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d="scan'208";a="191538498" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jul 2021 08:37:05 -0700 X-IronPort-AV: E=Sophos;i="5.84,255,1620716400"; d="scan'208";a="469799017" Received: from lesliemu-mobl1.amr.corp.intel.com (HELO intel.com) ([10.252.136.56]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jul 2021 08:37:04 -0700 Date: Tue, 20 Jul 2021 08:37:00 -0700 From: Ben Widawsky To: Xiyu Yang Cc: Andrew Morton , Feng Tang , Mike Kravetz , Muchun Song , Yanfei Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, yuanxzhang@fudan.edu.cn, Xin Tan Subject: Re: [PATCH] mm/mempolicy: Convert from atomic_t to refcount_t on mempolicy->refcnt Message-ID: <20210720153700.tqq4d7fronda42ro@intel.com> Mail-Followup-To: Xiyu Yang , Andrew Morton , Feng Tang , Mike Kravetz , Muchun Song , Yanfei Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, yuanxzhang@fudan.edu.cn, Xin Tan References: <1626683671-64407-1-git-send-email-xiyuyang19@fudan.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1626683671-64407-1-git-send-email-xiyuyang19@fudan.edu.cn> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4A3053000105 X-Stat-Signature: g1u1jh9cyi6hap818swuz76tyk18hx4y Authentication-Results: imf09.hostedemail.com; dkim=none; spf=none (imf09.hostedemail.com: domain of ben.widawsky@intel.com has no SPF policy when checking 192.55.52.151) smtp.mailfrom=ben.widawsky@intel.com; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none) X-HE-Tag: 1626795427-429174 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 21-07-19 16:34:28, Xiyu Yang wrote: > refcount_t type and corresponding API can protect refcounters from > accidental underflow and overflow and further use-after-free situations. > > Signed-off-by: Xiyu Yang > Signed-off-by: Xin Tan lgtm Acked-by: Ben Widawsky > --- > include/linux/mempolicy.h | 5 +++-- > mm/mempolicy.c | 8 ++++---- > 2 files changed, 7 insertions(+), 6 deletions(-) > > diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h > index 0aaf91b496e2..faec94994eb7 100644 > --- a/include/linux/mempolicy.h > +++ b/include/linux/mempolicy.h > @@ -6,6 +6,7 @@ > #ifndef _LINUX_MEMPOLICY_H > #define _LINUX_MEMPOLICY_H 1 > > +#include > #include > #include > #include > @@ -43,7 +44,7 @@ struct mm_struct; > * to 1, representing the caller of mpol_dup(). > */ > struct mempolicy { > - atomic_t refcnt; > + refcount_t refcnt; > unsigned short mode; /* See MPOL_* above */ > unsigned short flags; /* See set_mempolicy() MPOL_F_* above */ > nodemask_t nodes; /* interleave/bind/perfer */ > @@ -94,7 +95,7 @@ static inline struct mempolicy *mpol_dup(struct mempolicy *pol) > static inline void mpol_get(struct mempolicy *pol) > { > if (pol) > - atomic_inc(&pol->refcnt); > + refcount_inc(&pol->refcnt); > } > > extern bool __mpol_equal(struct mempolicy *a, struct mempolicy *b); > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index e32360e90274..829a14f34b43 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -298,7 +298,7 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags, > policy = kmem_cache_alloc(policy_cache, GFP_KERNEL); > if (!policy) > return ERR_PTR(-ENOMEM); > - atomic_set(&policy->refcnt, 1); > + refcount_set(&policy->refcnt, 1); > policy->mode = mode; > policy->flags = flags; > > @@ -308,7 +308,7 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags, > /* Slow path of a mpol destructor. */ > void __mpol_put(struct mempolicy *p) > { > - if (!atomic_dec_and_test(&p->refcnt)) > + if (!refcount_dec_and_test(&p->refcnt)) > return; > kmem_cache_free(policy_cache, p); > } > @@ -2290,7 +2290,7 @@ struct mempolicy *__mpol_dup(struct mempolicy *old) > nodemask_t mems = cpuset_mems_allowed(current); > mpol_rebind_policy(new, &mems); > } > - atomic_set(&new->refcnt, 1); > + refcount_set(&new->refcnt, 1); > return new; > } > > @@ -2581,7 +2581,7 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start, > goto alloc_new; > > *mpol_new = *n->policy; > - atomic_set(&mpol_new->refcnt, 1); > + refcount_set(&mpol_new->refcnt, 1); > sp_node_init(n_new, end, n->end, mpol_new); > n->end = start; > sp_insert(sp, n_new); > -- > 2.7.4 >