On Tue, Oct 24, 2017 at 2:40 AM, Bryan O'Donoghue pure.logic@nexus-software.ie wrote:

On 24/10/17 10:35, Bryan O'Donoghue wrote:

...

On 24/10/17 09:25, Kees Cook wrote:

...

In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly.

Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: "Bryan O'Donoghue" pure.logic@nexus-software.ie Cc: Johan Hovold johan@kernel.org Cc: Alex Elder elder@kernel.org Cc: greybus-dev@lists.linaro.org Cc: devel@driverdev.osuosl.org Signed-off-by: Kees Cook keescook@chromium.org

---

drivers/staging/greybus/loopback.c | 14 ++++---------- drivers/staging/greybus/operation.c | 7 +++---- 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c index 08e255884206..045aaf81113a 100644 --- a/drivers/staging/greybus/loopback.c +++ b/drivers/staging/greybus/loopback.c @@ -572,16 +572,11 @@ static void gb_loopback_async_operation_work(struct work_struct *work) gb_loopback_async_operation_put(op_async); } -static void gb_loopback_async_operation_timeout(unsigned long data) +static void gb_loopback_async_operation_timeout(struct timer_list *t) {

• struct gb_loopback_async_operation *op_async;
• u16 id = data;

• struct gb_loopback_async_operation *op_async =

•    from_timer(op_async, t, timer);
  

• op_async = gb_loopback_operation_find(id);
• if (!op_async) {

•    pr_err("operation %d not found - time out ?\n", id);
  

•    return;
  

• }

Hi Kees, you need to add

 gb_loopback_async_operation_get(op_async); when dropping the

gb_loopback_operation_find() call here.

Actually:

    spin_lock_irqsave(&gb_dev.lock, flags);
    gb_loopback_async_operation_get(op_async);
    spin_unlock_irqrestore(&gb_dev.lock, flags);

Shouldn't the get/put follow the lifetime of the timer running instead? It shouldnt' be possible to free the op_async while the timer is still pending/running.

-Kees

On Tue, Oct 24, 2017 at 5:52 AM, Bryan O'Donoghue pure.logic@nexus-software.ie wrote:

On 24/10/17 13:47, Kees Cook wrote:

...

On Tue, Oct 24, 2017 at 2:40 AM, Bryan O'Donoghue pure.logic@nexus-software.ie wrote:

...

On 24/10/17 10:35, Bryan O'Donoghue wrote:

...

On 24/10/17 09:25, Kees Cook wrote:

...

In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly.

Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: "Bryan O'Donoghue" pure.logic@nexus-software.ie Cc: Johan Hovold johan@kernel.org Cc: Alex Elder elder@kernel.org Cc: greybus-dev@lists.linaro.org Cc: devel@driverdev.osuosl.org Signed-off-by: Kees Cook keescook@chromium.org

---

drivers/staging/greybus/loopback.c | 14 ++++---------- drivers/staging/greybus/operation.c | 7 +++---- 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c index 08e255884206..045aaf81113a 100644 --- a/drivers/staging/greybus/loopback.c +++ b/drivers/staging/greybus/loopback.c @@ -572,16 +572,11 @@ static void gb_loopback_async_operation_work(struct work_struct *work) gb_loopback_async_operation_put(op_async); } -static void gb_loopback_async_operation_timeout(unsigned long data) +static void gb_loopback_async_operation_timeout(struct timer_list *t) {

• struct gb_loopback_async_operation *op_async;
• u16 id = data;

• struct gb_loopback_async_operation *op_async =

•    from_timer(op_async, t, timer);
  

• op_async = gb_loopback_operation_find(id);
• if (!op_async) {

•    pr_err("operation %d not found - time out ?\n", id);
  

•    return;
  

• }

Hi Kees, you need to add

  gb_loopback_async_operation_get(op_async); when dropping the

gb_loopback_operation_find() call here.

Actually:

     spin_lock_irqsave(&gb_dev.lock, flags);
     gb_loopback_async_operation_get(op_async);
     spin_unlock_irqrestore(&gb_dev.lock, flags);

Shouldn't the get/put follow the lifetime of the timer running instead? It shouldnt' be possible to free the op_async while the timer is still pending/running.

The timeout timer runs for an operation that never completed but on the regular "everything is good" path you end up doing del_timer_sync(&op_async->timer); so the timer doesn't run.

As far as I can tell, the get/put is already happening external to the timer:

gb_loopback_async_operation(): ... op_async = kzalloc(sizeof(*op_async), GFP_KERNEL); ... INIT_WORK(&op_async->work, gb_loopback_async_operation_work); kref_init(&op_async->kref); ... op_async->pending = true; ... ret = gb_operation_request_send(operation, gb_loopback_async_operation_callback, 0, GFP_KERNEL); ... timer_setup(&op_async->timer, gb_loopback_async_operation_timeout, 0); op_async->timer.expires = jiffies + gb->jiffy_timeout; add_timer(&op_async->timer);

gb_loopback_async_operation_callback(): (run by operation) ... op_async->pending = false; del_timer_sync(&op_async->timer); gb_loopback_async_operation_put(op_async);

gb_loopback_async_operation_work(): (scheduled by timer) ... op_async->pending = false; gb_loopback_async_operation_put(op_async);

(Doing a get/put in the timer callback itself shouldn't be happening: it must already be pinned in memory for the callback to run.)

