2 files changed, 27 insertions, 0 deletions
diff --git a/internal/syscallcompat/sys_darwin.go b/internal/syscallcompat/sys_darwin.go
index 7defc5f..3c431b9 100644
--- a/internal/syscallcompat/sys_darwin.go
+++ b/internal/syscallcompat/sys_darwin.go
@@ -79,6 +79,11 @@ func Mkdirat(dirfd int, path string, mode uint32) (err error) {
 	return emulateMkdirat(dirfd, path, mode)
 }
 
+func MkdiratUser(dirfd int, path string, mode uint32, context *fuse.Context) (err error) {
+	// FIXME: take into account context.Owner
+	return Mkdirat(dirfd, path, mode)
+}
+
 func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
 	return emulateFstatat(dirfd, path, stat, flags)
 }
diff --git a/internal/syscallcompat/sys_linux.go b/internal/syscallcompat/sys_linux.go
index 595aa1d..a431195 100644
--- a/internal/syscallcompat/sys_linux.go
+++ b/internal/syscallcompat/sys_linux.go
@@ -180,6 +180,28 @@ func Mkdirat(dirfd int, path string, mode uint32) (err error) {
 	return syscall.Mkdirat(dirfd, path, mode)
 }
 
+// MkdiratUser runs the Mkdirat syscall in the context of a different user.
+func MkdiratUser(dirfd int, path string, mode uint32, context *fuse.Context) (err error) {
+	if context != nil {
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+
+		err = syscall.Setregid(-1, int(context.Owner.Gid))
+		if err != nil {
+			return err
+		}
+		defer syscall.Setregid(-1, 0)
+
+		err = syscall.Setreuid(-1, int(context.Owner.Uid))
+		if err != nil {
+			return err
+		}
+		defer syscall.Setreuid(-1, 0)
+	}
+
+	return Mkdirat(dirfd, path, mode)
+}
+
 // Fstatat syscall.
 func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
 	// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?