[PATCH v3 1/3] Bluetooth: bnep: fix possible might sleep error in bnep_session

It looks like bnep_session has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <redacted>
Reviewed-by: Brian Norris <briannorris@chromium.org>
---

Changes in v3:
Add brian's Reviewed-by.

Changes in v2:
Remove unnecessary memory barrier before wake_up_* functions.

 net/bluetooth/bnep/core.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index fbf251f..4d6b94d 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c

@@ -484,16 +484,16 @@ static int bnep_session(void *arg)
 	struct net_device *dev = s->dev;
 	struct sock *sk = s->sock->sk;
 	struct sk_buff *skb;
-	wait_queue_t wait;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
 	BT_DBG("");
 
 	set_user_nice(current, -15);
 
-	init_waitqueue_entry(&wait, current);
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		/* Ensure session->terminate is updated */
+		smp_mb__before_atomic();
 
 		if (atomic_read(&s->terminate))
 			break;

@@ -515,9 +515,8 @@ static int bnep_session(void *arg)
 				break;
 		netif_wake_queue(dev);
 
-		schedule();
+		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
-	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(sk_sleep(sk), &wait);
 
 	/* Cleanup session */

@@ -666,7 +665,7 @@ int bnep_del_connection(struct bnep_conndel_req *req)
 	s = __bnep_get_session(req->dst);
 	if (s) {
 		atomic_inc(&s->terminate);
-		wake_up_process(s->task);
+		wake_up_interruptible(sk_sleep(s->sock->sk));
 	} else
 		err = -ENOENT;
 

-- 
2.1.4

It looks like hidp_session_thread has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <redacted>
1/ Fix could not wake up by wake attempts on original wait queues.
2/ Remove unnecessary memory barrier before wake_up_* functions.

---

Changes in v3: None
Changes in v2: None

 net/bluetooth/hidp/core.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 0bec458..076bc50 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c

@@ -36,6 +36,7 @@
 #define VERSION "1.2"
 
 static DECLARE_RWSEM(hidp_session_sem);
+static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq);
 static LIST_HEAD(hidp_session_list);
 
 static unsigned char hidp_keycode[256] = {

@@ -1068,12 +1069,12 @@ static int hidp_session_start_sync(struct hidp_session *session)
  * Wake up session thread and notify it to stop. This is asynchronous and
  * returns immediately. Call this whenever a runtime error occurs and you want
  * the session to stop.
- * Note: wake_up_process() performs any necessary memory-barriers for us.
+ * Note: wake_up_interruptible() performs any necessary memory-barriers for us.
  */
 static void hidp_session_terminate(struct hidp_session *session)
 {
 	atomic_inc(&session->terminate);
-	wake_up_process(session->task);
+	wake_up_interruptible(&hidp_session_wq);
 }
 
 /*

@@ -1180,7 +1181,9 @@ static void hidp_session_run(struct hidp_session *session)
 	struct sock *ctrl_sk = session->ctrl_sock->sk;
 	struct sock *intr_sk = session->intr_sock->sk;
 	struct sk_buff *skb;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+	add_wait_queue(&hidp_session_wq, &wait);
 	for (;;) {
 		/*
 		 * This thread can be woken up two ways:

@@ -1188,12 +1191,10 @@ static void hidp_session_run(struct hidp_session *session)
 		 *    session->terminate flag and wakes this thread up.
 		 *  - Via modifying the socket state of ctrl/intr_sock. This
 		 *    thread is woken up by ->sk_state_changed().
-		 *
-		 * Note: set_current_state() performs any necessary
-		 * memory-barriers for us.
 		 */
-		set_current_state(TASK_INTERRUPTIBLE);
 
+		/* Ensure session->terminate is updated */
+		smp_mb__before_atomic();
 		if (atomic_read(&session->terminate))
 			break;
 

@@ -1227,11 +1228,22 @@ static void hidp_session_run(struct hidp_session *session)
 		hidp_process_transmit(session, &session->ctrl_transmit,
 				      session->ctrl_sock);
 
-		schedule();
+		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
+	remove_wait_queue(&hidp_session_wq, &wait);
 
 	atomic_inc(&session->terminate);
-	set_current_state(TASK_RUNNING);
+
+	/* Ensure session->terminate is updated */
+	smp_mb__after_atomic();
+}
+
+int hidp_session_wake_function(wait_queue_t *wait, unsigned int mode,
+			       int sync, void *key)
+{
+	wake_up_interruptible(&hidp_session_wq);
+
+	return default_wake_function(wait, mode, sync, key);
 }
 
