On 27.07.2017 05:21, Lu Baolu wrote:
xhci_disable_slot() allows the invoker to pass a command pointer
as paramenter. Otherwise, it will allocate one. This will cause
memory leak when a command structure was allocated inside of this
function while queuing command trb fails. Another problem comes up
when the invoker passed a command pointer, but xhci_disable_slot()
frees it when it detects a dead host.

This patch fixes these two problems by removing the command parameter
from xhci_disable_slot().

Fixes: f9e609b82479 ("usb: xhci: Add helper function xhci_disable_slot().")
Cc: Guoqing Zhang <guoqing.zh...@intel.com>
Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
---
  drivers/usb/host/xhci-hub.c |  2 +-
  drivers/usb/host/xhci.c     | 30 +++++++++---------------------
  drivers/usb/host/xhci.h     |  3 +--
  3 files changed, 11 insertions(+), 24 deletions(-)

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 00721e8..c862d53 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -612,7 +612,7 @@ static int xhci_enter_test_mode(struct xhci_hcd *xhci,
        xhci_dbg(xhci, "Disable all slots\n");
        spin_unlock_irqrestore(&xhci->lock, *flags);
        for (i = 1; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
-               retval = xhci_disable_slot(xhci, NULL, i);
+               retval = xhci_disable_slot(xhci, i);
                if (retval)
                        xhci_err(xhci, "Failed to disable slot %d, %d. Enter test 
mode anyway\n",
                                 i, retval);
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index e69073f..cb2461a 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3519,11 +3519,6 @@ static void xhci_free_dev(struct usb_hcd *hcd, struct 
usb_device *udev)
        struct xhci_virt_device *virt_dev;
        struct xhci_slot_ctx *slot_ctx;
        int i, ret;
-       struct xhci_command *command;
-
-       command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
-       if (!command)
-               return;

  #ifndef CONFIG_USB_DEFAULT_PERSIST
        /*
@@ -3539,10 +3534,8 @@ static void xhci_free_dev(struct usb_hcd *hcd, struct 
usb_device *udev)
        /* If the host is halted due to driver unload, we still need to free the
         * device.
         */
-       if (ret <= 0 && ret != -ENODEV) {
-               kfree(command);
+       if (ret <= 0 && ret != -ENODEV)
                return;
-       }

        virt_dev = xhci->devs[udev->slot_id];
        slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->out_ctx);
@@ -3554,22 +3547,21 @@ static void xhci_free_dev(struct usb_hcd *hcd, struct 
usb_device *udev)
                del_timer_sync(&virt_dev->eps[i].stop_cmd_timer);
        }

-       xhci_disable_slot(xhci, command, udev->slot_id);
+       xhci_disable_slot(xhci, udev->slot_id);
        /*
         * Event command completion handler will free any data structures
         * associated with the slot.  XXX Can free sleep?
         */
  }

-int xhci_disable_slot(struct xhci_hcd *xhci, struct xhci_command *command,
-                       u32 slot_id)
+int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id)
  {
+       struct xhci_command *command;
        unsigned long flags;
        u32 state;
        int ret = 0;

-       if (!command)
-               command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
+       command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
        if (!command)
                return -ENOMEM;

@@ -3588,7 +3580,7 @@ int xhci_disable_slot(struct xhci_hcd *xhci, struct 
xhci_command *command,
                                slot_id);
        if (ret) {
                spin_unlock_irqrestore(&xhci->lock, flags);
-               xhci_dbg(xhci, "FIXME: allocate a command ring segment\n");
+               kfree(command);
                return ret;
        }
        xhci_ring_cmd_db(xhci);
@@ -3663,6 +3655,8 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device 
*udev)
                return 0;
        }

+       xhci_free_command(xhci, command);
+
        if ((xhci->quirks & XHCI_EP_LIMIT_QUIRK)) {
                spin_lock_irqsave(&xhci->lock, flags);
                ret = xhci_reserve_host_control_ep_resources(xhci);
@@ -3698,18 +3692,12 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct 
usb_device *udev)
                pm_runtime_get_noresume(hcd->self.controller);
  #endif

-
-       xhci_free_command(xhci, command);
        /* Is this a LS or FS device under a HS hub? */
        /* Hub or peripherial? */
        return 1;

  disable_slot:
-       /* Disable slot, if we can do it without mem alloc */
-       kfree(command->completion);
-       command->completion = NULL;
-       command->status = 0;
-       return xhci_disable_slot(xhci, command, udev->slot_id);
+       return xhci_disable_slot(xhci, udev->slot_id);

avoiding allocating a new command after failing to allocate a virt dev was
probably the reason why xhci_disable_slot() supported a command
as a parameter in the first place.

But this is such a small corner case, and your patch fixes two more likely 
issues,
and simplifies the code a lot so I think It's well worth it

-Mathias

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