fusefrontend: -allow_other: Use MknodatUser in Mknod FUSE call.

Instead of manually adjusting the user and mode after creating the
device file, adjust effective permissions and let the kernel deal
with it.

Related to https://github.com/rfjakob/gocryptfs/issues/338.

1 files changed, 7 insertions, 14 deletions

diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index 2c6ac5a..9637acf 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -319,6 +319,10 @@ func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context)
 		return fuse.ToStatus(err)
 	}
 	defer syscall.Close(dirfd)
+	// Make sure context is nil if we don't want to preserve the owner
+	if !fs.args.PreserveOwner {
+		context = nil
+	}
 	// Create ".name" file to store long file name (except in PlaintextNames mode)
 	if !fs.args.PlaintextNames && nametransform.IsLongContent(cName) {
 		err = fs.nameTransform.WriteLongNameAt(dirfd, cName, path)
@@ -326,26 +330,15 @@ func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context)
 			return fuse.ToStatus(err)
 		}
 		// Create "gocryptfs.longfile." device node
-		err = syscallcompat.Mknodat(dirfd, cName, mode, int(dev))
+		err = syscallcompat.MknodatUser(dirfd, cName, mode, int(dev), context)
 		if err != nil {
 			nametransform.DeleteLongNameAt(dirfd, cName)
 		}
 	} else {
 		// Create regular device node
-		err = syscallcompat.Mknodat(dirfd, cName, mode, int(dev))
-	}
-	if err != nil {
-		return fuse.ToStatus(err)
-	}
-	// Set owner
-	if fs.args.PreserveOwner {
-		err = syscallcompat.Fchownat(dirfd, cName, int(context.Owner.Uid),
-			int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
-		if err != nil {
-			tlog.Warn.Printf("Mknod: Fchownat failed: %v", err)
-		}
+		err = syscallcompat.MknodatUser(dirfd, cName, mode, int(dev), context)
 	}
-	return fuse.OK
+	return fuse.ToStatus(err)
 }
 
 // Truncate - FUSE call. Truncates a file.