[Xen-devel] [PATCH 20/29] drivers, s390: convert qeth_reply.refcnt from atomic_t to refcount_t

[Elena Reshetova <elena.reshetova@xxxxxxxxx>]

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@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
 drivers/s390/net/qeth_core.h      | 3 ++-
 drivers/s390/net/qeth_core_main.c | 8 +++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index e7addea..e2c81d21 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -20,6 +20,7 @@
 #include <linux/ethtool.h>
 #include <linux/hashtable.h>
 #include <linux/ip.h>
+#include <linux/refcount.h>
 
 #include <net/ipv6.h>
 #include <net/if_inet6.h>
@@ -641,7 +642,7 @@ struct qeth_reply {
        int rc;
        void *param;
        struct qeth_card *card;
-       atomic_t refcnt;
+       refcount_t refcnt;
 };
 
 
diff --git a/drivers/s390/net/qeth_core_main.c 
b/drivers/s390/net/qeth_core_main.c
index 315d8a2..a2bf13f 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -555,7 +555,7 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card 
*card)
 
        reply = kzalloc(sizeof(struct qeth_reply), GFP_ATOMIC);
        if (reply) {
-               atomic_set(&reply->refcnt, 1);
+               refcount_set(&reply->refcnt, 1);
                atomic_set(&reply->received, 0);
                reply->card = card;
        }
@@ -564,14 +564,12 @@ static struct qeth_reply *qeth_alloc_reply(struct 
qeth_card *card)
 
 static void qeth_get_reply(struct qeth_reply *reply)
 {
-       WARN_ON(atomic_read(&reply->refcnt) <= 0);
-       atomic_inc(&reply->refcnt);
+       refcount_inc(&reply->refcnt);
 }
 
 static void qeth_put_reply(struct qeth_reply *reply)
 {
-       WARN_ON(atomic_read(&reply->refcnt) <= 0);
-       if (atomic_dec_and_test(&reply->refcnt))
+       if (refcount_dec_and_test(&reply->refcnt))
                kfree(reply);
 }
 
-- 
2.7.4


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