[PATCH 0/3] s390 refcount conversions

[PATCH 0/3] s390 refcount conversions

[Elena Reshetova]

This series, for S390, replaces atomic_t reference
counters with the new refcount_t type and API (see include/linux/refcount.h).
By doing this we prevent intentional or accidental
underflows or overflows that can led to use-after-free vulnerabilities.

The patches are fully independent and can be cherry-picked separately.
Patches are based on top of linux-next as of yesterday.
If there are no objections to the patches, please merge them via respective trees

Elena Reshetova (3):
  [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t
  [S390] net: convert lcs_reply.refcnt from atomic_t to refcount_t
  [S390] qeth: convert qeth_reply.refcnt from atomic_t to refcount_t

 drivers/s390/char/vmur.c          |  8 ++++----
 drivers/s390/char/vmur.h          |  4 +++-
 drivers/s390/net/lcs.c            | 10 +++++-----
 drivers/s390/net/lcs.h            |  3 ++-
 drivers/s390/net/qeth_core.h      |  3 ++-
 drivers/s390/net/qeth_core_main.c | 10 +++++-----
 6 files changed, 21 insertions(+), 17 deletions(-)

-- 
2.7.4

[PATCH 1/3] [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t

[Elena Reshetova]

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 urdev.ref_count 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>
---
 drivers/s390/char/vmur.c | 8 ++++----
 drivers/s390/char/vmur.h | 4 +++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/char/vmur.c b/drivers/s390/char/vmur.c
index 04aceb6..ced8151 100644
--- a/drivers/s390/char/vmur.c
+++ b/drivers/s390/char/vmur.c
@@ -110,7 +110,7 @@ static struct urdev *urdev_alloc(struct ccw_device *cdev)
 	mutex_init(&urd->io_mutex);
 	init_waitqueue_head(&urd->wait);
 	spin_lock_init(&urd->open_lock);
-	atomic_set(&urd->ref_count,  1);
+	refcount_set(&urd->ref_count,  1);
 	urd->cdev = cdev;
 	get_device(&cdev->dev);
 	return urd;
@@ -126,7 +126,7 @@ static void urdev_free(struct urdev *urd)
 
 static void urdev_get(struct urdev *urd)
 {
-	atomic_inc(&urd->ref_count);
+	refcount_inc(&urd->ref_count);
 }
 
 static struct urdev *urdev_get_from_cdev(struct ccw_device *cdev)
@@ -159,7 +159,7 @@ static struct urdev *urdev_get_from_devno(u16 devno)
 
 static void urdev_put(struct urdev *urd)
 {
-	if (atomic_dec_and_test(&urd->ref_count))
+	if (refcount_dec_and_test(&urd->ref_count))
 		urdev_free(urd);
 }
 
@@ -946,7 +946,7 @@ static int ur_set_offline_force(struct ccw_device *cdev, int force)
 		rc = -EBUSY;
 		goto fail_urdev_put;
 	}
-	if (!force && (atomic_read(&urd->ref_count) > 2)) {
+	if (!force && (refcount_read(&urd->ref_count) > 2)) {
 		/* There is still a user of urd (e.g. ur_open) */
 		TRACE("ur_set_offline: BUSY\n");
 		rc = -EBUSY;
diff --git a/drivers/s390/char/vmur.h b/drivers/s390/char/vmur.h
index fa320ad..35ea9d1 100644
--- a/drivers/s390/char/vmur.h
+++ b/drivers/s390/char/vmur.h
@@ -11,6 +11,8 @@
 #ifndef _VMUR_H_
 #define _VMUR_H_
 
+#include <linux/refcount.h>
+
 #define DEV_CLASS_UR_I 0x20 /* diag210 unit record input device class */
 #define DEV_CLASS_UR_O 0x10 /* diag210 unit record output device class */
 /*
@@ -69,7 +71,7 @@ struct urdev {
 	size_t reclen;			/* Record length for *write* CCWs */
 	int class;			/* VM device class */
 	int io_request_rc;		/* return code from I/O request */
-	atomic_t ref_count;		/* reference counter */
+	refcount_t ref_count;		/* reference counter */
 	wait_queue_head_t wait;		/* wait queue to serialize open */
 	int open_flag;			/* "urdev is open" flag */
 	spinlock_t open_lock;		/* serialize critical sections */
-- 
2.7.4

Re: [PATCH 1/3] [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t

[Martin Schwidefsky]

On Fri, 20 Oct 2017 10:47:48 +0300
Elena Reshetova <elena.reshetova@intel.com> wrote:

> 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 urdev.ref_count 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>

Added to s390/linux:features for the next merge window. Thanks.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

RE: [PATCH 1/3] [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t

[Reshetova, Elena]

> On Fri, 20 Oct 2017 10:47:48 +0300
> Elena Reshetova <elena.reshetova@intel.com> wrote:
> 
> > 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 urdev.ref_count 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>
> 
> Added to s390/linux:features for the next merge window. Thanks.

Thank you very much!

