From 9578569f9a10adcf75a14b8ed2da2e4921e7f8b4 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Wed, 16 Dec 2015 13:32:38 -0500
Subject: [PATCH] USB: fix invalid memory access in hub_activate()
Commit 8520f38099cc ("USB: change hub initialization sleeps to
delayed_work") changed the hub_activate() routine to make part of it
run in a workqueue. However, the commit failed to take a reference to
the usb_hub structure or to lock the hub interface while doing so. As
a result, if a hub is plugged in and quickly unplugged before the work
routine can run, the routine will try to access memory that has been
deallocated. Or, if the hub is unplugged while the routine is
running, the memory may be deallocated while it is in active use.
This patch fixes the problem by taking a reference to the usb_hub at
the start of hub_activate() and releasing it at the end (when the work
is finished), and by locking the hub interface while the work routine
is running. It also adds a check at the start of the routine to see
if the hub has already been disconnected, in which nothing should be
done.
CVE:CVE-2015-8816 Bug:ANDROID-28712303
Change-Id: I4a3e860c0af40b676e420fec8c1980a4e9aba917
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Alexandru Cornea <alexandru.cornea@intel.com>
Tested-by: Alexandru Cornea <alexandru.cornea@intel.com>
Fixes: 8520f38099cc ("USB: change hub initialization sleeps to delayed_work")
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/core/hub.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 8136aea1726c..f015bf81f88a 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -989,6 +989,7 @@ enum hub_activation_type {
static void hub_init_func2(struct work_struct *ws);
static void hub_init_func3(struct work_struct *ws);
+static void hub_release(struct kref *kref);
static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
{
@@ -1001,10 +1002,20 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
unsigned delay;
/* Continue a partial initialization */
- if (type == HUB_INIT2)
- goto init2;
- if (type == HUB_INIT3)
+ if (type == HUB_INIT2 || type == HUB_INIT3) {
+ device_lock(hub->intfdev);
+
+ /* Was the hub disconnected while we were waiting? */
+ if (hub->disconnected) {
+ device_unlock(hub->intfdev);
+ kref_put(&hub->kref, hub_release);
+ return;
+ }
+ if (type == HUB_INIT2)
+ goto init2;
goto init3;
+ }
+ kref_get(&hub->kref);
/* The superspeed hub except for root hub has to use Hub Depth
* value as an offset into the route string to locate the bits
@@ -1209,6 +1220,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
PREPARE_DELAYED_WORK(&hub->init_work, hub_init_func3);
schedule_delayed_work(&hub->init_work,
msecs_to_jiffies(delay));
+ device_unlock(hub->intfdev);
return; /* Continues at init3: below */
} else {
msleep(delay);
@@ -1229,6 +1241,11 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
/* Allow autosuspend if it was suppressed */
if (type <= HUB_INIT3)
usb_autopm_put_interface_async(to_usb_interface(hub->intfdev));
+
+ if (type == HUB_INIT2 || type == HUB_INIT3)
+ device_unlock(hub->intfdev);
+
+ kref_put(&hub->kref, hub_release);
}
/* Implement the continuations for the delays above */
--
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