[PATCH v5 3/5] phy: qcom: qmp-usb-legacy: Fix possible NULL-deref on early runtime suspend

[Loic Poulain <loic.poulain@oss.qualcomm.com>]

There is a small window where the runtime suspend callback may run
after pm_runtime_enable() and before pm_runtime_forbid(). In this
case, a crash occurs because runtime suspend/resume dereferences
qmp->phy pointer, which is not yet initialized:
        `if (!qmp->phy->init_count) {`

This can also happen if user re-enables runtime-pm via the sysfs
attribute before qmp phy is initialized.

Similarly to other qcom phy drivers, introduce a qmp->phy_initialized
variable that can be used to avoid relying on the possibly uninitialized
phy pointer.

Fixes: e464a3180a43 ("phy: qcom-qmp-usb: split off the legacy USB+dp_com support")
Reviewed-by: Abel Vesa <abel.vesa@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 drivers/phy/qualcomm/phy-qcom-qmp-usb-legacy.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-usb-legacy.c b/drivers/phy/qualcomm/phy-qcom-qmp-usb-legacy.c
index 8bf951b0490cfd811635df8940de1b789e21b46c..fc490589c8e4888770807a60170905a1c7610421 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-usb-legacy.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-usb-legacy.c
@@ -542,6 +542,8 @@ struct qmp_usb {
 
 	enum phy_mode mode;
 
+	bool phy_initialized;
+
 	struct phy *phy;
 
 	struct clk_fixed_rate pipe_clk_fixed;
@@ -895,6 +897,7 @@ static int qmp_usb_legacy_power_off(struct phy *phy)
 
 static int qmp_usb_legacy_enable(struct phy *phy)
 {
+	struct qmp_usb *qmp = phy_get_drvdata(phy);
 	int ret;
 
 	ret = qmp_usb_legacy_init(phy);
@@ -904,14 +907,19 @@ static int qmp_usb_legacy_enable(struct phy *phy)
 	ret = qmp_usb_legacy_power_on(phy);
 	if (ret)
 		qmp_usb_legacy_exit(phy);
+	else
+		qmp->phy_initialized = true;
 
 	return ret;
 }
 
 static int qmp_usb_legacy_disable(struct phy *phy)
 {
+	struct qmp_usb *qmp = phy_get_drvdata(phy);
 	int ret;
 
+	qmp->phy_initialized = false;
+
 	ret = qmp_usb_legacy_power_off(phy);
 	if (ret)
 		return ret;
@@ -988,7 +996,7 @@ static int __maybe_unused qmp_usb_legacy_runtime_suspend(struct device *dev)
 
 	dev_vdbg(dev, "Suspending QMP phy, mode:%d\n", qmp->mode);
 
-	if (!qmp->phy->init_count) {
+	if (!qmp->phy_initialized) {
 		dev_vdbg(dev, "PHY not initialized, bailing out\n");
 		return 0;
 	}
@@ -1009,7 +1017,7 @@ static int __maybe_unused qmp_usb_legacy_runtime_resume(struct device *dev)
 
 	dev_vdbg(dev, "Resuming QMP phy, mode:%d\n", qmp->mode);
 
-	if (!qmp->phy->init_count) {
+	if (!qmp->phy_initialized) {
 		dev_vdbg(dev, "PHY not initialized, bailing out\n");
 		return 0;
 	}

-- 
2.34.1