If the hub gets disconnected while the core is still activating it, this can result in leaking memory of few USB structures.
This will happen if we have done a kref_get() from hub_activate() and scheduled a delayed work item for HUB_INIT2/3. Now if hub_disconnect() gets called before the delayed work expires, then we will cancel the work from hub_quiesce(), but wouldn't do a kref_put(). And so the unbalance.
kmemleak reports this as (with the commit e50293ef9775 backported to 3.10 kernel with other changes, though the same is true for mainline as well):
unreferenced object 0xffffffc08af5b800 (size 1024): comm "khubd", pid 73, jiffies 4295051211 (age 6482.350s) hex dump (first 32 bytes): 30 68 f3 8c c0 ff ff ff 00 a0 b2 2e c0 ff ff ff 0h.............. 01 00 00 00 00 00 00 00 00 94 7d 40 c0 ff ff ff ..........}@.... backtrace: [<ffffffc0003079ec>] create_object+0x148/0x2a0 [<ffffffc000cc150c>] kmemleak_alloc+0x80/0xbc [<ffffffc000303a7c>] kmem_cache_alloc_trace+0x120/0x1ac [<ffffffc0006fa610>] hub_probe+0x120/0xb84 [<ffffffc000702b20>] usb_probe_interface+0x1ec/0x298 [<ffffffc0005d50cc>] driver_probe_device+0x160/0x374 [<ffffffc0005d5308>] __device_attach+0x28/0x4c [<ffffffc0005d3164>] bus_for_each_drv+0x78/0xac [<ffffffc0005d4ee0>] device_attach+0x6c/0x9c [<ffffffc0005d42b8>] bus_probe_device+0x28/0xa0 [<ffffffc0005d23a4>] device_add+0x324/0x604 [<ffffffc000700fcc>] usb_set_configuration+0x660/0x6cc [<ffffffc00070a350>] generic_probe+0x44/0x84 [<ffffffc000702914>] usb_probe_device+0x54/0x74 [<ffffffc0005d50cc>] driver_probe_device+0x160/0x374 [<ffffffc0005d5308>] __device_attach+0x28/0x4c
Fix this by putting the reference in hub_quiesce() if we canceled a pending work.
CC: stable@vger.kernel.org #4.4+ Fixes: e50293ef9775 ("USB: fix invalid memory access in hub_activate()") Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- Greg,
This is tested over 3.10 with backported patches only, sorry didn't had a mainline setup to test this out. :(
drivers/usb/core/hub.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index bee13517676f..3173693fa8e3 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1315,7 +1315,8 @@ static void hub_quiesce(struct usb_hub *hub, enum hub_quiescing_type type) struct usb_device *hdev = hub->hdev; int i;
- cancel_delayed_work_sync(&hub->init_work); + if (cancel_delayed_work_sync(&hub->init_work)) + kref_put(&hub->kref, hub_release);
/* hub_wq and related activity won't re-trigger */ hub->quiescing = 1;