From 6bb47e8ab98accb1319bd43c64966340ba3bba9a Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Thu, 4 Aug 2016 13:32:22 -0700 Subject: usb: hub: Fix unbalanced reference count/memory leak/deadlocks Memory leak and unbalanced reference count: 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: [] create_object+0x148/0x2a0 [] kmemleak_alloc+0x80/0xbc [] kmem_cache_alloc_trace+0x120/0x1ac [] hub_probe+0x120/0xb84 [] usb_probe_interface+0x1ec/0x298 [] driver_probe_device+0x160/0x374 [] __device_attach+0x28/0x4c [] bus_for_each_drv+0x78/0xac [] device_attach+0x6c/0x9c [] bus_probe_device+0x28/0xa0 [] device_add+0x324/0x604 [] usb_set_configuration+0x660/0x6cc [] generic_probe+0x44/0x84 [] usb_probe_device+0x54/0x74 [] driver_probe_device+0x160/0x374 [] __device_attach+0x28/0x4c Deadlocks: If the hub gets disconnected early enough (i.e. before INIT2/INIT3 are finished and the init_work is still queued), the core may call hub_quiesce() after acquiring interface device locks and it will wait for the work to be cancelled synchronously. But if the work handler is already running in parallel, it may try to acquire the same interface device lock and this may result in deadlock. Fix both the issues by removing the call to cancel_delayed_work_sync(). CC: #4.4+ Fixes: e50293ef9775 ("USB: fix invalid memory access in hub_activate()") Reported-by: Manu Gautam Signed-off-by: Viresh Kumar Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'drivers/usb/core/hub.c') diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index bee13517676f..3ccffac0f647 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1315,8 +1315,6 @@ 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); - /* hub_wq and related activity won't re-trigger */ hub->quiescing = 1; -- cgit v1.2.3 From ca5cbc8b02f9b21cc8cd1ab36668763ec34f9ee8 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 5 Aug 2016 11:49:45 -0400 Subject: USB: hub: fix up early-exit pathway in hub_activate The early-exit pathway in hub_activate, added by commit e50293ef9775 ("USB: fix invalid memory access in hub_activate()") needs improvement. It duplicates code that is already present at the end of the subroutine, and it neglects to undo the effect of a usb_autopm_get_interface_no_resume() call. This patch fixes both problems by making the early-exit pathway jump directly to the end of the subroutine. It simplifies the code at the end by merging two conditionals that actually test the same condition although they appear different: If type < HUB_INIT3 then type must be either HUB_INIT2 or HUB_INIT, and it can't be HUB_INIT because in that case the subroutine would have exited earlier. Signed-off-by: Alan Stern CC: #4.4+ Reviewed-by: Viresh Kumar Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) (limited to 'drivers/usb/core/hub.c') diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 3ccffac0f647..bb69d262b6f9 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1055,11 +1055,8 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) 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 (hub->disconnected) + goto disconnected; if (type == HUB_INIT2) goto init2; goto init3; @@ -1281,12 +1278,12 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) /* Scan all ports that need attention */ kick_hub_wq(hub); - /* Allow autosuspend if it was suppressed */ - if (type <= HUB_INIT3) + if (type == HUB_INIT2 || type == HUB_INIT3) { + /* Allow autosuspend if it was suppressed */ + disconnected: 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); } -- cgit v1.2.3 From 07d316a22e119fa301fd7dba7f1e1adfd4f72c05 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 5 Aug 2016 11:51:30 -0400 Subject: USB: hub: change the locking in hub_activate The locking in hub_activate() is not adequate to provide full mutual exclusion with hub_quiesce(). The subroutine locks the hub's usb_interface, but the callers of hub_quiesce() (such as hub_pre_reset() and hub_event()) hold the lock to the hub's usb_device. This patch changes hub_activate() to make it acquire the same lock as those other routines. Signed-off-by: Alan Stern CC: #4.4+ Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/usb/core/hub.c') diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index bb69d262b6f9..1d5fc32d06d0 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1052,7 +1052,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) /* Continue a partial initialization */ if (type == HUB_INIT2 || type == HUB_INIT3) { - device_lock(hub->intfdev); + device_lock(&hdev->dev); /* Was the hub disconnected while we were waiting? */ if (hub->disconnected) @@ -1259,7 +1259,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) queue_delayed_work(system_power_efficient_wq, &hub->init_work, msecs_to_jiffies(delay)); - device_unlock(hub->intfdev); + device_unlock(&hdev->dev); return; /* Continues at init3: below */ } else { msleep(delay); @@ -1282,7 +1282,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) /* Allow autosuspend if it was suppressed */ disconnected: usb_autopm_put_interface_async(to_usb_interface(hub->intfdev)); - device_unlock(hub->intfdev); + device_unlock(&hdev->dev); } kref_put(&hub->kref, hub_release); -- cgit v1.2.3