After the previous commit, we do not need to modify the mounter credentials (returned by override_creds()) 'usage' counter when preparing for "create" operations, as 'usage' will be kept constant. Add a warning to verify that we are indeed working with the mounter credentials (stored in the superblock). Failure in this assumption means that creds may leak. Suggested-by: Christian Brauner <brauner@xxxxxxxxxx> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx> --- fs/overlayfs/dir.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 74769d47c8ae..de012db6c169 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -571,7 +571,12 @@ static int ovl_setup_cred_for_create(struct dentry *dentry, struct inode *inode, put_cred(override_cred); return err; } - put_cred(override_creds(override_cred)); + + /* + * We must be called with creator creds already, otherwise we risk + * leaking creds. + */ + WARN_ON_ONCE(override_creds(override_cred) != ovl_creds(dentry->d_sb)); put_cred(override_cred); return 0; -- 2.47.0
