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[PATCH] i40iw: Add a value assignment to avoid sleep-in-atomic bug caused by uninitialized value

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  [PATCH] i40iw: Add a value assignment to avoid sleep-in-atomic bug caused by uninitialized value Jia-Ju Bai <baijiaju1990@163.com> - 2017-06-01 04:10 +0200
    Re: [PATCH] i40iw: Add a value assignment to avoid sleep-in-atomic  bug caused by uninitialized value Shiraz Saleem <shiraz.saleem@intel.com> - 2017-06-02 23:20 +0200

#1654756 — [PATCH] i40iw: Add a value assignment to avoid sleep-in-atomic bug caused by uninitialized value

The value "cqp_request->waiting" indicates whether the sleeping operation 
should be performed, and it is not assigned in i40iw_get_cqp_request, so 
the driver may sleep in interrupt handling. The function call path is:

i40iw_dpc (tasklet_init indicates it handles interrupt)
  i40iw_process_aeq
    i40iw_next_iw_state
      i40iw_hw_modify_qp (call i40iw_get_cqp_request)
        i40iw_handle_cqp_op
          i40iw_wait_event --> may sleep

To fix it, "cqp_request->waiting" is assigned in "else" branch in
i40iw_get_cqp_request.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
---
 drivers/infiniband/hw/i40iw/i40iw_utils.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/hw/i40iw/i40iw_utils.c b/drivers/infiniband/hw/i40iw/i40iw_utils.c
index 409a378..0f4e633 100644
--- a/drivers/infiniband/hw/i40iw/i40iw_utils.c
+++ b/drivers/infiniband/hw/i40iw/i40iw_utils.c
@@ -326,6 +326,7 @@ struct i40iw_cqp_request *i40iw_get_cqp_request(struct i40iw_cqp *cqp, bool wait
 		cqp_request->waiting = true;
 	} else {
 		atomic_set(&cqp_request->refcount, 1);
+		cqp_request->waiting = false;
 	}
 	return cqp_request;
 }
-- 
1.7.9.5

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#1656563 — Re: [PATCH] i40iw: Add a value assignment to avoid sleep-in-atomic bug caused by uninitialized value

On Thu, Jun 01, 2017 at 10:11:16AM +0800, Jia-Ju Bai wrote:
> The value "cqp_request->waiting" indicates whether the sleeping operation 
> should be performed, and it is not assigned in i40iw_get_cqp_request, so 
> the driver may sleep in interrupt handling. The function call path is:
> 
> i40iw_dpc (tasklet_init indicates it handles interrupt)
>   i40iw_process_aeq
>     i40iw_next_iw_state
>       i40iw_hw_modify_qp (call i40iw_get_cqp_request)
>         i40iw_handle_cqp_op
>           i40iw_wait_event --> may sleep
> 
> To fix it, "cqp_request->waiting" is assigned in "else" branch in
> i40iw_get_cqp_request.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
> ---
>  drivers/infiniband/hw/i40iw/i40iw_utils.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/infiniband/hw/i40iw/i40iw_utils.c b/drivers/infiniband/hw/i40iw/i40iw_utils.c
> index 409a378..0f4e633 100644
> --- a/drivers/infiniband/hw/i40iw/i40iw_utils.c
> +++ b/drivers/infiniband/hw/i40iw/i40iw_utils.c
> @@ -326,6 +326,7 @@ struct i40iw_cqp_request *i40iw_get_cqp_request(struct i40iw_cqp *cqp, bool wait
>  		cqp_request->waiting = true;
>  	} else {
>  		atomic_set(&cqp_request->refcount, 1);
> +		cqp_request->waiting = false;
>  	}
>  	return cqp_request;
>  }
> --

Hi Jia - cqp_request->waiting is always initialized. If cqp_request object is 
allocated using kzalloc, it is initialized to 0. For those cqp_request object that are
retrieved from the cqp list 'cqp->cqp_avail_reqs', the waiting flag is set to false
when it is put back on the list via i40iw_free_cqp_request. So there should be no issue
here.

Shiraz

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