From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 28 Jan 2021 09:22:48 +0000 (+0100)
Subject: ovl: add warning on user_ns mismatch
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9efb069de4ba748d284f6129e71de239f801053a;p=linux.git

ovl: add warning on user_ns mismatch

Currently there's no way to create an overlay filesystem outside of the
current user namespace.  Make sure that if this assumption changes it
doesn't go unnoticed.

Reported-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 2bd570cbe8a45..82cd6d55a5a13 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1923,6 +1923,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	unsigned int numlower;
 	int err;
 
+	err = -EIO;
+	if (WARN_ON(sb->s_user_ns != current_user_ns()))
+		goto out;
+
 	sb->s_d_op = &ovl_dentry_operations;
 
 	err = -ENOMEM;