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Commit ae695927 authored by Elena Reshetova's avatar Elena Reshetova Committed by David S. Miller
Browse files

qeth: convert qeth_reply.refcnt from atomic_t to refcount_t 



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 qeth_reply.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

Suggested-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarDavid Windsor <dwindsor@gmail.com>
Reviewed-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarElena Reshetova <elena.reshetova@intel.com>
[jwi: removed the WARN_ONs. Use CONFIG_REFCOUNT_FULL if you care.]
Signed-off-by: default avatarJulian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c380cd5a

drivers/s390/net/qeth_core.h

+2 −1
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#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>
@@ -632,7 +633,7 @@ struct qeth_reply { 
	int rc;

	void *param;

	struct qeth_card *card;

	atomic_t refcnt;

	refcount_t refcnt;

};



struct qeth_card_blkt {

drivers/s390/net/qeth_core_main.c

+3 −5
Original line number Diff line number Diff line
@@ -564,7 +564,7 @@ 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;

	}
@@ -573,14 +573,12 @@ 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);

}