linux-kernel - [PATCH] usb: ehci-fsl: Fix use of private data to avoid -Wflex-array-member-not-at-end warning

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Message-ID: <8139e4cc-4e5c-40e2-9c4b-717ad3215868@rowland.harvard.edu>
Date: Thu, 27 Mar 2025 15:31:15 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] usb: ehci-fsl: Fix use of private data to avoid
 -Wflex-array-member-not-at-end warning

In the course of fixing up the usages of flexible arrays, Gustavo
submitted a patch updating the ehci-fsl driver.  However, the patch
was wrong because the driver was using the .priv member of the
ehci_hcd structure incorrectly.  The private data is not supposed to
be a wrapper containing the ehci_hcd structure; it is supposed to be a
sub-structure stored in the .priv member.

Fix the problem by replacing the ehci_fsl structure with
ehci_fsl_priv, containing only the private data, along with a suitable
conversion macro for accessing it.  This removes the problem of having
data follow a flexible array member.

Reported-by: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Link: https://lore.kernel.org/linux-usb/Z-R9BcnSzrRv5FX_@kspp/

---

 drivers/usb/host/ehci-fsl.c |   25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

Index: usb-devel/drivers/usb/host/ehci-fsl.c
===================================================================
--- usb-devel.orig/drivers/usb/host/ehci-fsl.c
+++ usb-devel/drivers/usb/host/ehci-fsl.c
@@ -410,15 +410,13 @@ static int ehci_fsl_setup(struct usb_hcd
 	return retval;
 }
 
-struct ehci_fsl {
-	struct ehci_hcd	ehci;
-
-#ifdef CONFIG_PM
+struct ehci_fsl_priv {
 	/* Saved USB PHY settings, need to restore after deep sleep. */
 	u32 usb_ctrl;
-#endif
 };
 
+#define hcd_to_ehci_fsl_priv(h) ((struct ehci_fsl_priv *) hcd_to_ehci(h)->priv)
+
 #ifdef CONFIG_PM
 
 #ifdef CONFIG_PPC_MPC512x
@@ -566,17 +564,10 @@ static inline int ehci_fsl_mpc512x_drv_r
 }
 #endif /* CONFIG_PPC_MPC512x */
 
-static struct ehci_fsl *hcd_to_ehci_fsl(struct usb_hcd *hcd)
-{
-	struct ehci_hcd *ehci = hcd_to_ehci(hcd);
-
-	return container_of(ehci, struct ehci_fsl, ehci);
-}
-
 static int ehci_fsl_drv_suspend(struct device *dev)
 {
 	struct usb_hcd *hcd = dev_get_drvdata(dev);
-	struct ehci_fsl *ehci_fsl = hcd_to_ehci_fsl(hcd);
+	struct ehci_fsl_priv *priv = hcd_to_ehci_fsl_priv(hcd);
 	void __iomem *non_ehci = hcd->regs;
 
 	if (of_device_is_compatible(dev->parent->of_node,
@@ -589,14 +580,14 @@ static int ehci_fsl_drv_suspend(struct d
 	if (!fsl_deep_sleep())
 		return 0;
 
-	ehci_fsl->usb_ctrl = ioread32be(non_ehci + FSL_SOC_USB_CTRL);
+	priv->usb_ctrl = ioread32be(non_ehci + FSL_SOC_USB_CTRL);
 	return 0;
 }
 
 static int ehci_fsl_drv_resume(struct device *dev)
 {
 	struct usb_hcd *hcd = dev_get_drvdata(dev);
-	struct ehci_fsl *ehci_fsl = hcd_to_ehci_fsl(hcd);
+	struct ehci_fsl_priv *priv = hcd_to_ehci_fsl_priv(hcd);
 	struct ehci_hcd *ehci = hcd_to_ehci(hcd);
 	void __iomem *non_ehci = hcd->regs;
 
@@ -612,7 +603,7 @@ static int ehci_fsl_drv_resume(struct de
 	usb_root_hub_lost_power(hcd->self.root_hub);
 
 	/* Restore USB PHY settings and enable the controller. */
-	iowrite32be(ehci_fsl->usb_ctrl, non_ehci + FSL_SOC_USB_CTRL);
+	iowrite32be(priv->usb_ctrl, non_ehci + FSL_SOC_USB_CTRL);
 
 	ehci_reset(ehci);
 	ehci_fsl_reinit(ehci);
@@ -671,7 +662,7 @@ static int ehci_start_port_reset(struct
 #endif /* CONFIG_USB_OTG */
 
 static const struct ehci_driver_overrides ehci_fsl_overrides __initconst = {
-	.extra_priv_size = sizeof(struct ehci_fsl),
+	.extra_priv_size = sizeof(struct ehci_fsl_priv),
 	.reset = ehci_fsl_setup,
 };