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Commit c380cd5a authored by Elena Reshetova's avatar Elena Reshetova Committed by David S. Miller
Browse files

net: convert lcs_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 lcs_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 a943e8bc

drivers/s390/net/lcs.c

+3 −7
Original line number Diff line number Diff line
@@ -756,20 +756,16 @@ 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 *

lcs_alloc_reply(struct lcs_cmd *cmd)

{
@@ -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;

drivers/s390/net/lcs.h

+2 −1
Original line number Diff line number Diff line
@@ -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;