Message-ID: <56E92198.6040501@codeaurora.org>
Date:	Wed, 16 Mar 2016 14:34:24 +0530
From:	Chandra Sekhar Lingutla <clingutla@...eaurora.org>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-msm@...r.kernel.org,
	Russell King <linux@....linux.org.uk>
Subject: Re: Possible race at user mode helper in request_firmware

On 03/16/2016 02:28 PM, Ming Lei wrote:
> On Wed, Mar 16, 2016 at 4:48 PM, Chandra Sekhar Lingutla
> <clingutla@...eaurora.org> wrote:
>> On 03/16/2016 02:12 PM, Ming Lei wrote:
>>>
>>> On Wed, Mar 16, 2016 at 3:02 PM, Chandra Sekhar Lingutla
>>> <clingutla@...eaurora.org> wrote:
>>>>
>>>> Hi Ming,
>>>>
>>>>
>>>> On 03/16/2016 07:36 AM, Ming Lei wrote:
>>>>>
>>>>>
>>>>> On Tue, Mar 15, 2016 at 11:09 PM, Ming Lei <ming.lei@...onical.com>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On Mon, Mar 14, 2016 at 8:00 PM,  <clingutla@...eaurora.org> wrote:
>>>>>>>
>>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> I see possible race in _request_firmware_load function, on which I
>>>>>>> wanted to
>>>>>>> take your opinion.
>>>>>>>
>>>>>>> When system is going to low power mode, device_cache_fw_images() is
>>>>>>> called
>>>>>>> from pm notifier which schedules asynchronous workers to cache devices
>>>>>>> firmware.
>>>>>>> If more than 2 async requests falls under user helper mode, then there
>>>>>>> is a
>>>>>>> use after free of "firmware" directory kobject.
>>>>>>
>>>>>>
>>>>>>
>>>>>> If two requests are for getting same firmware image, only one can be
>>>>>> sent
>>>>>> out and be completed with user helper, please see
>>>>>> fw_lookup_and_allocate_buf(),
>>>>>> so the race shouldn't have been triggered in this case.
>>>>>>
>>>>>> So I guess your test must be involved with at least two different
>>>>>> requests.
>>>>>>
>>>>>>>
>>>>>>> The race will hit, when one asynchronous worker calls device_del()
>>>>>>> while
>>>>>>> other asynchronous worker calls get_device_parent() in
>>>>>>> _request_firmware_load().
>>>>>>> After loading firmware, first worker calls device_del(), and
>>>>>>> "firmware"
>>>>>>> directory ref count is 1, so cleanup_glue_dir() calls kobject_put()
>>>>>>> with
>>>>>>> gdp_mutex lock held.
>>>>>>> Meanwhile, second async worker calls device_add(), and
>>>>>>> get_device_parent()
>>>>>>> is still able to find the firmware directory kobject in ksets after
>>>>>>> getting
>>>>>>> gdp_mutex.
>>>>>>> This kobject gets added as parent to the second device kobject.
>>>>>>> By the time of accessing the parent kobject, its ref count was 0 and
>>>>>>> prints
>>>>>>> below warning stack followed by crash.
>>>>>>
>>>>>>
>>>>>>
>>>>>> The trick here is just that we don't use 'struct device' in
>>>>>> device_cache_fw_images(),
>>>>>> then the firmware device's parent is null during calling device_add()
>>>>>> from
>>>>>> _request_firmware_load(), but this should be allowed by driver core.
>>>>>>
>>>>>>    From firmware class view, both device_add()/device_del() is run with
>>>>>> pair,
>>>>>> and driver core still complains during get_device_parent(), so
>>>>>> something
>>>>>> inside driver core should be be wrong, IMO.
>>>>>
>>>>>
>>>>>
>>>>> Thinking about the issue further, I believe it is a false positive which
>>>>> is
>>>>> caused by CONFIG_DEBUG_KOBJECT_RELEASE, follows the story:
>>>>>
>>>>> 1) device_add() path
>>>>>
>>>>> get_device_parent()
>>>>>                   ......
