Port extended attributes to VFS2.

As in VFS1, we only support the user.* namespace. Plumbing is added to tmpfs
and goferfs.
Note that because of the slightly different order of checks between VFS2 and
Linux, one of the xattr tests needs to be relaxed slightly.

Fixes #2363.

PiperOrigin-RevId: 305985121

1 files changed, 21 insertions, 11 deletions

diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index 20c545fca..4fb9aea87 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -401,11 +401,11 @@ type FileDescriptionImpl interface {
 	Ioctl(ctx context.Context, uio usermem.IO, args arch.SyscallArguments) (uintptr, error)
 
 	// Listxattr returns all extended attribute names for the file.
-	Listxattr(ctx context.Context) ([]string, error)
+	Listxattr(ctx context.Context, size uint64) ([]string, error)
 
 	// Getxattr returns the value associated with the given extended attribute
 	// for the file.
-	Getxattr(ctx context.Context, name string) (string, error)
+	Getxattr(ctx context.Context, opts GetxattrOptions) (string, error)
 
 	// Setxattr changes the value associated with the given extended attribute
 	// for the file.
@@ -605,18 +605,23 @@ func (fd *FileDescription) Ioctl(ctx context.Context, uio usermem.IO, args arch.
 
 // Listxattr returns all extended attribute names for the file represented by
 // fd.
-func (fd *FileDescription) Listxattr(ctx context.Context) ([]string, error) {
+//
+// If the size of the list (including a NUL terminating byte after every entry)
+// would exceed size, ERANGE may be returned. Note that implementations
+// are free to ignore size entirely and return without error). In all cases,
+// if size is 0, the list should be returned without error, regardless of size.
+func (fd *FileDescription) Listxattr(ctx context.Context, size uint64) ([]string, error) {
 	if fd.opts.UseDentryMetadata {
 		vfsObj := fd.vd.mount.vfs
 		rp := vfsObj.getResolvingPath(auth.CredentialsFromContext(ctx), &PathOperation{
 			Root:  fd.vd,
 			Start: fd.vd,
 		})
-		names, err := fd.vd.mount.fs.impl.ListxattrAt(ctx, rp)
+		names, err := fd.vd.mount.fs.impl.ListxattrAt(ctx, rp, size)
 		vfsObj.putResolvingPath(rp)
 		return names, err
 	}
-	names, err := fd.impl.Listxattr(ctx)
+	names, err := fd.impl.Listxattr(ctx, size)
 	if err == syserror.ENOTSUP {
 		// Linux doesn't actually return ENOTSUP in this case; instead,
 		// fs/xattr.c:vfs_listxattr() falls back to allowing the security
@@ -629,34 +634,39 @@ func (fd *FileDescription) Listxattr(ctx context.Context) ([]string, error) {
 
 // Getxattr returns the value associated with the given extended attribute for
 // the file represented by fd.
-func (fd *FileDescription) Getxattr(ctx context.Context, name string) (string, error) {
+//
+// If the size of the return value exceeds opts.Size, ERANGE may be returned
+// (note that implementations are free to ignore opts.Size entirely and return
+// without error). In all cases, if opts.Size is 0, the value should be
+// returned without error, regardless of size.
+func (fd *FileDescription) Getxattr(ctx context.Context, opts *GetxattrOptions) (string, error) {
 	if fd.opts.UseDentryMetadata {
 		vfsObj := fd.vd.mount.vfs
 		rp := vfsObj.getResolvingPath(auth.CredentialsFromContext(ctx), &PathOperation{
 			Root:  fd.vd,
 			Start: fd.vd,
 		})
-		val, err := fd.vd.mount.fs.impl.GetxattrAt(ctx, rp, name)
+		val, err := fd.vd.mount.fs.impl.GetxattrAt(ctx, rp, *opts)
 		vfsObj.putResolvingPath(rp)
 		return val, err
 	}
-	return fd.impl.Getxattr(ctx, name)
+	return fd.impl.Getxattr(ctx, *opts)
 }
 
 // Setxattr changes the value associated with the given extended attribute for
 // the file represented by fd.
-func (fd *FileDescription) Setxattr(ctx context.Context, opts SetxattrOptions) error {
+func (fd *FileDescription) Setxattr(ctx context.Context, opts *SetxattrOptions) error {
 	if fd.opts.UseDentryMetadata {
 		vfsObj := fd.vd.mount.vfs
 		rp := vfsObj.getResolvingPath(auth.CredentialsFromContext(ctx), &PathOperation{
 			Root:  fd.vd,
 			Start: fd.vd,
 		})
-		err := fd.vd.mount.fs.impl.SetxattrAt(ctx, rp, opts)
+		err := fd.vd.mount.fs.impl.SetxattrAt(ctx, rp, *opts)
 		vfsObj.putResolvingPath(rp)
 		return err
 	}
-	return fd.impl.Setxattr(ctx, opts)
+	return fd.impl.Setxattr(ctx, *opts)
 }
 
 // Removexattr removes the given extended attribute from the file represented