 /*

@@ -1244,7 +1256,8 @@ static void hidp_session_run(struct hidp_session *session)
 static int hidp_session_thread(void *arg)
 {
 	struct hidp_session *session = arg;
-	wait_queue_t ctrl_wait, intr_wait;
+	DEFINE_WAIT_FUNC(ctrl_wait, hidp_session_wake_function);
+	DEFINE_WAIT_FUNC(intr_wait, hidp_session_wake_function);
 
 	BT_DBG("session %p", session);
 

@@ -1254,8 +1267,6 @@ static int hidp_session_thread(void *arg)
 	set_user_nice(current, -15);
 	hidp_set_timer(session);
 
-	init_waitqueue_entry(&ctrl_wait, current);
-	init_waitqueue_entry(&intr_wait, current);
 	add_wait_queue(sk_sleep(session->ctrl_sock->sk), &ctrl_wait);
 	add_wait_queue(sk_sleep(session->intr_sock->sk), &intr_wait);
 	/* This memory barrier is paired with wq_has_sleeper(). See

-- 
2.1.4

It looks like cmtp_session has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <redacted>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Remove unnecessary memory barrier before wake_up_* functions.

---

Changes in v3:
Add brian's Reviewed-by.

Changes in v2: None

 net/bluetooth/cmtp/core.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
index 9e59b66..1152ce3 100644
--- a/net/bluetooth/cmtp/core.c
+++ b/net/bluetooth/cmtp/core.c

@@ -280,16 +280,16 @@ static int cmtp_session(void *arg)
 	struct cmtp_session *session = arg;
 	struct sock *sk = session->sock->sk;
 	struct sk_buff *skb;
-	wait_queue_t wait;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
 	BT_DBG("session %p", session);
 
 	set_user_nice(current, -15);
 
-	init_waitqueue_entry(&wait, current);
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		/* Ensure session->terminate is updated */
+		smp_mb__before_atomic();
 
 		if (atomic_read(&session->terminate))
 			break;

@@ -306,9 +306,8 @@ static int cmtp_session(void *arg)
 
 		cmtp_process_transmit(session);
 
-		schedule();
+		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
-	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(sk_sleep(sk), &wait);
 
 	down_write(&cmtp_session_sem);

@@ -393,7 +392,7 @@ int cmtp_add_connection(struct cmtp_connadd_req *req, struct socket *sock)
 		err = cmtp_attach_device(session);
 		if (err < 0) {
 			atomic_inc(&session->terminate);
-			wake_up_process(session->task);
+			wake_up_interruptible(sk_sleep(session->sock->sk));
 			up_write(&cmtp_session_sem);
 			return err;
 		}

@@ -431,7 +430,11 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
 
 		/* Stop session thread */
 		atomic_inc(&session->terminate);
-		wake_up_process(session->task);
+
+		/* Ensure session->terminate is updated */
+		smp_mb__after_atomic();
+
+		wake_up_interruptible(sk_sleep(session->sock->sk));
 	} else
 		err = -ENOENT;
 

-- 
2.1.4

Hi Jeffy,

On Sun, Feb 12, 2017 at 8:12 PM, Jeffy Chen [off-list ref] wrote:

static?

+{
+       wake_up_interruptible(&hidp_session_wq);
+
+       return default_wake_function(wait, mode, sync, key);

I do not think you need to call default_wake_function() here: the
process is waiting on hidp_session_wq, so the wakeup above is what
will wake up the session. By the time you get to call
default_wake_function() task will already be in wrong state. I think
we should simply return "false" instead of calling
default_wake_function().

Thanks.

-- 
Dmitry

Hi Dmitry,

On 02/14/2017 05:27 AM, Dmitry Torokhov wrote:

Hi Jeffy,

On Sun, Feb 12, 2017 at 8:12 PM, Jeffy Chen [off-list ref] wrote:

quoted

It looks like hidp_session_thread has same pattern as the issue reported in
old rfcomm:

         while (1) {
                 set_current_state(TASK_INTERRUPTIBLE);
                 if (condition)
                         break;
                 // may call might_sleep here
                 schedule();
         }
         __set_current_state(TASK_RUNNING);

Which fixed at:
         dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <redacted>
1/ Fix could not wake up by wake attempts on original wait queues.
2/ Remove unnecessary memory barrier before wake_up_* functions.

