linux-kernel - [PATCH v3] bus: mhi: core: Check state before processing power

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Message-Id: <1615409365-8165-1-git-send-email-jhugo@codeaurora.org>
Date:   Wed, 10 Mar 2021 13:49:25 -0700
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     manivannan.sadhasivam@...aro.org, hemantk@...eaurora.org
Cc:     bbhatt@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jeffrey Hugo <jhugo@...eaurora.org>
Subject: [PATCH v3] bus: mhi: core: Check state before processing power_down

We cannot process a power_down if the power state is DISABLED.  There is
no valid mhi_ctxt in that case, so attepting to process the power_down
will likely result in a null pointer dereference.  If the power state is
DISABLED, there is nothing to do anyways, so just bail early.

Signed-off-by: Jeffrey Hugo <jhugo@...eaurora.org>
---

v3: Move the pm_lock use up
v2: Fix subject and tweak the locking to avoid needless lock/unlock/relock

 drivers/bus/mhi/core/pm.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index 414da4f..ea62549 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -1149,6 +1149,7 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
 		mhi_deinit_dev_ctxt(mhi_cntrl);
 
 error_dev_ctxt:
+	mhi_cntrl->pm_state = MHI_PM_DISABLE;
 	mutex_unlock(&mhi_cntrl->pm_mutex);
 
 	return ret;
@@ -1160,12 +1161,19 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
 	enum mhi_pm_state cur_state, transition_state;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
 
+	mutex_lock(&mhi_cntrl->pm_mutex);
+	write_lock_irq(&mhi_cntrl->pm_lock);
+	cur_state = mhi_cntrl->pm_state;
+	if (cur_state == MHI_PM_DISABLE) {
+		write_unlock_irq(&mhi_cntrl->pm_lock);
+		mutex_unlock(&mhi_cntrl->pm_mutex);
+		return; /* Already powered down */
+	}
+
 	/* If it's not a graceful shutdown, force MHI to linkdown state */
 	transition_state = (graceful) ? MHI_PM_SHUTDOWN_PROCESS :
 			   MHI_PM_LD_ERR_FATAL_DETECT;
 
-	mutex_lock(&mhi_cntrl->pm_mutex);
-	write_lock_irq(&mhi_cntrl->pm_lock);
 	cur_state = mhi_tryset_pm_state(mhi_cntrl, transition_state);
 	if (cur_state != transition_state) {
 		dev_err(dev, "Failed to move to state: %s from: %s\n",
-- 
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