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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: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
[jwi: removed the WARN_ONs. Use CONFIG_REFCOUNT_FULL if you care.]
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Elena Reshetova 2017-12-20 20:10:56 +01:00 committed by David S. Miller
parent c380cd5a00
commit ae6959273a
2 changed files with 5 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/s390/net/qeth_core.h
View File

@ -21,6 +21,7 @@
#include <linux/ethtool.h> #include <linux/ethtool.h>
#include <linux/hashtable.h> #include <linux/hashtable.h>
#include <linux/ip.h> #include <linux/ip.h>
#include <linux/refcount.h>
#include <net/ipv6.h> #include <net/ipv6.h>
#include <net/if_inet6.h> #include <net/if_inet6.h>
@ -632,7 +633,7 @@ struct qeth_reply {
int rc; int rc;
void *param; void *param;
struct qeth_card *card; struct qeth_card *card;
atomic_t refcnt; refcount_t refcnt;
}; };
struct qeth_card_blkt { struct qeth_card_blkt {

8
drivers/s390/net/qeth_core_main.c
View File

@ -564,7 +564,7 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card *card)
reply = kzalloc(sizeof(struct qeth_reply), GFP_ATOMIC); reply = kzalloc(sizeof(struct qeth_reply), GFP_ATOMIC);
if (reply) { if (reply) {
atomic_set(&reply->refcnt, 1); refcount_set(&reply->refcnt, 1);
atomic_set(&reply->received, 0); atomic_set(&reply->received, 0);
reply->card = card; 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) static void qeth_get_reply(struct qeth_reply *reply)
{ {
WARN_ON(atomic_read(&reply->refcnt) <= 0); refcount_inc(&reply->refcnt);
atomic_inc(&reply->refcnt);
} }
static void qeth_put_reply(struct qeth_reply *reply) static void qeth_put_reply(struct qeth_reply *reply)
{ {
WARN_ON(atomic_read(&reply->refcnt) <= 0); if (refcount_dec_and_test(&reply->refcnt))
if (atomic_dec_and_test(&reply->refcnt))
kfree(reply); kfree(reply);
} }