From 029a52ada6a774cac457f3be34b79cfc85563ced Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Thu, 21 Jan 2021 14:19:47 +0100
Subject: [PATCH] overlayfs: do not mount on top of idmapped mounts
Prevent overlayfs 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/20210121131959.646623-29-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/overlayfs/super.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index c04612b1905452..b702c576e7830d 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -858,6 +858,10 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
pr_err("filesystem on '%s' not supported\n", name);
goto out_put;
}
+ if (mnt_user_ns(path->mnt) != &init_user_ns) {
+ pr_err("idmapped layers are currently not supported\n");
+ goto out_put;
+ }
if (!d_is_dir(path->dentry)) {
pr_err("'%s' not a directory\n", name);
goto out_put;
--
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