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Subject[PATCH 4.19 50/96] staging: comedi: ni_usb6501: Fix use of uninitialized mutex
Date
From: Ian Abbott <abbotti@mev.co.uk>

commit 660cf4ce9d0f3497cc7456eaa6d74c8b71d6282c upstream.

If `ni6501_auto_attach()` returns an error, the core comedi module code
will call `ni6501_detach()` to clean up. If `ni6501_auto_attach()`
successfully allocated the comedi device private data, `ni6501_detach()`
assumes that a `struct mutex mut` contained in the private data has been
initialized and uses it. Unfortunately, there are a couple of places
where `ni6501_auto_attach()` can return an error after allocating the
device private data but before initializing the mutex, so this
assumption is invalid. Fix it by initializing the mutex just after
allocating the private data in `ni6501_auto_attach()` before any other
errors can be retturned. Also move the call to `usb_set_intfdata()`
just to keep the code a bit neater (either position for the call is
fine).

I believe this was the cause of the following syzbot crash report
<https://syzkaller.appspot.com/bug?extid=cf4f2b6c24aff0a3edf6>:

usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1: config 0 descriptor??
usb 1-1: string descriptor 0 read error: -71
comedi comedi0: Wrong number of endpoints
ni6501 1-1:0.233: driver 'ni6501' 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: 585 Comm: kworker/0:3 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
__mutex_lock_common kernel/locking/mutex.c:925 [inline]
__mutex_lock+0xfe/0x12b0 kernel/locking/mutex.c:1072
ni6501_detach+0x5b/0x110 drivers/staging/comedi/drivers/ni_usb6501.c:567
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+cf4f2b6c24aff0a3edf6@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/ni_usb6501.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/staging/comedi/drivers/ni_usb6501.c
+++ b/drivers/staging/comedi/drivers/ni_usb6501.c
@@ -518,6 +518,9 @@ static int ni6501_auto_attach(struct com
if (!devpriv)
return -ENOMEM;

+ mutex_init(&devpriv->mut);
+ usb_set_intfdata(intf, devpriv);
+
ret = ni6501_find_endpoints(dev);
if (ret)
return ret;
@@ -526,9 +529,6 @@ static int ni6501_auto_attach(struct com
if (ret)
return ret;

- mutex_init(&devpriv->mut);
- usb_set_intfdata(intf, devpriv);
-
ret = comedi_alloc_subdevices(dev, 2);
if (ret)
return ret;

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