From: Elena Reshetova <elena.reshetova@xxxxxxxxx>
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable lcs_reply.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
[jwi: removed the WARN_ONs. Use CONFIG_REFCOUNT_FULL if you care.]
Signed-off-by: Julian Wiedmann <jwi@xxxxxxxxxxxxxxxxxx>
---
drivers/s390/net/lcs.c | 10 +++-------
drivers/s390/net/lcs.h | 3 ++-
2 files changed, 5 insertions(+), 8 deletions(-)
diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index 92ae84a927fc..0ee8f33efb54 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -756,18 +756,14 @@ 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);
- }
-
}
static struct lcs_reply *
@@ -780,7 +776,7 @@ 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 fbc8b90b1f85..bd52caa3b11b 100644
--- a/drivers/s390/net/lcs.h
+++ b/drivers/s390/net/lcs.h
@@ -5,6 +5,7 @@
#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) \
@@ -271,7 +272,7 @@ 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;
--
2.13.5
--
To unsubscribe from this list: send the line "unsubscribe linux-s390" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