Best Regards,
Elena.
> 
> --
> blue skies,
>    Martin.
> 
> "Reality continues to ruin my life." - Calvin.

[PATCH 2/3] [S390] net: convert lcs_reply.refcnt from atomic_t to refcount_t

[Elena Reshetova]

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@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>
---
 drivers/s390/net/lcs.c | 10 +++++-----
 drivers/s390/net/lcs.h |  3 ++-
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index d01b5c2..d7344be 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -769,15 +769,15 @@ 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);
+	WARN_ON(refcount_read(&reply->refcnt) == 0);
+	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)) {
+		WARN_ON(refcount_read(&reply->refcnt) == 0);
+		if (refcount_dec_and_test(&reply->refcnt)) {
 		kfree(reply);
 	}
 
@@ -793,7 +793,7 @@ 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

[PATCH 3/3] [S390] qeth: convert qeth_reply.refcnt from atomic_t to refcount_t

[Elena Reshetova]

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>
---
 drivers/s390/net/qeth_core.h      |  3 ++-
 drivers/s390/net/qeth_core_main.c | 10 +++++-----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index 91fcadb..49ba742 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -20,6 +20,7 @@
 #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>
@@ -645,7 +646,7 @@ struct qeth_reply {
 	int rc;
 	void *param;
 	struct qeth_card *card;
-	atomic_t refcnt;
+	refcount_t refcnt;
 };
 
 struct qeth_card_blkt {
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 68e118f..86e4c5d 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -559,7 +559,7 @@ 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;
 	}
@@ -568,14 +568,14 @@ 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);
+	WARN_ON(refcount_read(&reply->refcnt) == 0);
+	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))
+	WARN_ON(refcount_read(&reply->refcnt) == 0);
+	if (refcount_dec_and_test(&reply->refcnt))
 		kfree(reply);
 }
 
-- 
2.7.4

Re: [PATCH 0/3] s390 refcount conversions

[Julian Wiedmann]

On 10/20/2017 09:47 AM, Elena Reshetova wrote:
> This series, for S390, replaces atomic_t reference
> counters with the new refcount_t type and API (see include/linux/refcount.h).
> By doing this we prevent intentional or accidental
> underflows or overflows that can led to use-after-free vulnerabilities.
> 
> The patches are fully independent and can be cherry-picked separately.
> Patches are based on top of linux-next as of yesterday.
> If there are no objections to the patches, please merge them via respective trees
> 
> Elena Reshetova (3):
>   [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t
>   [S390] net: convert lcs_reply.refcnt from atomic_t to refcount_t
>   [S390] qeth: convert qeth_reply.refcnt from atomic_t to refcount_t
> 
>  drivers/s390/char/vmur.c          |  8 ++++----
>  drivers/s390/char/vmur.h          |  4 +++-
>  drivers/s390/net/lcs.c            | 10 +++++-----
>  drivers/s390/net/lcs.h            |  3 ++-
>  drivers/s390/net/qeth_core.h      |  3 ++-
>  drivers/s390/net/qeth_core_main.c | 10 +++++-----
>  6 files changed, 21 insertions(+), 17 deletions(-)
> 
Thanks Elena, I picked up the two network patches. Also removed the WARN_ONs while applying,
those who care may use CONFIG_REFCOUNT_FULL.

RE: [PATCH 0/3] s390 refcount conversions

[Reshetova, Elena]

> On 10/20/2017 09:47 AM, Elena Reshetova wrote:
> > This series, for S390, replaces atomic_t reference
> > counters with the new refcount_t type and API (see include/linux/refcount.h).
> > By doing this we prevent intentional or accidental
> > underflows or overflows that can led to use-after-free vulnerabilities.
> >
> > The patches are fully independent and can be cherry-picked separately.
> > Patches are based on top of linux-next as of yesterday.
> > If there are no objections to the patches, please merge them via respective trees
> >
> > Elena Reshetova (3):
> >   [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t
> >   [S390] net: convert lcs_reply.refcnt from atomic_t to refcount_t
> >   [S390] qeth: convert qeth_reply.refcnt from atomic_t to refcount_t
> >
> >  drivers/s390/char/vmur.c          |  8 ++++----
> >  drivers/s390/char/vmur.h          |  4 +++-
> >  drivers/s390/net/lcs.c            | 10 +++++-----
> >  drivers/s390/net/lcs.h            |  3 ++-
> >  drivers/s390/net/qeth_core.h      |  3 ++-
> >  drivers/s390/net/qeth_core_main.c | 10 +++++-----
> >  6 files changed, 21 insertions(+), 17 deletions(-)
> >
> Thanks Elena, I picked up the two network patches. Also removed the WARN_ONs
> while applying,
> those who care may use CONFIG_REFCOUNT_FULL.

Thank you Julian! I had them first removed also, but since we got x86 that doesn't 
WARN in these cases, I put them back just to make sure I don't make any
unexpected changes.  

Do you know who would be the correct person to take the last patch? 

Best Regards,
Elena