>>>>>                   mutex_lock(&gdp_mutex);
>>>>>
>>>>>                    /* find our class-directory at the parent and
>>>>> reference
>>>>> it */
>>>>>                    spin_lock(&dev->class->p->glue_dirs.list_lock);
>>>>>                    list_for_each_entry(k, &dev->class->p->glue_dirs.list,
>>>>> entry)
>>>>>                            if (k->parent == parent_kobj) {
>>>>>                                    kobj = kobject_get(k);
>>>>>                                    break;
>>>>>                            }
>>>>>                    spin_unlock(&dev->class->p->glue_dirs.list_lock);
>>>>>                    if (kobj) {
>>>>>                            mutex_unlock(&gdp_mutex);
>>>>>                            return kobj;
>>>>>                    }
>>>>>                    k = class_dir_create_and_add(dev->class, parent_kobj);
>>>>>                    mutex_unlock(&gdp_mutex);
>>>>>                    ......
>>>>>
>>>>> 2) device_del() path
>>>>>
>>>>> cleanup_device_parent()
>>>>>           ->cleanup_glue_dir()
>>>>>                ->mutex_lock(&gdp_mutex);
>>>>>                ->kobject_put(glue_dir);
>>>>>                       ->kobject_cleanup()
>>>>>                             ->kobject_del()
>>>>>                                    ->kobj_kset_leave()
>>>>>                ->mutex_unlock(&gdp_mutex);
>>>>>
>>>>> So gdp_mutex is held wrt. both looking up/adding the parent kobject
>>>>> and removing the parent kobject. Actually with this lock, both glur_dir
>>>>> kobject's referece counting and joining/leaving kset are run atomically.
>>>>>
>>>>> The race you found is triggered by CONFIG_DEBUG_KOBJECT_RELEASE,
>>>>> which causes kobject_cleanup() to be run in workqueue context and the
>>>>> lock of gdp_mutex can't be hold in that situation anymore. That is the
>>>>> root
>>>>> cause for your race.
>>>>>
>>>>> That also said DEBUG_KOBJECT_RELEASE might cause trouble in
>>>>> some situations.
>>>>>
>>>>> Thanks,
>>>>> Ming
>>>>>
>>>> I agree that, CONFIG_DEBUG_KOBJECT_RELEASE can cause the race, as it
>>>> delays
>>>> call to kobject_cleanup() which deletes kobj entry in glue_dir list.
>>>>
>>>> I see the race even after disabling CONFIG_DEBUG_KOBJECT_RELEASE.
>>>>
>>>> The race is between kobject_put() and kobject_get() for the "firmware"
>>>> directory.
>>>>
>>>> In  device_del() path, I see the race after the call of
>>>> cleanup_device_parent().
>>>> cleanup_device_parent() calls kobject_put(glue_dir) with gdp_mutex lock
>>>> holding,
>>>> So ideally, to call kobject_put/kobject_get(glue_dir) we need to acquire
>>>> gdp_mutex.
>>>>
>>>> but kobject_del(kobj) will not hold the gdp_mutex lock while calling
>>>> kobject_put(kobj->parent).
>>>>
>>>> Here is the race:
>>>>
>>>> Consider 2 async works calls request_firmware() for 2 different binaries
>>>> (fw1.bin, fw2.bin)
>>>> Async work1 got scheduled first, and it falls in user helper mode so it
>>>> creates "firmware" dir
>>>> and then creates "fw1.bin" directory to load data from user.
>>>> After load completion or timeout, it starts cleanup dir's, meantime async
>>>> work2 got scheduled and
>>>> it also falls in user helper mode, and story starts here:
>>>>
>>>> PATH1   req fw for "fw1.bin"
>>>> PATH2
>>>>    req fw for "fw2.bin"
>>>> _request_firmware_load()
>>>> device_del(dev1)
>>>>
>>>>           ->cleanup_device_parent()
>>>>
>>>>                   mutex_lock(&gdp_mutex);
>>>>
>>>> _request_firmware_load("fw2.bin")
>>>>                   kobject_put(kobj->parent); --> firmware ref ->1
>>>>                    ->device_add(dev2)
>>>>                   mutex_unlock(&gdp_mutex);
>>>> ->get_device_parent()
>>>>           ->kobject_del()
>>>> mutex_lock(&gdp_mutex)
>>>>                   kobj_kset_leave(kobj); -->del "fw1.bin" kobj in kset
>>>> list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry)
>>>>                   kobject_put(kobj->parent); /* No lock :)*/
>>>> if (k->parent == parent_kobj) {
>>>>
>>>>                           ->kref_put()    --> firmware ref ->0
>>>> kobj = kobject_get(k); -> k is "firmware"
>>>>    dir
>>>>                                   ->kboject_release()
>>>> break;
>>>>
>>>>                                           ->kobject_del()
>>>> }
>>>>
>>>>                                   /*here deletes firmware entry in kset*/
>>>> mutex_unlock(&gdp_mutex)
>>>>
>>>> ->dev2->kobj.parent = kobj    -> kobj is released already
>>>>
>>>>
>>>>
>>>> PATH 1 is started removing the kobject of "fw1.bin" and its parent
>>>> "firmware"
>>>> .
