[PATCH 5.15.y] phy: qcom: qmp: Fix NULL pointer dereference for USB Uni PHYs

[Krishna Kurapati]

Commit [1] introduced DP support to QMP driver. While doing so, the
dp and usb configuration structures were added to a combo_phy_cfg
structure. During probe, the match data is used to parse and identify the
dp and usb configs separately. While doing so, the usb_cfg variable
represents the configuration parameters for USB part of the phy (whether
it is DP-Cobo or Uni). during probe, one corner case of parsing usb_cfg
for Uni PHYs is left incomplete and it is left as NULL. This NULL variable
further percolates down to qmp_phy_create() call essentially getting
de-referenced and causing a crash.

Subsequently, commit [2] split the driver into multiple files, each
handling a specific PHY type (USB, DP-Combo, UFS, PCIe). During this
refactoring, the probing process was modified, and the NULL pointer
dereference issue no longer showed up.

[1]: https://lore.kernel.org/all/20200916231202.3637932-8-swboyd@chromium.org/
[2]: https://lore.kernel.org/all/20220607213203.2819885-1-dmitry.baryshkov@linaro.org/

Fixes: 52e013d0bffa ("phy: qcom-qmp: Add support for DP in USB3+DP combo phy")
Cc: stable at vger.kernel.org # 5.15.y
Signed-off-by: Krishna Kurapati <quic_kriskura at quicinc.com>
---
 drivers/phy/qualcomm/phy-qcom-qmp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
index eef863108bfe..e22ee71aa060 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
@@ -5714,6 +5714,8 @@ static int qcom_qmp_phy_probe(struct platform_device *pdev)
 
 		usb_cfg = combo_cfg->usb_cfg;
 		cfg = usb_cfg; /* Setup clks and regulators */
+	} else {
+		usb_cfg = cfg;
 	}
 
 	/* per PHY serdes; usually located at base address */
-- 
2.34.1