[PATCH v2] PCI: imx6: Avoid dereferencing a NULL clock name

[Rudi Heitbaum]

of_clk_bulk_get() leaves clk_bulk_data::id as NULL for every clock that
has no matching entry in "clock-names", which is legal: a node may list
more "clocks" phandles than it names. Both scans of the bulk array
dereference that id unconditionally, so such a node oopses during probe.

The loop in imx_pcie_probe() has been wrong since it was written. The
loop in imx_setup_phy_mpll() was not: it read a fixed clks[] whose ids
came from the driver's own clk_names[] and were never NULL, and only
became wrong when the driver moved to the bulk array.

Check clk_bulk_data::id before dereferencing it in both.

Fixes: f6a1fdfc78e2 ("PCI: imx6: Use devm_clk_bulk_get_all() to fetch clocks")
Fixes: d8574ce57d76 ("PCI: imx6: Add external reference clock input mode support")
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Richard Zhu <hongxing.zhu@xxxxxxx>
Signed-off-by: Rudi Heitbaum <rudi@xxxxxxxxxxxx>
---
Changes in v2:
- Also guard the identical unchecked dereference in imx_setup_phy_mpll(),
  reported by Sashiko and requested by Manivannan Sadhasivam.
- Add the Fixes: tag for that site.
- v1: https://lore.kernel.org/all/am8iBwJSEhYhWTqk@6cfee64030a6/

 drivers/pci/controller/dwc/pci-imx6.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 39790e66b98d..f8dd83a88ddf 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -542,7 +542,7 @@ static int imx_setup_phy_mpll(struct imx_pcie *imx_pcie)
 		return 0;
 
 	for (i = 0; i < imx_pcie->num_clks; i++)
-		if (strncmp(clks[i].id, "pcie_phy", 8) == 0)
+		if (clks[i].id && strncmp(clks[i].id, "pcie_phy", 8) == 0)
 			phy_rate = clk_get_rate(clks[i].clk);
 
 	switch (phy_rate) {
@@ -1836,7 +1836,8 @@ static int imx_pcie_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, imx_pcie->num_clks,
 				     "failed to get clocks\n");
 	for (i = 0; i < imx_pcie->num_clks; i++)
-		if (strncmp(imx_pcie->clks[i].id, "extref", 6) == 0)
+		if (imx_pcie->clks[i].id &&
+		    strncmp(imx_pcie->clks[i].id, "extref", 6) == 0)
 			imx_pcie->enable_ext_refclk = true;
 
 	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_PHYDRV)) {
-- 
2.53.0