Comment 21 for bug 1857257

Quick fix (not sure that it's fully correct)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 943733d86da3..fa30b615076e 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -24,13 +24,16 @@ static char ovl_whatisit(struct inode *inode, struct inode *realinode)
 static struct file *ovl_open_realfile(const struct file *file,
                                      struct inode *realinode)
 {
+ struct path realpath;
        struct inode *inode = file_inode(file);
        struct file *realfile;
        const struct cred *old_cred;
        int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;

        old_cred = ovl_override_creds(inode->i_sb);
- realfile = open_with_fake_path(&file->f_path, flags, realinode,
+ ovl_path_real(file->f_path.dentry, &realpath);
+ realpath.mnt = file->f_path.mnt; // important!
+ realfile = open_with_fake_path(&realpath, flags, realinode,
                                       current_cred());
        revert_creds(old_cred);