flags&linux.RENAME_NOREPLACE != 0 {
+			return syserror.EEXIST
+		}
 		return syserror.EBUSY
 	}
 	mnt := rp.Mount()
@@ -1093,6 +1098,9 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 		return err
 	}
 	if replaced != nil {
+		if opts.Flags&linux.RENAME_NOREPLACE != 0 {
+			return syserror.EEXIST
+		}
 		replacedVFSD = &replaced.vfsd
 		if replaced.isDir() {
 			if !renamed.isDir() {
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 766289e60..ee7ff2961 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -496,20 +496,24 @@ func (fs *filesystem) ReadlinkAt(ctx context.Context, rp *vfs.ResolvingPath) (st
 
 // RenameAt implements vfs.FilesystemImpl.RenameAt.
 func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldParentVD vfs.VirtualDentry, oldName string, opts vfs.RenameOptions) error {
-	if opts.Flags != 0 {
-		// TODO(b/145974740): Support renameat2 flags.
-		return syserror.EINVAL
-	}
-
-	// Resolve newParent first to verify that it's on this Mount.
+	// Resolve newParentDir first to verify that it's on this Mount.
 	fs.mu.Lock()
 	defer fs.mu.Unlock()
 	newParentDir, err := walkParentDirLocked(ctx, rp, rp.Start().Impl().(*dentry))
 	if err != nil {
 		return err
 	}
+
+	if opts.Flags&^linux.RENAME_NOREPLACE != 0 {
+		// TODO(b/145974740): Support other renameat2 flags.
+		return syserror.EINVAL
+	}
+
 	newName := rp.Component()
 	if newName == "." || newName == ".." {
+		if opts.Flags&linux.RENAME_NOREPLACE != 0 {
+			return syserror.EEXIST
+		}
 		return syserror.EBUSY
 	}
 	mnt := rp.Mount()
@@ -556,6 +560,9 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	}
 	replaced, ok := newParentDir.childMap[newName]
 	if ok {
+		if opts.Flags&linux.RENAME_NOREPLACE != 0 {
+			return syserror.EEXIST
+		}
 		replacedDir, ok := replaced.inode.impl.(*directory)
 		if ok {
 			if !renamed.inode.isDir() {