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SubjectRe: [PATCH] usb: xhci-pci: reorder removal to avoid use-after-free
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Hi,

On 14-08-19 13:39, Schmid, Carsten wrote:
> On driver removal, the platform_device_unregister call
> attached through devm_add_action_or_reset was executed
> after usb_hcd_pci_remove.
> This lead to a use-after-free for the iomem resorce of
> the xhci-ext-caps driver in the platform removal
> because the parent of the resource was freed earlier.
>
> Fix this by reordering of the removal sequence.
>
> Signed-off-by: Carsten Schmid <carsten_schmid@mentor.com>

Assuming this has been tested, overal this looks good to me.

But there are 2 things to fix:

1) Maybe pick a more descriptive struct member name then pdev.
pdev with pci-devices often points to a pci_device ...
How about: role_switch_pdev ?

2) xhci_ext_cap_init() is not the last call which can fail in
xhci_pci_probe(), since you now no longer use devm_add_action_or_reset
for auto-cleanup, you must now manually cleanup by calling
xhci_ext_cap_remove() when later steps of xhci_pci_probe() fail.
it looks like you will need a new ext_cap_remove error-exit label
for this put above the put_usb3_hcd label and goto this new label
instead of to put_usb3_hcd in all error paths after a successful call
to xhci_ext_cap_init()

Regards,

Hans


> ---
> drivers/usb/host/xhci-ext-caps.c | 22 ++++++++++++----------
> drivers/usb/host/xhci-pci.c | 4 ++++
> drivers/usb/host/xhci-pci.h | 19 +++++++++++++++++++
> drivers/usb/host/xhci.h | 1 +
> 4 files changed, 36 insertions(+), 10 deletions(-)
> create mode 100644 drivers/usb/host/xhci-pci.h
>
> diff --git a/drivers/usb/host/xhci-ext-caps.c b/drivers/usb/host/xhci-ext-caps.c
> index 399113f9fc5c..d2ab1e2a39c0 100644
> --- a/drivers/usb/host/xhci-ext-caps.c
> +++ b/drivers/usb/host/xhci-ext-caps.c
> @@ -7,21 +7,19 @@
>
> #include <linux/platform_device.h>
> #include "xhci.h"
> +#include "xhci-pci.h"
>
> #define USB_SW_DRV_NAME "intel_xhci_usb_sw"
> #define USB_SW_RESOURCE_SIZE 0x400
>
> -static void xhci_intel_unregister_pdev(void *arg)
> -{
> - platform_device_unregister(arg);
> -}
> -
> static int xhci_create_intel_xhci_sw_pdev(struct xhci_hcd *xhci, u32 cap_offset)
> {
> struct usb_hcd *hcd = xhci_to_hcd(xhci);
> struct device *dev = hcd->self.controller;
> struct platform_device *pdev;
> struct resource res = { 0, };
> + struct xhci_pci_priv *priv = (struct xhci_pci_priv *)xhci->priv;
> +
> int ret;
>
> pdev = platform_device_alloc(USB_SW_DRV_NAME, PLATFORM_DEVID_NONE);
> @@ -52,11 +50,7 @@ static int xhci_create_intel_xhci_sw_pdev(struct xhci_hcd *xhci, u32 cap_offset)
> return ret;
> }
>
> - ret = devm_add_action_or_reset(dev, xhci_intel_unregister_pdev, pdev);
> - if (ret) {
> - dev_err(dev, "couldn't add unregister action for intel_xhci_usb_sw pdev\n");
> - return ret;
> - }
> + priv->pdev = pdev;
>
> return 0;
> }
> @@ -88,3 +82,11 @@ int xhci_ext_cap_init(struct xhci_hcd *xhci)
> return 0;
> }
> EXPORT_SYMBOL_GPL(xhci_ext_cap_init);
> +
> +void xhci_ext_cap_remove(struct xhci_hcd *xhci)
> +{
> + struct xhci_pci_priv *priv = (struct xhci_pci_priv *)xhci->priv;
> + if (priv->pdev)
> + platform_device_unregister(priv->pdev);
> +}
> +EXPORT_SYMBOL_GPL(xhci_ext_cap_remove);
> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
> index c2fe218e051f..a4d094df56f7 100644
> --- a/drivers/usb/host/xhci-pci.c
> +++ b/drivers/usb/host/xhci-pci.c
> @@ -14,6 +14,7 @@
> #include <linux/acpi.h>
>
> #include "xhci.h"
> +#include "xhci-pci.h"
> #include "xhci-trace.h"
>
> #define SSIC_PORT_NUM 2
> @@ -62,6 +63,7 @@ static struct hc_driver __read_mostly xhci_pci_hc_driver;
> static int xhci_pci_setup(struct usb_hcd *hcd);
>
> static const struct xhci_driver_overrides xhci_pci_overrides __initconst = {
> + .extra_priv_size = sizeof(struct xhci_pci_priv),
> .reset = xhci_pci_setup,
> };
>
> @@ -393,6 +395,8 @@ static void xhci_pci_remove(struct pci_dev *dev)
> xhci->shared_hcd = NULL;
> }
>
> + xhci_ext_cap_remove(xhci);
> +
> /* Workaround for spurious wakeups at shutdown with HSW */
> if (xhci->quirks & XHCI_SPURIOUS_WAKEUP)
> pci_set_power_state(dev, PCI_D3hot);
> diff --git a/drivers/usb/host/xhci-pci.h b/drivers/usb/host/xhci-pci.h
> new file mode 100644
> index 000000000000..ead9618d7368
> --- /dev/null
> +++ b/drivers/usb/host/xhci-pci.h
> @@ -0,0 +1,19 @@
> +/*
> + * xhci-pci.h - xHCI extended capability handling platform Glue.
> + *
> + * Copyright (C) 2019 Mentor Graphics (Deutschland) GmbH
> + * Derived from xhci-plat.h
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + */
> +
> +#ifndef _XHCI_PCI_H
> +#define _XHCI_PCI_H
> +
> +struct xhci_pci_priv {
> + struct platform_device *pdev;
> +};
> +
> +#endif /* _XHCI_PCI_H */
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index fabbce1c542a..847d2021fc2c 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -2052,6 +2052,7 @@ void xhci_init_driver(struct hc_driver *drv,
> const struct xhci_driver_overrides *over);
> int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id);
> int xhci_ext_cap_init(struct xhci_hcd *xhci);
> +void xhci_ext_cap_remove(struct xhci_hcd *xhci);
>
> int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup);
> int xhci_resume(struct xhci_hcd *xhci, bool hibernated);
>

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