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[PATCH] usb: core: fix a double free in the usb driver

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There is a double free problem in the usb driver.
This is caused by delayed deregister for scsi device.
<*> at Insert USB Storage
    -  USB bus #1 register
     usb_create_hcd (primary-kref==1)
     * primary-bandwidth_mutex(alloc))
usb_get_hcd    (primary-kref==2)
    -  USB bus #2 register
usb_create_hcd (second-kref==1)
     * second-bandwidth_mutex==primary-bandwidth_mutex
     usb_get_hcd    (second-kref==2)
    -  scsi_device_get
usb_get_hcd    (second-kref==3)

<*> at remove USB Storage (Normal)
    -  scsi_device_put
usb_put_hcd    (second-kref==2)
    -  USB bus #2 deregister
     usb_release_dev(second-kref==1)
usb_release_dev(second-kref==0)  -> hcd_release()
    -  USB bus #1 deregister
     usb_release_dev(primary-kref==1)
     usb_release_dev(primary-kref==0) -> hcd_release()
*(primary-bandwidth_mutex free)

at remove USB Storage 
    -  USB bus #2 deregister
     usb_release_dev(second-kref==2)
usb_release_dev(second-kref==1)
    -  USB bus #1 deregister
     usb_release_dev(primary-kref==1)
     usb_release_dev(primary-kref==0) -> hcd_release()
     *(primary-bandwidth_mutex free)
    -  scsi_device_put
     usb_put_hcd    (second-kref==0)  -> hcd_release(*)
     * at this, second->primary==0 therefore try to
free the primary-bandwidth_mutex.(already freed)

    To fix this problem kfree(hcd->bandwidth_mutex);
    should be executed at only (hcd->primary_hcd==hcd).

Signed-off-by: Chunggeol Kim 
---
drivers/usb/core/hcd.c |    2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 34b837a..60077f3 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -2608,7 +2608,7 @@ static void hcd_release(struct kref *kref)
struct usb_hcd *hcd = container_of (kref, struct usb_hcd, kref);

mutex_lock(&usb_port_peer_mutex);
- if (usb_hcd_is_primary_hcd(hcd)) {
+ if (hcd == hcd->primary_hcd) {
kfree(hcd->address0_mutex);
kfree(hcd->bandwidth_mutex);
}
-- 
1.7.9.5

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[PATCH] usb: core: fix a double free in the usb driver Chung-Geol Kim <chunggeol.kim@samsung.com> - 2016-05-27 03:40 +0200
  Re: [PATCH] usb: core: fix a double free in the usb driver "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org> - 2016-05-27 06:50 +0200

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