From 029a52ada6a774cac457f3be34b79cfc85563ced Mon Sep 17 00:00:00 2001 From: Christian Brauner 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 Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: James Morris Signed-off-by: Christian Brauner --- fs/overlayfs/super.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index c04612b19054..b702c576e783 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;