netdev - [PATCH 06/18] net, decnet: convert dn_fib_info.fib_clntref from atomic_t to refcount

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Date:   Fri, 17 Mar 2017 13:12:47 +0200
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, linux-bluetooth@...r.kernel.org,
        marcel@...tmann.org, johan.hedberg@...il.com, peterz@...radead.org,
        keescook@...omium.org, Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 06/18] net, decnet: convert dn_fib_info.fib_clntref 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>
---
 include/net/dn_fib.h | 5 +++--
 net/decnet/dn_fib.c  | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/net/dn_fib.h b/include/net/dn_fib.h
index f2ca135..81210a8 100644
--- a/include/net/dn_fib.h
+++ b/include/net/dn_fib.h
@@ -2,6 +2,7 @@
 #define _NET_DN_FIB_H
 
 #include <linux/netlink.h>
+#include <linux/refcount.h>
 
 extern const struct nla_policy rtm_dn_policy[];
 
@@ -28,7 +29,7 @@ struct dn_fib_info {
 	struct dn_fib_info	*fib_next;
 	struct dn_fib_info	*fib_prev;
 	int 			fib_treeref;
-	atomic_t		fib_clntref;
+	refcount_t		fib_clntref;
 	int			fib_dead;
 	unsigned int		fib_flags;
 	int			fib_protocol;
@@ -130,7 +131,7 @@ void dn_fib_free_info(struct dn_fib_info *fi);
 
 static inline void dn_fib_info_put(struct dn_fib_info *fi)
 {
-	if (atomic_dec_and_test(&fi->fib_clntref))
+	if (refcount_dec_and_test(&fi->fib_clntref))
 		dn_fib_free_info(fi);
 }
 
diff --git a/net/decnet/dn_fib.c b/net/decnet/dn_fib.c
index 7af0ba61..85058c3 100644
--- a/net/decnet/dn_fib.c
+++ b/net/decnet/dn_fib.c
@@ -389,7 +389,7 @@ struct dn_fib_info *dn_fib_create_info(const struct rtmsg *r, struct nlattr *att
 	}
 
 	fi->fib_treeref++;
-	atomic_inc(&fi->fib_clntref);
+	refcount_set(&fi->fib_clntref, 1);
 	spin_lock(&dn_fib_info_lock);
 	fi->fib_next = dn_fib_info_list;
 	fi->fib_prev = NULL;
@@ -425,7 +425,7 @@ int dn_fib_semantic_match(int type, struct dn_fib_info *fi, const struct flowidn
 		switch (type) {
 		case RTN_NAT:
 			DN_FIB_RES_RESET(*res);
-			atomic_inc(&fi->fib_clntref);
+			refcount_inc(&fi->fib_clntref);
 			return 0;
 		case RTN_UNICAST:
 		case RTN_LOCAL:
@@ -438,7 +438,7 @@ int dn_fib_semantic_match(int type, struct dn_fib_info *fi, const struct flowidn
 			}
 			if (nhsel < fi->fib_nhs) {
 				res->nh_sel = nhsel;
-				atomic_inc(&fi->fib_clntref);
+				refcount_inc(&fi->fib_clntref);
 				return 0;
 			}
 			endfor_nexthops(fi);
-- 
2.7.4