linux-kernel - [PATCH 21/36] net, rds: convert rds_incoming.i_refcount from atomic_t to refcount

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Date:   Tue,  4 Jul 2017 15:53:16 +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 21/36] net, rds: convert rds_incoming.i_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/rds.h  |  3 ++-
 net/rds/recv.c | 12 ++++++------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/rds/rds.h b/net/rds/rds.h
index 4a25db7..35ceaa2 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -8,6 +8,7 @@
 #include <linux/mutex.h>
 #include <linux/rds.h>
 #include <linux/rhashtable.h>
+#include <linux/refcount.h>
 
 #include "info.h"
 
@@ -261,7 +262,7 @@ struct rds_ext_header_rdma_dest {
 #define	RDS_MSG_RX_CMSG		3
 
 struct rds_incoming {
-	atomic_t		i_refcount;
+	refcount_t		i_refcount;
 	struct list_head	i_item;
 	struct rds_connection	*i_conn;
 	struct rds_conn_path	*i_conn_path;
diff --git a/net/rds/recv.c b/net/rds/recv.c
index 373a6aa1..b25bcfe 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -45,7 +45,7 @@ void rds_inc_init(struct rds_incoming *inc, struct rds_connection *conn,
 {
 	int i;
 
-	atomic_set(&inc->i_refcount, 1);
+	refcount_set(&inc->i_refcount, 1);
 	INIT_LIST_HEAD(&inc->i_item);
 	inc->i_conn = conn;
 	inc->i_saddr = saddr;
@@ -61,7 +61,7 @@ EXPORT_SYMBOL_GPL(rds_inc_init);
 void rds_inc_path_init(struct rds_incoming *inc, struct rds_conn_path *cp,
 		       __be32 saddr)
 {
-	atomic_set(&inc->i_refcount, 1);
+	refcount_set(&inc->i_refcount, 1);
 	INIT_LIST_HEAD(&inc->i_item);
 	inc->i_conn = cp->cp_conn;
 	inc->i_conn_path = cp;
@@ -74,14 +74,14 @@ EXPORT_SYMBOL_GPL(rds_inc_path_init);
 
 static void rds_inc_addref(struct rds_incoming *inc)
 {
-	rdsdebug("addref inc %p ref %d\n", inc, atomic_read(&inc->i_refcount));
-	atomic_inc(&inc->i_refcount);
+	rdsdebug("addref inc %p ref %d\n", inc, refcount_read(&inc->i_refcount));
+	refcount_inc(&inc->i_refcount);
 }
 
 void rds_inc_put(struct rds_incoming *inc)
 {
-	rdsdebug("put inc %p ref %d\n", inc, atomic_read(&inc->i_refcount));
-	if (atomic_dec_and_test(&inc->i_refcount)) {
+	rdsdebug("put inc %p ref %d\n", inc, refcount_read(&inc->i_refcount));
+	if (refcount_dec_and_test(&inc->i_refcount)) {
 		BUG_ON(!list_empty(&inc->i_item));
 
 		inc->i_conn->c_trans->inc_free(inc);
-- 
2.7.4