>>>> cleanup_device_parent(dev1) makes firmware ref count to 1, by calling
>>>> kobject_put(firmware) with gdp_mutex held.
>>>>
>>>> and kobject_del(dev1->kobj) will again calls kobject_put(kobj->parent)
>>>> without holding gdp_mutex.
>>>>
>>>> In PATH2, glue_dir is able to find "firmware" kobj, as firmware dir kobj
>>>> is
>>>> deleted from the glue_dir list at kboject_release().
>>>> and it calls kobject_get(firmware), by the time PATH1 calls
>>>> kobject_release(firmware).
>>>>
>>>> So PATH2 got reference of freed firmware kobj and added as parent to
>>>> "fw2.bin" kobj.
>>>>
>>>> I think, here is possible fix for this race:
>>>>
>>>> ------------------------8<-------------------------------------
>>>> Signed-off-by: Lingutla Chandrasekhar <clingutla@...eaurora.org>
>>>>
>>>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>>>> index 5d8b713..47bc082 100644
>>>> --- a/drivers/base/core.c
>>>> +++ b/drivers/base/core.c
>>>> @@ -1224,7 +1224,13 @@ void device_del(struct device *dev)
>>>>                                                BUS_NOTIFY_REMOVED_DEVICE,
>>>> dev);
>>>>           kobject_uevent(&dev->kobj, KOBJ_REMOVE);
>>>>           cleanup_device_parent(dev);
>>>> -       kobject_del(&dev->kobj);
>>>> +
>>>> +       if (dev->kobj.parent->kset == &dev->class->p->glue_dirs) {
>>>> +               mutex_lock(&gdp_mutex);
>>>> +               kobject_del(&dev->kobj);
>>>> +               mutex_unlock(&gdp_mutex);
>>>> +       } else
>>>> +               kobject_del(&dev->kobj);
>>>>           put_device(parent);
>>>>    }
>>>>    EXPORT_SYMBOL_GPL(device_del);
>>>>
>>>> --------------------------->8-----------------------------------
>>>
>>>
>>> OK, one simpler way is to move cleanup_device_parent(dev)
>>> after kobject_del(&dev->kobj), which looks more clean too.
>>>
>> No, We can't move that, bcz kobject_del(&dev->kobj) will clear the parent.
>
> Yeah, but I think it is better to do that and just call
> cleanup_glue_dir() directly
> because cleanup_device_parent() should have released the glue_dir.
>
> BTW, failure path of device_add() has been broken already.
>
Yah, forgot to mention that. we need to reorder like above fix, can we?.

