Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753730AbdCTJio (ORCPT ); Mon, 20 Mar 2017 05:38:44 -0400 Received: from mga04.intel.com ([192.55.52.120]:37896 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753404AbdCTJhh (ORCPT ); Mon, 20 Mar 2017 05:37:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,193,1486454400"; d="scan'208";a="238201945" From: Elena Reshetova To: daniel@iogearbox.net Cc: ast@fb.com, linux-kernel@vger.kernel.org, peterz@infradead.org, netdev@vger.kernel.org, Elena Reshetova , Hans Liljestrand , Kees Cook , David Windsor Subject: [PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t Date: Mon, 20 Mar 2017 11:37:21 +0200 Message-Id: <1490002641-10498-1-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2759 Lines: 96 refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Signed-off-by: Elena Reshetova Signed-off-by: Hans Liljestrand Signed-off-by: Kees Cook Signed-off-by: David Windsor --- include/linux/filter.h | 3 ++- net/core/filter.c | 17 ++++++++++++----- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 8053c38..20247e7 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -7,6 +7,7 @@ #include #include +#include #include #include #include @@ -431,7 +432,7 @@ struct bpf_prog { }; struct sk_filter { - atomic_t refcnt; + refcount_t refcnt; struct rcu_head rcu; struct bpf_prog *prog; }; diff --git a/net/core/filter.c b/net/core/filter.c index ebaeaf2..389cb8d 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -928,7 +928,7 @@ static void sk_filter_release_rcu(struct rcu_head *rcu) */ static void sk_filter_release(struct sk_filter *fp) { - if (atomic_dec_and_test(&fp->refcnt)) + if (refcount_dec_and_test(&fp->refcnt)) call_rcu(&fp->rcu, sk_filter_release_rcu); } @@ -943,20 +943,27 @@ void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp) /* try to charge the socket memory if there is space available * return true on success */ -bool sk_filter_charge(struct sock *sk, struct sk_filter *fp) +bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp) { u32 filter_size = bpf_prog_size(fp->prog->len); /* same check as in sock_kmalloc() */ if (filter_size <= sysctl_optmem_max && atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) { - atomic_inc(&fp->refcnt); atomic_add(filter_size, &sk->sk_omem_alloc); return true; } return false; } +bool sk_filter_charge(struct sock *sk, struct sk_filter *fp) +{ + bool ret = __sk_filter_charge(sk, fp); + if (ret) + refcount_inc(&fp->refcnt); + return ret; +} + static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp) { struct sock_filter *old_prog; @@ -1179,12 +1186,12 @@ static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk) return -ENOMEM; fp->prog = prog; - atomic_set(&fp->refcnt, 0); - if (!sk_filter_charge(sk, fp)) { + if (!__sk_filter_charge(sk, fp)) { kfree(fp); return -ENOMEM; } + refcount_set(&fp->refcnt, 1); old_fp = rcu_dereference_protected(sk->sk_filter, lockdep_sock_is_held(sk)); -- 2.7.4