[PATCH v2 36/39] overlayfs: do not mount on top of idmapped mounts

Christian Brauner
2020-11-16T02:15:33Z

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
---
fs/overlayfs/super.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 0d4f2baf6836..3cacc3d3fb65 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1708,6 +1708,12 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
if (err)
goto out_err;

+ if (mnt_idmapped(stack[i].mnt)) {
+ err = -EINVAL;
+ pr_err("idmapped lower layers are currently unsupported\n");
+ goto out_err;
+ }
+
lower = strchr(lower, '\0') + 1;
}

@@ -1939,6 +1945,12 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (err)
goto out_err;

+ if (mnt_idmapped(upperpath.mnt)) {
+ err = -EINVAL;
+ pr_err("idmapped lower layers are currently unsupported\n");
+ goto out_err;
+ }
+
err = ovl_get_workdir(sb, ofs, &upperpath);
if (err)
goto out_err;