diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2016-06-27 10:23:10 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-03-26 12:13:17 +0200 |
| commit | 45d9558837d4d79e6d241f1c45cabea8d20dca22 (patch) | |
| tree | 5828c62453a3fdb0a4641c85ecfe72c09d574959 | |
| parent | ac1a97d8a562161e42edd23e5d0f1740a3d93c85 (diff) | |
USB: don't free bandwidth_mutex too early
commit ab2a4bf83902c170d29ba130a8abb5f9d90559e1 upstream.
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: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/core/hcd.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index 9a5303c17de7..5724d7c41e29 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -2573,26 +2573,23 @@ 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); |