>>
>>
>>>>
>>>>
>>>>>>
>>>>>>>
>>>>>>> [21147.455038] ------------[ cut here ]------------
>>>>>>> [21147.458910] WARNING: at <...>/kernel/include/linux/kref.h:47
>>>>>>> kobject_get+0x50/0x68()
>>>>>>> [21147.481199] Modules linked in: core_ctl(PO) qdrbg_module(O)
>>>>>>> qcrypto_module(O)
>>>>>>> [21147.481256] CPU: 2 PID: 23935 Comm: kworker/u16:8 Tainted: P W O
>>>>>>> 3.10.84-g0957845-00427-g56a05c2 #1
>>>>>>> [21147.481284] Workqueue: events_unbound async_run_entry_fn
>>>>>>> [21147.481296] Call trace:
>>>>>>> [21147.481315] [<ffffffc000206b60>] dump_backtrace+0x0/0x270
>>>>>>> [21147.481331] [<ffffffc000206de0>] show_stack+0x10/0x1c
>>>>>>> [21147.481353] [<ffffffc000d569ec>] dump_stack+0x1c/0x28
>>>>>>> [21147.481370] [<ffffffc00021cc18>] warn_slowpath_common+0x74/0x9c
>>>>>>> [21147.481383] [<ffffffc00021ce4c>] warn_slowpath_null+0x14/0x20
>>>>>>> [21147.481397] [<ffffffc000456b10>] kobject_get+0x4c/0x68
>>>>>>> [21147.481416] [<ffffffc000609f64>] get_device_parent+0xa0/0x194
>>>>>>> [21147.481430] [<ffffffc00060a3f4>] device_add+0x100/0x600
>>>>>>> [21147.481446] [<ffffffc00061c390>] _request_firmware+0x8b4/0xa80
>>>>>>> [21147.481459] [<ffffffc00061c58c>] request_firmware+0x30/0x3c
>>>>>>> [21147.481473] [<ffffffc00061c5ec>] cache_firmware+0x54/0xb0
>>>>>>> [21147.481490] [<ffffffc00061c65c>]
>>>>>>> __async_dev_cache_fw_image+0x14/0x54
>>>>>>> [21147.481505] [<ffffffc000243794>] async_run_entry_fn+0x6c/0x12c
>>>>>>> [21147.481521] [<ffffffc000237e88>] process_one_work+0x264/0x3dc
>>>>>>> [21147.481535] [<ffffffc0002392c0>] worker_thread+0x1f0/0x340
>>>>>>> [21147.481553] [<ffffffc00023e500>] kthread+0xac/0xb8
>>>>>>> [21147.481563] ---[ end trace dabc98ea48b8ba59 ]---
>>>>>>>
>>>>>>> [21147.486436] Unable to handle kernel paging request at virtual
>>>>>>> address
>>>>>>> 0x6b6b6b6b6b6b6bcb
>>>>>>> [21147.493816] pgd = ffffffc0a982d000
>>>>>>> [21147.498337] [6b6b6b6b6b6b6bcb] *pgd=0000000000000000
>>>>>>> [21147.502287] Internal error: Oops: 96000004 [#1] PREEMPT SMP
>>>>>>> [21147.507826] Modules linked in: core_ctl(PO) qdrbg_module(O)
>>>>>>> qcrypto_module(O)
>>>>>>> [21147.514951] CPU: 2 PID: 23935 Comm: kworker/u16:8 Tainted: P W O
>>>>>>> 3.10.84-g0957845-00427-g56a05c2 #1
>>>>>>> [21147.524686] Workqueue: events_unbound async_run_entry_fn
>>>>>>> [21147.529965] task: ffffffc008138000 ti: ffffffc007880000 task.ti:
>>>>>>> ffffffc007880000
>>>>>>> [21147.537438] PC is at sysfs_create_dir+0x34/0xd4
>>>>>>> [21147.541949] LR is at kobject_add_internal+0x120/0x24c
>>>>>>> [21147.546979] pc : [<ffffffc000361fa8>] lr : [<ffffffc000456f5c>]
>>>>>>> pstate:
>>>>>>> 80000145
>>>>>>> [21147.996295] Process kworker/u16:8 (pid: 23935, stack limit =
>>>>>>> 0xffffffc007880058)
>>>>>>> [21148.003673] Call trace:
>>>>>>> [21148.006117] [<ffffffc000361fa8>] sysfs_create_dir+0x34/0xd4
>>>>>>> [21148.011663] [<ffffffc000456f58>] kobject_add_internal+0x11c/0x24c
>>>>>>> [21148.017737] [<ffffffc0004573ec>] kobject_add+0xc8/0xe4
>>>>>>> [21148.022863] [<ffffffc00060a410>] device_add+0x11c/0x600
>>>>>>> [21148.028069] [<ffffffc00061c390>] _request_firmware+0x8b4/0xa80
>>>>>>> [21148.033886] [<ffffffc00061c58c>] request_firmware+0x30/0x3c
>>>>>>> [21148.039439] [<ffffffc00061c5ec>] cache_firmware+0x54/0xb0
>>>>>>> [21148.044822] [<ffffffc00061c65c>]
>>>>>>> __async_dev_cache_fw_image+0x14/0x54
>>>>>>> [21148.051249] [<ffffffc000243794>] async_run_entry_fn+0x6c/0x12c
>>>>>>> [21148.057064] [<ffffffc000237e88>] process_one_work+0x264/0x3dc
>>>>>>> [21148.062792] [<ffffffc0002392c0>] worker_thread+0x1f0/0x340
>>>>>>> [21148.068263] [<ffffffc00023e500>] kthread+0xac/0xb8
>>>>>>> [21148.073039] Code: b5000094 14000026 d000ac54 9125a294 (7940c281)
>>>>>>> [21148.080312] ---[ end trace dabc98ea48b8ba5a ]---
>>>>>>>
>>>>>>> Below is the callstack where the parent is freed from the slub_debug
>>>>>>> info.