-Kees

On Tue, Oct 24, 2017 at 6:30 AM, Bryan O'Donoghue pure.logic@nexus-software.ie wrote:

On 24/10/17 14:14, Kees Cook wrote:

...

On Tue, Oct 24, 2017 at 5:52 AM, Bryan O'Donoghue pure.logic@nexus-software.ie wrote:

...

On 24/10/17 13:47, Kees Cook wrote:

...

On Tue, Oct 24, 2017 at 2:40 AM, Bryan O'Donoghue pure.logic@nexus-software.ie wrote:

...

On 24/10/17 10:35, Bryan O'Donoghue wrote:

...

On 24/10/17 09:25, Kees Cook wrote: > > > > In preparation for unconditionally passing the struct timer_list > pointer > to > all timer callbacks, switch to using the new timer_setup() and > from_timer() > to pass the timer pointer explicitly. > > Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org > Cc: "Bryan O'Donoghue" pure.logic@nexus-software.ie > Cc: Johan Hovold johan@kernel.org > Cc: Alex Elder elder@kernel.org > Cc: greybus-dev@lists.linaro.org > Cc: devel@driverdev.osuosl.org > Signed-off-by: Kees Cook keescook@chromium.org > --- > drivers/staging/greybus/loopback.c | 14 ++++---------- > drivers/staging/greybus/operation.c | 7 +++---- > 2 files changed, 7 insertions(+), 14 deletions(-) > > diff --git a/drivers/staging/greybus/loopback.c > b/drivers/staging/greybus/loopback.c > index 08e255884206..045aaf81113a 100644 > --- a/drivers/staging/greybus/loopback.c > +++ b/drivers/staging/greybus/loopback.c > @@ -572,16 +572,11 @@ static void > gb_loopback_async_operation_work(struct > work_struct *work) > gb_loopback_async_operation_put(op_async); > } > -static void gb_loopback_async_operation_timeout(unsigned long data) > +static void gb_loopback_async_operation_timeout(struct timer_list > *t) > { > - struct gb_loopback_async_operation *op_async; > - u16 id = data; > + struct gb_loopback_async_operation *op_async = > + from_timer(op_async, t, timer); > - op_async = gb_loopback_operation_find(id); > - if (!op_async) { > - pr_err("operation %d not found - time out ?\n", id); > - return; > - }

Hi Kees, you need to add

   gb_loopback_async_operation_get(op_async); when dropping the

gb_loopback_operation_find() call here.

Actually:

      spin_lock_irqsave(&gb_dev.lock, flags);
      gb_loopback_async_operation_get(op_async);
      spin_unlock_irqrestore(&gb_dev.lock, flags);

Shouldn't the get/put follow the lifetime of the timer running instead? It shouldnt' be possible to free the op_async while the timer is still pending/running.

The timeout timer runs for an operation that never completed but on the regular "everything is good" path you end up doing del_timer_sync(&op_async->timer); so the timer doesn't run.

As far as I can tell, the get/put is already happening external to the timer:

gb_loopback_async_operation(): ... op_async = kzalloc(sizeof(*op_async), GFP_KERNEL); ... INIT_WORK(&op_async->work, gb_loopback_async_operation_work); kref_init(&op_async->kref); ... op_async->pending = true; ... ret = gb_operation_request_send(operation,

gb_loopback_async_operation_callback, 0, GFP_KERNEL); ... timer_setup(&op_async->timer, gb_loopback_async_operation_timeout, 0); op_async->timer.expires = jiffies + gb->jiffy_timeout; add_timer(&op_async->timer);

gb_loopback_async_operation_callback(): (run by operation) ... op_async->pending = false; del_timer_sync(&op_async->timer); gb_loopback_async_operation_put(op_async);

gb_loopback_async_operation_work(): (scheduled by timer) ... op_async->pending = false; gb_loopback_async_operation_put(op_async);

...

(Doing a get/put in the timer callback itself shouldn't be happening: it must already be pinned in memory for the callback to run.)

Both gb_loopback_async_operation_callback() and (gb_loopback_async_operation_timeout || gb_loopback_async_operation_work()) can run in parallel so the get in the timer callback means we can let the timer stuff free-run w/r to gb_loopback_async_operation_callback() - take a reference indicating we still want that object and then let gb_loopback_async_operation_work() run.

Ah right, we're protecting the scheduled worker thread. I'll send a v2, thanks!

-Kees