This is a note to let you know that I've just added the patch titled

staging: comedi: vmk80xx: Fix use of uninitialized semaphore

to my staging git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 08b7c2f9208f0e2a32159e4e7a4831b7adb10a3e Mon Sep 17 00:00:00 2001

From: Ian Abbott abbotti@mev.co.uk Date: Mon, 15 Apr 2019 12:10:14 +0100 Subject: staging: comedi: vmk80xx: Fix use of uninitialized semaphore

If `vmk80xx_auto_attach()` returns an error, the core comedi module code will call `vmk80xx_detach()` to clean up. If `vmk80xx_auto_attach()` successfully allocated the comedi device private data, `vmk80xx_detach()` assumes that a `struct semaphore limit_sem` contained in the private data has been initialized and uses it. Unfortunately, there are a couple of places where `vmk80xx_auto_attach()` can return an error after allocating the device private data but before initializing the semaphore, so this assumption is invalid. Fix it by initializing the semaphore just after allocating the private data in `vmk80xx_auto_attach()` before any other errors can be returned.

I believe this was the cause of the following syzbot crash report https://syzkaller.appspot.com/bug?extid=54c2f58f15fe6876b6ad:

usb 1-1: config 0 has no interface number 0 usb 1-1: New USB device found, idVendor=10cf, idProduct=8068, bcdDevice=e6.8d usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 usb 1-1: config 0 descriptor?? vmk80xx 1-1:0.117: driver 'vmk80xx' failed to auto-configure device. INFO: trying to register non-static key. the code is fine but needs lockdep annotation. turning off the locking correctness validator. CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc4-319354-g9a33b36 #3 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usb_hub_wq hub_event Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xe8/0x16e lib/dump_stack.c:113 assign_lock_key kernel/locking/lockdep.c:786 [inline] register_lock_class+0x11b8/0x1250 kernel/locking/lockdep.c:1095 __lock_acquire+0xfb/0x37c0 kernel/locking/lockdep.c:3582 lock_acquire+0x10d/0x2f0 kernel/locking/lockdep.c:4211 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x44/0x60 kernel/locking/spinlock.c:152 down+0x12/0x80 kernel/locking/semaphore.c:58 vmk80xx_detach+0x59/0x100 drivers/staging/comedi/drivers/vmk80xx.c:829 comedi_device_detach+0xed/0x800 drivers/staging/comedi/drivers.c:204 comedi_device_cleanup.part.0+0x68/0x140 drivers/staging/comedi/comedi_fops.c:156 comedi_device_cleanup drivers/staging/comedi/comedi_fops.c:187 [inline] comedi_free_board_dev.part.0+0x16/0x90 drivers/staging/comedi/comedi_fops.c:190 comedi_free_board_dev drivers/staging/comedi/comedi_fops.c:189 [inline] comedi_release_hardware_device+0x111/0x140 drivers/staging/comedi/comedi_fops.c:2880 comedi_auto_config.cold+0x124/0x1b0 drivers/staging/comedi/drivers.c:1068 usb_probe_interface+0x31d/0x820 drivers/usb/core/driver.c:361 really_probe+0x2da/0xb10 drivers/base/dd.c:509 driver_probe_device+0x21d/0x350 drivers/base/dd.c:671 __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778 bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454 __device_attach+0x223/0x3a0 drivers/base/dd.c:844 bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514 device_add+0xad2/0x16e0 drivers/base/core.c:2106 usb_set_configuration+0xdf7/0x1740 drivers/usb/core/message.c:2021 generic_probe+0xa2/0xda drivers/usb/core/generic.c:210 usb_probe_device+0xc0/0x150 drivers/usb/core/driver.c:266 really_probe+0x2da/0xb10 drivers/base/dd.c:509 driver_probe_device+0x21d/0x350 drivers/base/dd.c:671 __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778 bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454 __device_attach+0x223/0x3a0 drivers/base/dd.c:844 bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514 device_add+0xad2/0x16e0 drivers/base/core.c:2106 usb_new_device.cold+0x537/0xccf drivers/usb/core/hub.c:2534 hub_port_connect drivers/usb/core/hub.c:5089 [inline] hub_port_connect_change drivers/usb/core/hub.c:5204 [inline] port_event drivers/usb/core/hub.c:5350 [inline] hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432 process_one_work+0x90f/0x1580 kernel/workqueue.c:2269 worker_thread+0x9b/0xe20 kernel/workqueue.c:2415 kthread+0x313/0x420 kernel/kthread.c:253 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Reported-by: syzbot+54c2f58f15fe6876b6ad@syzkaller.appspotmail.com Signed-off-by: Ian Abbott abbotti@mev.co.uk Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/staging/comedi/drivers/vmk80xx.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/comedi/drivers/vmk80xx.c b/drivers/staging/comedi/drivers/vmk80xx.c index 6234b649d887..b035d662390b 100644 --- a/drivers/staging/comedi/drivers/vmk80xx.c +++ b/drivers/staging/comedi/drivers/vmk80xx.c @@ -800,6 +800,8 @@ static int vmk80xx_auto_attach(struct comedi_device *dev,

devpriv->model = board->model;

+ sema_init(&devpriv->limit_sem, 8); + ret = vmk80xx_find_usb_endpoints(dev); if (ret) return ret; @@ -808,8 +810,6 @@ static int vmk80xx_auto_attach(struct comedi_device *dev, if (ret) return ret;

- sema_init(&devpriv->limit_sem, 8); - usb_set_intfdata(intf, devpriv);

if (devpriv->model == VMK8055_MODEL)