From cee51c33f52ebf673a088a428ac0fecc33ab77fa Mon Sep 17 00:00:00 2001 From: Winter Wang Date: Wed, 27 Jul 2016 10:03:19 +0800 Subject: usb: gadget: configfs: add mutex lock before unregister gadget There may be a race condition if f_fs calls unregister_gadget_item in ffs_closed() when unregister_gadget is called by UDC store at the same time. this leads to a kernel NULL pointer dereference: [ 310.644928] Unable to handle kernel NULL pointer dereference at virtual address 00000004 [ 310.645053] init: Service 'adbd' is being killed... [ 310.658938] pgd = c9528000 [ 310.662515] [00000004] *pgd=19451831, *pte=00000000, *ppte=00000000 [ 310.669702] Internal error: Oops: 817 [#1] PREEMPT SMP ARM [ 310.675211] Modules linked in: [ 310.678294] CPU: 0 PID: 1537 Comm: ->transport Not tainted 4.1.15-03725-g793404c #2 [ 310.685958] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) [ 310.692493] task: c8e24200 ti: c945e000 task.ti: c945e000 [ 310.697911] PC is at usb_gadget_unregister_driver+0xb4/0xd0 [ 310.703502] LR is at __mutex_lock_slowpath+0x10c/0x16c [ 310.708648] pc : [] lr : [] psr: 600f0113 [ 311.565585] [] (usb_gadget_unregister_driver) from [] (unregister_gadget_item+0x1c/0x34) [ 311.575426] [] (unregister_gadget_item) from [] (ffs_closed+0x8c/0x9c) [ 311.583702] [] (ffs_closed) from [] (ffs_data_reset+0xc/0xa0) [ 311.591194] [] (ffs_data_reset) from [] (ffs_data_closed+0x90/0xd0) [ 311.599208] [] (ffs_data_closed) from [] (ffs_ep0_release+0xc/0x14) [ 311.607224] [] (ffs_ep0_release) from [] (__fput+0x80/0x1d0) [ 311.614635] [] (__fput) from [] (task_work_run+0xb0/0xe8) [ 311.621788] [] (task_work_run) from [] (do_work_pending+0x7c/0xa4) [ 311.629718] [] (do_work_pending) from [] (work_pending+0xc/0x20) for functions using functionFS, i.e. android adbd will close /dev/usb-ffs/adb/ep0 when usb IO thread fails, but switch adb from on to off also triggers write "none" > UDC. These 2 operations both call unregister_gadget, which will lead to the panic above. add a mutex before calling unregister_gadget for api used in f_fs. Signed-off-by: Winter Wang Signed-off-by: Felipe Balbi --- drivers/usb/gadget/configfs.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/usb/gadget/configfs.c') diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c index 70cf3477f951..f9237fe2be05 100644 --- a/drivers/usb/gadget/configfs.c +++ b/drivers/usb/gadget/configfs.c @@ -1490,7 +1490,9 @@ void unregister_gadget_item(struct config_item *item) { struct gadget_info *gi = to_gadget_info(item); + mutex_lock(&gi->lock); unregister_gadget(gi); + mutex_unlock(&gi->lock); } EXPORT_SYMBOL_GPL(unregister_gadget_item); -- cgit v1.2.1