netdev - [PATCH 31/36] net, sctp: convert sctp_chunk.refcnt from atomic_t to refcount

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Date:   Tue,  4 Jul 2017 15:53:26 +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 31/36] net, sctp: convert sctp_chunk.refcnt 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/sctp/structs.h | 2 +-
 net/sctp/sm_make_chunk.c   | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 4d7c855..0dfc5c1 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -524,7 +524,7 @@ int sctp_chunk_abandoned(struct sctp_chunk *);
 struct sctp_chunk {
 	struct list_head list;
 
-	atomic_t refcnt;
+	refcount_t refcnt;
 
 	/* How many times this chunk have been sent, for prsctp RTX policy */
 	int sent_count;
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 3af4dd0..4e16b02 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1345,7 +1345,7 @@ struct sctp_chunk *sctp_chunkify(struct sk_buff *skb,
 	INIT_LIST_HEAD(&retval->transmitted_list);
 	INIT_LIST_HEAD(&retval->frag_list);
 	SCTP_DBG_OBJCNT_INC(chunk);
-	atomic_set(&retval->refcnt, 1);
+	refcount_set(&retval->refcnt, 1);
 
 nodata:
 	return retval;
@@ -1458,13 +1458,13 @@ void sctp_chunk_free(struct sctp_chunk *chunk)
 /* Grab a reference to the chunk. */
 void sctp_chunk_hold(struct sctp_chunk *ch)
 {
-	atomic_inc(&ch->refcnt);
+	refcount_inc(&ch->refcnt);
 }
 
 /* Release a reference to the chunk. */
 void sctp_chunk_put(struct sctp_chunk *ch)
 {
-	if (atomic_dec_and_test(&ch->refcnt))
+	if (refcount_dec_and_test(&ch->refcnt))
 		sctp_chunk_destroy(ch);
 }
 
-- 
2.7.4