>>>>>>> 0xFFFFFFC000608D74  \\vmlinux\base/core\class_dir_release+0x0C
>>>>>>> 0xFFFFFFC0002FE6BC \\vmlinux\slub\free_debug_processing\fail+0x114
>>>>>>> 0xFFFFFFC0002FE7A0 \\vmlinux\slub\__slab_free+0x44
>>>>>>> 0xFFFFFFC0002FEE60 \\vmlinux\slub\kfree+0x1F8
>>>>>>> 0xFFFFFFC000608D70 \\vmlinux\base/core\class_dir_release+0x8
>>>>>>> 0xFFFFFFC000456D70 \\vmlinux\kobject\kobject_release+0x134
>>>>>>> 0xFFFFFFC000456E10 \\vmlinux\kobject\kobject_put+0x58
>>>>>>> 0xFFFFFFC000456C28 \\vmlinux\kobject\kobject_del+0x64
>>>>>>> 0xFFFFFFC000609D78 \\vmlinux\base/core\device_del+0x150
>>>>>>> 0xFFFFFFC00061C524
>>>>>>> \\vmlinux\firmware_class\_request_firmware\out+0x71C
>>>>>>> 0xFFFFFFC00061C58C \\vmlinux\firmware_class\request_firmware+0x30
>>>>>>> 0xFFFFFFC00061C5EC \\vmlinux\firmware_class\cache_firmware+0x54
>>>>>>> 0xFFFFFFC00061C65C
>>>>>>> \\vmlinux\firmware_class\__async_dev_cache_fw_image+0x14
>>>>>>> 0xFFFFFFC000243794 \\vmlinux\async\async_run_entry_fn+0x6C
>>>>>>> 0xFFFFFFC000237E88 \\vmlinux\workqueue\process_one_work+0x264
>>>>>>> 0xFFFFFFC0002392C0 \\vmlinux\workqueue\worker_thread\recheck+0x1A0
>>>>>>> 0xFFFFFFC00023E500 \\vmlinux\kthread\kthread+0xAC
>>>>>>>
>>>>>>> For similar type of issue, I see there is an existing fix: "sysfs:
>>>>>>> driver
>>>>>>> core: Fix glue dir race condition by gdp_mutex".
>>>>>>>
>>>>>>>
>>>>>>> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/base/core.c?id=e4a60d139060975eb956717e4f63ae348d4d8cc5
>>>>>>>
>>>>>>> Still I am able to reproduce the issue. I have verified this race on
>>>>>>> kernels: 3.10, 3.18 and 4.4.
>>>>>>>
>>>>>>> I followed below procedure to reproduce the issue:
>>>>>>>         1. Enable "CONFIG_DEBUG_KOBJECT_RELEASE"
>>>>>>>         2. Use test_firmware, modified the test for async calls
>>>>>>>         3. Replace WARN_ON with BUG_ON in kref_get().
>>>>>>> I ran below script from shell:
>>>>>>>        count=0
>>>>>>>        while [ 1 ]
>>>>>>>        do
>>>>>>>                echo 3 >
>>>>>>> /sys/devices/virtual/misc/test_firmware/trigger_ufw
>>>>>>>                if [ $? -ne 0 ]; then
>>>>>>>                        print "Exiting.. "
>>>>>>>                        exit 1
>>>>>>>                fi
>>>>>>>                count=$(($count +1))
>>>>>>>                echo "count $count"
>>>>>>>         done
>>>>>>>
>>>>>>> With below patch, I could reproduce the issue in the 2nd iteration.
>>>>>>
>>>>>>
>>>>>>
>>>>>> I will run your test script to see if there is new findings.
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> -------------------------8<----------------------------------------------
>>>>>>>
>>>>>>> To reproduce the race condition, use firmware test and
>>>>>>> CONFIG_DEBUG_KOBJECT_RELEASE=y, which delays kobject
>>>>>>> releases. So that we can catch the bug easily.
