[PATCH net-next] net: wwan: mhi_wwan_ctrl: Fix possible deadlock

Lockdep detected possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&mhiwwan->rx_lock);
                               local_irq_disable();
                               lock(&mhi_cntrl->pm_lock);
                               lock(&mhiwwan->rx_lock);
   <Interrupt>
     lock(&mhi_cntrl->pm_lock);

  *** DEADLOCK ***

To prevent this we need to disable the soft-interrupts when taking
the rx_lock.

Cc: stable@vger.kernel.org
Fixes: fa588eba632d ("net: Add Qcom WWAN control driver")
Reported-by: Thomas Perrot <redacted>
Signed-off-by: Loic Poulain <redacted>
---
 drivers/net/wwan/mhi_wwan_ctrl.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index 1e18420..d0a98f3 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c

@@ -41,14 +41,14 @@ struct mhi_wwan_dev {
 /* Increment RX budget and schedule RX refill if necessary */
 static void mhi_wwan_rx_budget_inc(struct mhi_wwan_dev *mhiwwan)
 {
-	spin_lock(&mhiwwan->rx_lock);
+	spin_lock_bh(&mhiwwan->rx_lock);
 
 	mhiwwan->rx_budget++;
 
 	if (test_bit(MHI_WWAN_RX_REFILL, &mhiwwan->flags))
 		schedule_work(&mhiwwan->rx_refill);
 
-	spin_unlock(&mhiwwan->rx_lock);
+	spin_unlock_bh(&mhiwwan->rx_lock);
 }
 
 /* Decrement RX budget if non-zero and return true on success */

@@ -56,7 +56,7 @@ static bool mhi_wwan_rx_budget_dec(struct mhi_wwan_dev *mhiwwan)
 {
 	bool ret = false;
 
-	spin_lock(&mhiwwan->rx_lock);
+	spin_lock_bh(&mhiwwan->rx_lock);
 
 	if (mhiwwan->rx_budget) {
 		mhiwwan->rx_budget--;

@@ -64,7 +64,7 @@ static bool mhi_wwan_rx_budget_dec(struct mhi_wwan_dev *mhiwwan)
 			ret = true;
 	}
 
-	spin_unlock(&mhiwwan->rx_lock);
+	spin_unlock_bh(&mhiwwan->rx_lock);
 
 	return ret;
 }

@@ -130,9 +130,9 @@ static void mhi_wwan_ctrl_stop(struct wwan_port *port)
 {
 	struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);
 
-	spin_lock(&mhiwwan->rx_lock);
+	spin_lock_bh(&mhiwwan->rx_lock);
 	clear_bit(MHI_WWAN_RX_REFILL, &mhiwwan->flags);
-	spin_unlock(&mhiwwan->rx_lock);
+	spin_unlock_bh(&mhiwwan->rx_lock);
 
 	cancel_work_sync(&mhiwwan->rx_refill);
 

-- 
2.7.4

On Fri, Aug 6, 2021 at 1:24 PM Loic Poulain [off-list ref] wrote:

Lockdep detected possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&mhiwwan->rx_lock);
                               local_irq_disable();
                               lock(&mhi_cntrl->pm_lock);
                               lock(&mhiwwan->rx_lock);
   <Interrupt>
     lock(&mhi_cntrl->pm_lock);

  *** DEADLOCK ***

To prevent this we need to disable the soft-interrupts when taking
the rx_lock.

Cc: stable@vger.kernel.org
Fixes: fa588eba632d ("net: Add Qcom WWAN control driver")
Reported-by: Thomas Perrot <redacted>
Signed-off-by: Loic Poulain <redacted>

Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>

On Fri,  6 Aug 2021 12:35:09 +0200 Loic Poulain wrote:

Lockdep detected possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&mhiwwan->rx_lock);
                               local_irq_disable();
                               lock(&mhi_cntrl->pm_lock);
                               lock(&mhiwwan->rx_lock);
   <Interrupt>
     lock(&mhi_cntrl->pm_lock);

  *** DEADLOCK ***

To prevent this we need to disable the soft-interrupts when taking
the rx_lock.

Cc: stable@vger.kernel.org
Fixes: fa588eba632d ("net: Add Qcom WWAN control driver")
Reported-by: Thomas Perrot <redacted>
Signed-off-by: Loic Poulain <redacted>

This is for net, right? Despite it's subject annotation?

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Fri,  6 Aug 2021 12:35:09 +0200 you wrote:

Lockdep detected possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&mhiwwan->rx_lock);
                               local_irq_disable();
                               lock(&mhi_cntrl->pm_lock);
                               lock(&mhiwwan->rx_lock);
   <Interrupt>
     lock(&mhi_cntrl->pm_lock);

[...]

Here is the summary with links:
  - [net-next] net: wwan: mhi_wwan_ctrl: Fix possible deadlock
    https://git.kernel.org/netdev/net/c/34737e1320db

You are awesome, thank you!
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