summaryrefslogtreecommitdiff
path: root/drivers/usb
diff options
context:
space:
mode:
authorAlan Stern <stern@rowland.harvard.edu>2016-06-27 10:23:10 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-06-27 08:39:39 -0700
commitab2a4bf83902c170d29ba130a8abb5f9d90559e1 (patch)
tree36381c0f4f50fff195bcf1d6aa578cc0ff60c940 /drivers/usb
parent7e8b3dfef16375dbfeb1f36a83eb9f27117c51fd (diff)
USB: don't free bandwidth_mutex too early
The USB core contains a bug that can show up when a USB-3 host controller is removed. If the primary (USB-2) hcd structure is released before the shared (USB-3) hcd, the core will try to do a double-free of the common bandwidth_mutex. The problem was described in graphical form by Chung-Geol Kim, who first reported it: ================================================= At *remove USB(3.0) Storage sequence <1> --> <5> ((Problem Case)) ================================================= VOLD ------------------------------------|------------ (uevent) ________|_________ |<1> | |dwc3_otg_sm_work | |usb_put_hcd | |peer_hcd(kref=2)| |__________________| ________|_________ |<2> | |New USB BUS #2 | | | |peer_hcd(kref=1) | | | --(Link)-bandXX_mutex| | |__________________| | ___________________ | |<3> | | |dwc3_otg_sm_work | | |usb_put_hcd | | |primary_hcd(kref=1)| | |___________________| | _________|_________ | |<4> | | |New USB BUS #1 | | |hcd_release | | |primary_hcd(kref=0)| | | | | |bandXX_mutex(free) |<- |___________________| (( VOLD )) ______|___________ |<5> | | SCSI | |usb_put_hcd | |peer_hcd(kref=0) | |*hcd_release | |bandXX_mutex(free*)|<- double free |__________________| ================================================= This happens because hcd_release() frees the bandwidth_mutex whenever it sees a primary hcd being released (which is not a very good idea in any case), but in the course of releasing the primary hcd, it changes the pointers in the shared hcd in such a way that the shared hcd will appear to be primary when it gets released. This patch fixes the problem by changing hcd_release() so that it deallocates the bandwidth_mutex only when the _last_ hcd structure referencing it is released. The patch also removes an unnecessary test, so that when an hcd is released, both the shared_hcd and primary_hcd pointers in the hcd's peer will be cleared. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: Chung-Geol Kim <chunggeol.kim@samsung.com> Tested-by: Chung-Geol Kim <chunggeol.kim@samsung.com> CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/core/hcd.c17
1 files changed, 7 insertions, 10 deletions
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 34b837ae1ed7..d2e3f655c26f 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -2598,26 +2598,23 @@ EXPORT_SYMBOL_GPL(usb_create_hcd);
* Don't deallocate the bandwidth_mutex until the last shared usb_hcd is
* deallocated.
*
- * Make sure to only deallocate the bandwidth_mutex when the primary HCD is
- * freed. When hcd_release() is called for either hcd in a peer set
- * invalidate the peer's ->shared_hcd and ->primary_hcd pointers to
- * block new peering attempts
+ * Make sure to deallocate the bandwidth_mutex only when the last HCD is
+ * freed. When hcd_release() is called for either hcd in a peer set,
+ * invalidate the peer's ->shared_hcd and ->primary_hcd pointers.
*/
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)) {
- kfree(hcd->address0_mutex);
- kfree(hcd->bandwidth_mutex);
- }
if (hcd->shared_hcd) {
struct usb_hcd *peer = hcd->shared_hcd;
peer->shared_hcd = NULL;
- if (peer->primary_hcd == hcd)
- peer->primary_hcd = NULL;
+ peer->primary_hcd = NULL;
+ } else {
+ kfree(hcd->address0_mutex);
+ kfree(hcd->bandwidth_mutex);
}
mutex_unlock(&usb_port_peer_mutex);
kfree(hcd);