[PATCH 19/29] drivers, s390: convert lcs_reply.refcnt from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:21:06Z

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@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
---
drivers/s390/net/lcs.c | 8 +++-----
drivers/s390/net/lcs.h | 3 ++-
2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index 211b31d..18dc787 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -774,15 +774,13 @@ lcs_get_lancmd(struct lcs_card *card, int count)
static void
lcs_get_reply(struct lcs_reply *reply)
{
- WARN_ON(atomic_read(&reply->refcnt) <= 0);
- atomic_inc(&reply->refcnt);
+ refcount_inc(&reply->refcnt);
}

static void
lcs_put_reply(struct lcs_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);
}

@@ -798,7 +796,7 @@ lcs_alloc_reply(struct lcs_cmd *cmd)
reply = kzalloc(sizeof(struct lcs_reply), GFP_ATOMIC);
if (!reply)
return NULL;
- atomic_set(&reply->refcnt,1);
+ refcount_set(&reply->refcnt,1);
reply->sequence_no = cmd->sequence_no;
reply->received = 0;
reply->rc = 0;
diff --git a/drivers/s390/net/lcs.h b/drivers/s390/net/lcs.h
index 150fcb4..3802f4f 100644
--- a/drivers/s390/net/lcs.h
+++ b/drivers/s390/net/lcs.h
@@ -4,6 +4,7 @@
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/workqueue.h>
+#include <linux/refcount.h>
#include <asm/ccwdev.h>

#define LCS_DBF_TEXT(level, name, text) \
@@ -270,7 +271,7 @@ struct lcs_buffer {
struct lcs_reply {
struct list_head list;
__u16 sequence_no;
- atomic_t refcnt;
+ refcount_t refcnt;
/* Callback for completion notification. */
void (*callback)(struct lcs_card *, struct lcs_cmd *);
wait_queue_head_t wait_q;
--
2.7.4

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