[PATCH] cw1200: Fix a sleep-in-atomic bug in cw1200_tx_confirm_cb and cw1200_cqm_bssloss_sm

[PATCH] cw1200: Fix a sleep-in-atomic bug in cw1200_tx_confirm_cb and cw1200_cqm_bssloss_sm

[Jia-Ju Bai]

The driver may sleep under a spin lock, and the function call path is:
cw1200_tx_confirm_cb (acquire the lock by spin_lock)
  __cw1200_cqm_bssloss_sm
    cancel_work_sync --> may sleep

cw1200_cqm_bssloss_sm
  __cw1200_cqm_bssloss_sm
    cancel_work_sync --> may sleep

To fix it, the lock is released before cancel_work_sync, and the lock 
is acquired again after this function.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
---
 drivers/net/wireless/st/cw1200/sta.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/wireless/st/cw1200/sta.c b/drivers/net/wireless/st/cw1200/sta.c
index a522248..d5f7698 100644
--- a/drivers/net/wireless/st/cw1200/sta.c
+++ b/drivers/net/wireless/st/cw1200/sta.c
@@ -154,7 +154,9 @@ void __cw1200_cqm_bssloss_sm(struct cw1200_common *priv,
 	int tx = 0;
 
 	priv->delayed_link_loss = 0;
+	spin_unlock(&priv->bss_loss_lock);
 	cancel_work_sync(&priv->bss_params_work);
+	spin_lock(&priv->bss_loss_lock);
 
 	pr_debug("[STA] CQM BSSLOSS_SM: state: %d init %d good %d bad: %d txlock: %d uj: %d\n",
 		 priv->bss_loss_state,
-- 
1.7.9.5

Re: cw1200: Fix a sleep-in-atomic bug in cw1200_tx_confirm_cb and cw1200_cqm_bssloss_sm

[Kalle Valo]

Jia-Ju Bai <baijiaju1990@163.com> wrote:

> The driver may sleep under a spin lock, and the function call path is:
> cw1200_tx_confirm_cb (acquire the lock by spin_lock)
>   __cw1200_cqm_bssloss_sm
>     cancel_work_sync --> may sleep
> 
> cw1200_cqm_bssloss_sm
>   __cw1200_cqm_bssloss_sm
>     cancel_work_sync --> may sleep
> 
> To fix it, the lock is released before cancel_work_sync, and the lock 
> is acquired again after this function.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>

I assume that you haven't tested this on a real device and only compile tested.
You should mention that in the commit log.

Releasing a lock held by calling function is evil. Did you do any lock analysis
or are you just blindly releasing locks to fix a warning in your tool?

Also I would like to have an ack from a reviewer before I can take patches like
this.

Patch set to Changes Requested.

-- 
https://patchwork.kernel.org/patch/9758613/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches