[PATCH v3 35/38] overlayfs: do not mount on top of idmapped mounts

Christian Brauner
2020-11-28T22:10:32Z

Prevent overlayfs from being mounted on top of idmapped mounts until we
have ported it to handle this case and added proper testing for it.

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
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
patch introduced

/* v3 */
- Amir Goldstein <amir73il@gmail.com>:
- Move check for idmapped lower layers into ovl_mount_dir_noesc().
- David Howells <dhowells@redhat.com>:
- Adapt check after removing mnt_idmapped() helper.
---
fs/overlayfs/super.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 0d4f2baf6836..5002f97b01e6 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -811,6 +811,10 @@ 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;
--
2.29.2