netdev - [PATCH 23/36] net, rds: convert rds_message.m_refcount from atomic_t to refcount

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Date:   Tue,  4 Jul 2017 15:53:18 +0300
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        linux-decnet-user@...ts.sourceforge.net, davem@...emloft.net,
        jmorris@...ei.org, kaber@...sh.net, yoshfuji@...ux-ipv6.org,
        kuznet@....inr.ac.ru, 3chas3@...il.com, ralf@...ux-mips.org,
        stephen@...workplumber.org, jchapman@...alix.com, jhs@...atatu.com,
        bridge@...ts.linux-foundation.org, linux-hams@...r.kernel.org,
        linux-x25@...r.kernel.org, peterz@...radead.org,
        keescook@...omium.org, linux-rdma@...r.kernel.org,
        linux-sctp@...r.kernel.org, vyasevich@...il.com,
        nhorman@...driver.com, linux-nfs@...r.kernel.org, zyan@...hat.com,
        sage@...hat.com, bfields@...ldses.org, jlayton@...chiereds.net,
        steffen.klassert@...unet.com, herbert@...dor.apana.org.au,
        santosh.shilimkar@...cle.com, jreuter@...na.de,
        Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 23/36] net, rds: convert rds_message.m_refcount from atomic_t to refcount_t

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 <elena.reshetova@...el.com>
Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David Windsor <dwindsor@...il.com>
---
 net/rds/message.c | 12 ++++++------
 net/rds/rds.h     |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/rds/message.c b/net/rds/message.c
index 49bfb51..4318cc9 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -48,8 +48,8 @@ static unsigned int	rds_exthdr_size[__RDS_EXTHDR_MAX] = {
 
 void rds_message_addref(struct rds_message *rm)
 {
-	rdsdebug("addref rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
-	atomic_inc(&rm->m_refcount);
+	rdsdebug("addref rm %p ref %d\n", rm, refcount_read(&rm->m_refcount));
+	refcount_inc(&rm->m_refcount);
 }
 EXPORT_SYMBOL_GPL(rds_message_addref);
 
@@ -83,9 +83,9 @@ static void rds_message_purge(struct rds_message *rm)
 
 void rds_message_put(struct rds_message *rm)
 {
-	rdsdebug("put rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
-	WARN(!atomic_read(&rm->m_refcount), "danger refcount zero on %p\n", rm);
-	if (atomic_dec_and_test(&rm->m_refcount)) {
+	rdsdebug("put rm %p ref %d\n", rm, refcount_read(&rm->m_refcount));
+	WARN(!refcount_read(&rm->m_refcount), "danger refcount zero on %p\n", rm);
+	if (refcount_dec_and_test(&rm->m_refcount)) {
 		BUG_ON(!list_empty(&rm->m_sock_item));
 		BUG_ON(!list_empty(&rm->m_conn_item));
 		rds_message_purge(rm);
@@ -206,7 +206,7 @@ struct rds_message *rds_message_alloc(unsigned int extra_len, gfp_t gfp)
 	rm->m_used_sgs = 0;
 	rm->m_total_sgs = extra_len / sizeof(struct scatterlist);
 
-	atomic_set(&rm->m_refcount, 1);
+	refcount_set(&rm->m_refcount, 1);
 	INIT_LIST_HEAD(&rm->m_sock_item);
 	INIT_LIST_HEAD(&rm->m_conn_item);
 	spin_lock_init(&rm->m_rs_lock);
diff --git a/net/rds/rds.h b/net/rds/rds.h
index ea72d6e..516bcc8 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -356,7 +356,7 @@ static inline u32 rds_rdma_cookie_offset(rds_rdma_cookie_t cookie)
 #define RDS_MSG_FLUSH		8
 
 struct rds_message {
-	atomic_t		m_refcount;
+	refcount_t		m_refcount;
 	struct list_head	m_sock_item;
 	struct list_head	m_conn_item;
 	struct rds_incoming	m_inc;
-- 
2.7.4