fusefrontend: run acl Setxattr in user context

The result of setting an acl depends on who runs the
operation!

Fixes fuse-xfstests generic/375
(see https://github.com/rfjakob/fuse-xfstests/wiki/results_2021-05-19)

3 files changed, 15 insertions, 5 deletions

diff --git a/internal/fusefrontend/node_xattr.go b/internal/fusefrontend/node_xattr.go
index 925dcbf..ceb10f1 100644
--- a/internal/fusefrontend/node_xattr.go
+++ b/internal/fusefrontend/node_xattr.go
@@ -7,6 +7,8 @@ import (
 	"strings"
 	"syscall"
 
+	"github.com/hanwen/go-fuse/v2/fuse"
+
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
@@ -90,7 +92,12 @@ func (n *Node) Setxattr(ctx context.Context, attr string, data []byte, flags uin
 
 	// ACLs are passed through without encryption
 	if isAcl(attr) {
-		return n.setXAttr(attr, data, flags)
+		// result of setting an acl depends on the user doing it
+		var context *fuse.Context
+		if rn.args.PreserveOwner {
+			context = toFuseCtx(ctx)
+		}
+		return n.setXAttr(context, attr, data, flags)
 	}
 
 	cAttr, err := rn.encryptXattrName(attr)
@@ -98,7 +105,7 @@ func (n *Node) Setxattr(ctx context.Context, attr string, data []byte, flags uin
 		return syscall.EINVAL
 	}
 	cData := rn.encryptXattrValue(data)
-	return n.setXAttr(cAttr, cData, flags)
+	return n.setXAttr(nil, cAttr, cData, flags)
 }
 
 // RemoveXAttr - FUSE call.
diff --git a/internal/fusefrontend/node_xattr_darwin.go b/internal/fusefrontend/node_xattr_darwin.go
index 82c0dff..0f61a5d 100644
--- a/internal/fusefrontend/node_xattr_darwin.go
+++ b/internal/fusefrontend/node_xattr_darwin.go
@@ -6,6 +6,7 @@ import (
 	"golang.org/x/sys/unix"
 
 	"github.com/hanwen/go-fuse/v2/fs"
+	"github.com/hanwen/go-fuse/v2/fuse"
 
 	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
 )
@@ -40,7 +41,7 @@ func (n *Node) getXAttr(cAttr string) (out []byte, errno syscall.Errno) {
 	return cData, 0
 }
 
-func (n *Node) setXAttr(cAttr string, cData []byte, flags uint32) (errno syscall.Errno) {
+func (n *Node) setXAttr(context *fuse.Context, cAttr string, cData []byte, flags uint32) (errno syscall.Errno) {
 	dirfd, cName, errno := n.prepareAtSyscall("")
 	if errno != 0 {
 		return
diff --git a/internal/fusefrontend/node_xattr_linux.go b/internal/fusefrontend/node_xattr_linux.go
index 342bdf6..9698282 100644
--- a/internal/fusefrontend/node_xattr_linux.go
+++ b/internal/fusefrontend/node_xattr_linux.go
@@ -7,6 +7,7 @@ import (
 	"golang.org/x/sys/unix"
 
 	"github.com/hanwen/go-fuse/v2/fs"
+	"github.com/hanwen/go-fuse/v2/fuse"
 
 	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
 )
@@ -30,7 +31,7 @@ func (n *Node) getXAttr(cAttr string) (out []byte, errno syscall.Errno) {
 	return cData, 0
 }
 
-func (n *Node) setXAttr(cAttr string, cData []byte, flags uint32) (errno syscall.Errno) {
+func (n *Node) setXAttr(context *fuse.Context, cAttr string, cData []byte, flags uint32) (errno syscall.Errno) {
 	dirfd, cName, errno := n.prepareAtSyscall("")
 	if errno != 0 {
 		return
@@ -38,7 +39,8 @@ func (n *Node) setXAttr(cAttr string, cData []byte, flags uint32) (errno syscall
 	defer syscall.Close(dirfd)
 
 	procPath := fmt.Sprintf("/proc/self/fd/%d/%s", dirfd, cName)
-	return fs.ToErrno(unix.Lsetxattr(procPath, cAttr, cData, int(flags)))
+
+	return fs.ToErrno(syscallcompat.LsetxattrUser(procPath, cAttr, cData, int(flags), context))
 }
 
 func (n *Node) removeXAttr(cAttr string) (errno syscall.Errno) {