Plumb getting/setting xattrs through InodeOperations and 9p gofer interfaces.

There was a very bare get/setxattr in the InodeOperations interface. Add
context.Context to both, size to getxattr, and flags to setxattr.
Note that extended attributes are passed around as strings in this
implementation, so size is automatically encoded into the value. Size is
added in getxattr so that implementations can return ERANGE if a value is larger
than can fit in the user-allocated buffer. This prevents us from unnecessarily
passing around an arbitrarily large xattr when the user buffer is actually too
small.

Don't use the existing xattrwalk and xattrcreate messages and define our
own, mainly for the sake of simplicity.

Extended attributes will be implemented in future commits.

PiperOrigin-RevId: 290121300

1 files changed, 15 insertions, 15 deletions

diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index 13d11e001..b90da20d0 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -25,13 +25,13 @@ import (
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
-func overlayHasWhiteout(parent *Inode, name string) bool {
-	s, err := parent.Getxattr(XattrOverlayWhiteout(name))
+func overlayHasWhiteout(ctx context.Context, parent *Inode, name string) bool {
+	s, err := parent.GetXattr(ctx, XattrOverlayWhiteout(name), 1)
 	return err == nil && s == "y"
 }
 
-func overlayCreateWhiteout(parent *Inode, name string) error {
-	return parent.InodeOperations.Setxattr(parent, XattrOverlayWhiteout(name), "y")
+func overlayCreateWhiteout(ctx context.Context, parent *Inode, name string) error {
+	return parent.InodeOperations.SetXattr(ctx, parent, XattrOverlayWhiteout(name), "y", 0 /* flags */)
 }
 
 func overlayWriteOut(ctx context.Context, o *overlayEntry) error {
@@ -89,7 +89,7 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
 		}
 
 		// Are we done?
-		if overlayHasWhiteout(parent.upper, name) {
+		if overlayHasWhiteout(ctx, parent.upper, name) {
 			if upperInode == nil {
 				parent.copyMu.RUnlock()
 				if negativeUpperChild {
@@ -345,7 +345,7 @@ func overlayRemove(ctx context.Context, o *overlayEntry, parent *Dirent, child *
 		}
 	}
 	if child.Inode.overlay.lowerExists {
-		if err := overlayCreateWhiteout(o.upper, child.name); err != nil {
+		if err := overlayCreateWhiteout(ctx, o.upper, child.name); err != nil {
 			return err
 		}
 	}
@@ -426,7 +426,7 @@ func overlayRename(ctx context.Context, o *overlayEntry, oldParent *Dirent, rena
 		return err
 	}
 	if renamed.Inode.overlay.lowerExists {
-		if err := overlayCreateWhiteout(oldParent.Inode.overlay.upper, oldName); err != nil {
+		if err := overlayCreateWhiteout(ctx, oldParent.Inode.overlay.upper, oldName); err != nil {
 			return err
 		}
 	}
@@ -528,7 +528,7 @@ func overlayUnstableAttr(ctx context.Context, o *overlayEntry) (UnstableAttr, er
 	return attr, err
 }
 
-func overlayGetxattr(o *overlayEntry, name string) (string, error) {
+func overlayGetXattr(ctx context.Context, o *overlayEntry, name string, size uint64) (string, error) {
 	// Hot path. This is how the overlay checks for whiteout files.
 	// Avoid defers.
 	var (
@@ -544,31 +544,31 @@ func overlayGetxattr(o *overlayEntry, name string) (string, error) {
 
 	o.copyMu.RLock()
 	if o.upper != nil {
-		s, err = o.upper.Getxattr(name)
+		s, err = o.upper.GetXattr(ctx, name, size)
 	} else {
-		s, err = o.lower.Getxattr(name)
+		s, err = o.lower.GetXattr(ctx, name, size)
 	}
 	o.copyMu.RUnlock()
 	return s, err
 }
 
 // TODO(b/146028302): Support setxattr for overlayfs.
-func overlaySetxattr(o *overlayEntry, name, value string) error {
+func overlaySetxattr(ctx context.Context, o *overlayEntry, name, value string, flags uint32) error {
 	return syserror.EOPNOTSUPP
 }
 
-func overlayListxattr(o *overlayEntry) (map[string]struct{}, error) {
+func overlayListXattr(ctx context.Context, o *overlayEntry) (map[string]struct{}, error) {
 	o.copyMu.RLock()
 	defer o.copyMu.RUnlock()
 	var names map[string]struct{}
 	var err error
 	if o.upper != nil {
-		names, err = o.upper.Listxattr()
+		names, err = o.upper.ListXattr(ctx)
 	} else {
-		names, err = o.lower.Listxattr()
+		names, err = o.lower.ListXattr(ctx)
 	}
 	for name := range names {
-		// Same as overlayGetxattr, we shouldn't forward along
+		// Same as overlayGetXattr, we shouldn't forward along
 		// overlay attributes.
 		if strings.HasPrefix(XattrOverlayPrefix, name) {
 			delete(names, name)