linux-kernel - [RFC PATCH 5/5] ovl: unprivieged mounts

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Message-Id: <20191025112917.22518-6-mszeredi@redhat.com>
Date:   Fri, 25 Oct 2019 13:29:17 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     "Eric W . Biederman" <ebiederm@...ssion.com>
Cc:     linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH 5/5] ovl: unprivieged mounts

Enable unprivileged user namespace mounts of overlayfs.  Overlayfs's
permission model (*) ensures that the mounter itself cannot gain additional
privileges by the act of creating an overlayfs mount.

This feature request is coming from the "rootless" container crowd.

(*) Documentation/filesystems/overlayfs.txt#Permission model

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 fs/overlayfs/super.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d122c07f2a43..c7f21a049c6b 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1739,6 +1739,7 @@ static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
 static struct file_system_type ovl_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "overlay",
+	.fs_flags	= FS_USERNS_MOUNT,
 	.mount		= ovl_mount,
 	.kill_sb	= kill_anon_super,
 };
-- 
2.21.0