---

Changes in v3: None
Changes in v2: None

  net/bluetooth/hidp/core.c | 33 ++++++++++++++++++++++-----------
  1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 0bec458..076bc50 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c

@@ -36,6 +36,7 @@
  #define VERSION "1.2"

  static DECLARE_RWSEM(hidp_session_sem);
+static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq);
  static LIST_HEAD(hidp_session_list);

  static unsigned char hidp_keycode[256] = {

@@ -1068,12 +1069,12 @@ static int hidp_session_start_sync(struct hidp_session *session)
   * Wake up session thread and notify it to stop. This is asynchronous and
   * returns immediately. Call this whenever a runtime error occurs and you want
   * the session to stop.
- * Note: wake_up_process() performs any necessary memory-barriers for us.
+ * Note: wake_up_interruptible() performs any necessary memory-barriers for us.
   */
  static void hidp_session_terminate(struct hidp_session *session)
  {
         atomic_inc(&session->terminate);
-       wake_up_process(session->task);
+       wake_up_interruptible(&hidp_session_wq);
  }

  /*

@@ -1180,7 +1181,9 @@ static void hidp_session_run(struct hidp_session *session)
         struct sock *ctrl_sk = session->ctrl_sock->sk;
         struct sock *intr_sk = session->intr_sock->sk;
         struct sk_buff *skb;
+       DEFINE_WAIT_FUNC(wait, woken_wake_function);

+       add_wait_queue(&hidp_session_wq, &wait);
         for (;;) {
                 /*
                  * This thread can be woken up two ways:

@@ -1188,12 +1191,10 @@ static void hidp_session_run(struct hidp_session *session)
                  *    session->terminate flag and wakes this thread up.
                  *  - Via modifying the socket state of ctrl/intr_sock. This
                  *    thread is woken up by ->sk_state_changed().
-                *
-                * Note: set_current_state() performs any necessary
-                * memory-barriers for us.
                  */
-               set_current_state(TASK_INTERRUPTIBLE);

+               /* Ensure session->terminate is updated */
+               smp_mb__before_atomic();
                 if (atomic_read(&session->terminate))
                         break;

@@ -1227,11 +1228,22 @@ static void hidp_session_run(struct hidp_session *session)
                 hidp_process_transmit(session, &session->ctrl_transmit,
                                       session->ctrl_sock);

-               schedule();
+               wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
         }
+       remove_wait_queue(&hidp_session_wq, &wait);

         atomic_inc(&session->terminate);
-       set_current_state(TASK_RUNNING);
+
+       /* Ensure session->terminate is updated */
+       smp_mb__after_atomic();
+}
+
+int hidp_session_wake_function(wait_queue_t *wait, unsigned int mode,
+                              int sync, void *key)

static?

Oops, sure.

quoted

+{
+       wake_up_interruptible(&hidp_session_wq);
+
+       return default_wake_function(wait, mode, sync, key);

I do not think you need to call default_wake_function() here: the
process is waiting on hidp_session_wq, so the wakeup above is what
will wake up the session. By the time you get to call
default_wake_function() task will already be in wrong state. I think
we should simply return "false" instead of calling
default_wake_function().

Ok, thanx.

quoted

  }

  /*

@@ -1244,7 +1256,8 @@ static void hidp_session_run(struct hidp_session *session)
  static int hidp_session_thread(void *arg)
  {
         struct hidp_session *session = arg;
-       wait_queue_t ctrl_wait, intr_wait;
+       DEFINE_WAIT_FUNC(ctrl_wait, hidp_session_wake_function);
+       DEFINE_WAIT_FUNC(intr_wait, hidp_session_wake_function);

         BT_DBG("session %p", session);

@@ -1254,8 +1267,6 @@ static int hidp_session_thread(void *arg)
         set_user_nice(current, -15);
         hidp_set_timer(session);

-       init_waitqueue_entry(&ctrl_wait, current);
-       init_waitqueue_entry(&intr_wait, current);
         add_wait_queue(sk_sleep(session->ctrl_sock->sk), &ctrl_wait);
         add_wait_queue(sk_sleep(session->intr_sock->sk), &intr_wait);
         /* This memory barrier is paired with wq_has_sleeper(). See
--

2.1.4

Thanks.