From 0f16ff0f545d5ec90bbd548afd2983785b546780 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Thu, 21 Jan 2021 14:19:46 +0100
Subject: [PATCH] ecryptfs: do not mount on top of idmapped mounts
Prevent ecryptfs from being mounted on top of idmapped mounts.
Stacking filesystems need to be prevented from being mounted on top of
idmapped mounts until they have have been converted to handle this.
Link: https://lore.kernel.org/r/20210121131959.646623-28-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
fs/ecryptfs/main.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index e63259fdef288..cdf40a54a35d8 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -531,6 +531,12 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
goto out_free;
}
+ if (mnt_user_ns(path.mnt) != &init_user_ns) {
+ rc = -EINVAL;
+ printk(KERN_ERR "Mounting on idmapped mounts currently disallowed\n");
+ goto out_free;
+ }
+
if (check_ruid && !uid_eq(d_inode(path.dentry)->i_uid, current_uid())) {
rc = -EPERM;
printk(KERN_ERR "Mount of device (uid: %d) not owned by "
--
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