Return-Path: Received: from mga02.intel.com ([134.134.136.20]:31574 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657AbdJTJzp (ORCPT ); Fri, 20 Oct 2017 05:55:45 -0400 From: Elena Reshetova To: trond.myklebust@primarydata.com Cc: linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, anna.schumaker@netapp.com, bfields@fieldses.org, jlayton@poochiereds.net, peterz@infradead.org, keescook@chromium.org, Elena Reshetova Subject: [PATCH 02/11] fs, nfsd: convert nfs4_cntl_odstate.co_odcount from atomic_t to refcount_t Date: Fri, 20 Oct 2017 12:53:29 +0300 Message-Id: <1508493218-27760-3-git-send-email-elena.reshetova@intel.com> In-Reply-To: <1508493218-27760-1-git-send-email-elena.reshetova@intel.com> References: <1508493218-27760-1-git-send-email-elena.reshetova@intel.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nfs4_cntl_odstate.co_odcount is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova --- fs/nfsd/nfs4state.c | 6 +++--- fs/nfsd/state.h | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index d356b87..fb61d79 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -568,7 +568,7 @@ alloc_clnt_odstate(struct nfs4_client *clp) co = kmem_cache_zalloc(odstate_slab, GFP_KERNEL); if (co) { co->co_client = clp; - atomic_set(&co->co_odcount, 1); + refcount_set(&co->co_odcount, 1); } return co; } @@ -586,7 +586,7 @@ static inline void get_clnt_odstate(struct nfs4_clnt_odstate *co) { if (co) - atomic_inc(&co->co_odcount); + refcount_inc(&co->co_odcount); } static void @@ -598,7 +598,7 @@ put_clnt_odstate(struct nfs4_clnt_odstate *co) return; fp = co->co_file; - if (atomic_dec_and_lock(&co->co_odcount, &fp->fi_lock)) { + if (refcount_dec_and_lock(&co->co_odcount, &fp->fi_lock)) { list_del(&co->co_perfile); spin_unlock(&fp->fi_lock); diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index f927aa4..58eb5f4 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -466,7 +466,7 @@ struct nfs4_clnt_odstate { struct nfs4_client *co_client; struct nfs4_file *co_file; struct list_head co_perfile; - atomic_t co_odcount; + refcount_t co_odcount; }; /* -- 2.7.4