netdev - Re: [RFC][PATCH] nfsd: add +1 to reference counting scheme for struct nfsd4

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Date:   Sat, 11 Feb 2017 01:42:53 -0500
From:   David Windsor <dwindsor@...il.com>
To:     linux-nfs@...r.kernel.org, netdev@...r.kernel.org
Cc:     kernel-hardening@...ts.openwall.com,
        Bruce Fields <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Kees Cook <keescook@...omium.org>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        David Windsor <dwindsor@...il.com>
Subject: Re: [RFC][PATCH] nfsd: add +1 to reference counting scheme for struct nfsd4_session

<snip>

> Signed-off-by: David Windsor <dwindsor@...il.com>
> ---
>  fs/nfsd/nfs4state.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index a0dee8a..b0f3010 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -196,7 +196,7 @@ static void nfsd4_put_session_locked(struct nfsd4_session *ses)
>
>         lockdep_assert_held(&nn->client_lock);
>
> -       if (atomic_dec_and_test(&ses->se_ref) && is_session_dead(ses))
> +       if (!atomic_add_unless(&ses->se_ref, -1, 1) && is_session_des(ses))

This should read:
if (!atomic_add_unless(&ses->se_ref, -1, 1) && is_session_dead(ses))

>                 free_session(ses);
>         put_client_renew_locked(clp);
>  }
> @@ -1645,7 +1645,7 @@ static void init_session(struct svc_rqst *rqstp, struct nfsd4_session *new, stru
>         new->se_flags = cses->flags;
>         new->se_cb_prog = cses->callback_prog;
>         new->se_cb_sec = cses->cb_sec;
> -       atomic_set(&new->se_ref, 0);
> +       atomic_set(&new->se_ref, 1);
>         idx = hash_sessionid(&new->se_sessionid);
>         list_add(&new->se_hash, &nn->sessionid_hashtbl[idx]);
>         spin_lock(&clp->cl_lock);
> @@ -1792,7 +1792,7 @@ free_client(struct nfs4_client *clp)
>                 ses = list_entry(clp->cl_sessions.next, struct nfsd4_session,
>                                 se_perclnt);
>                 list_del(&ses->se_perclnt);
> -               WARN_ON_ONCE(atomic_read(&ses->se_ref));
> +               WARN_ON_ONCE((atomic_read(&ses->se_ref) > 1));
>                 free_session(ses);
>         }
>         rpc_destroy_wait_queue(&clp->cl_cb_waitq);
> --
> 2.7.4
>