>>>>>>>
>>>>>>> Enabled below flags in kernel config file:
>>>>>>>
>>>>>>> +CONFIG_DEBUG_KOBJECT_RELEASE=y
>>>>>>> +CONFIG_TEST_FIRMWARE=y
>>>>>>
>>>>>>
>>>>>>
>>>>>> Looks I can't reproduce the issue with your approach.
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> diff --git a/include/linux/kref.h b/include/linux/kref.h
>>>>>>> index 484604d..727fb24 100644
>>>>>>> --- a/include/linux/kref.h
>>>>>>> +++ b/include/linux/kref.h
>>>>>>> @@ -44,7 +44,7 @@ static inline void kref_get(struct kref *kref)
>>>>>>>          * condition when this kref is freeing by some other thread
>>>>>>> right
>>>>>>> now.
>>>>>>>          * In this case one should use kref_get_unless_zero()
>>>>>>>          */
>>>>>>> -    WARN_ON_ONCE(atomic_inc_return(&kref->refcount) < 2);
>>>>>>> +    BUG_ON(atomic_inc_return(&kref->refcount) < 2);
>>>>>>>     }
>>>>>>>
>>>>>>>     /**
>>>>>>> diff --git a/lib/test_firmware.c b/lib/test_firmware.c
>>>>>>> old mode 100644
>>>>>>> new mode 100755
>>>>>>> index 86374c1..14c9598
>>>>>>> --- a/lib/test_firmware.c
>>>>>>> +++ b/lib/test_firmware.c
>>>>>>> @@ -18,6 +18,7 @@
>>>>>>>     #include <linux/miscdevice.h>
>>>>>>>     #include <linux/slab.h>
>>>>>>>     #include <linux/uaccess.h>
>>>>>>> +#include <linux/async.h>
>>>>>>>
>>>>>>> +
>>>>>>> +static ASYNC_DOMAIN_EXCLUSIVE(ufw_domain);
>>>>>>> +
>>>>>>> +static void __async_ufw_work(void *name,
>>>>>>> +                                       async_cookie_t cookie)
>>>>>>> +{
>>>>>>> +    const struct firmware *fw;
>>>>>>> +    const char *fw_name = name;
>>>>>>> +    int ret;
>>>>>>> +
>>>>>>> +    pr_err("requesting %s\n", fw_name);
>>>>>>> +
>>>>>>> +    ret = request_firmware(&fw, fw_name, NULL);
>>>>>>> +    pr_err("loaded: %zu\n", fw ? fw->size : 0);
>>>>>>> +        if (!ret)
>>>>>>> +                kfree(fw);
>>>>>>> +
>>>>>>> +}
>>>>>>> +
>>>>>>> +static char *name[] = { "fw1.bin", "fw2.bin"};
>>>>>>> +
>>>>>>> +static ssize_t trigger_ufw_store(struct device *dev,
>>>>>>> +        struct device_attribute *attr,
>>>>>>> +        const char *buf, size_t count)
>>>>>>> +{
>>>>>>> +    int rc, i, c=0;
>>>>>>> +    u32 start;
>>>>>>> +    char *fw_name;
>>>>>>> +
>>>>>>> +    rc = kstrtou32(buf, 0, &start);
>>>>>>> +    if (rc){
>>>>>>> +        pr_err("Invalid option\n");
>>>>>>> +        return rc;
>>>>>>> +    }
>>>>>>> +    pr_err(" no of iterations %d\n", start);
>>>>>>> +
>>>>>>> +    for (i=0; i< start; i++)
>>>>>>> +    {
>>>>>>> +        if (c >= 2)
>>>>>>> +            c = 0;
>>>>>>> +        fw_name = name[c++];
>>>>>>> +        async_schedule_domain(__async_ufw_work, (void *)fw_name,
>>>>>>> &ufw_domain);
>>>>>>> +    }
>>>>>>> +    async_synchronize_full_domain(&ufw_domain);
>>>>>>> +    return count;
>>>>>>> +}
>>>>>>>
>>>>>>>     static DEVICE_ATTR_WO(trigger_request);
>>>>>>> +static DEVICE_ATTR_WO(trigger_ufw);
>>>>>>>
>>>>>>>     static int __init test_firmware_init(void)
>>>>>>>     {
>>>>>>> @@ -92,6 +140,12 @@ static int __init test_firmware_init(void)
>>>>>>>             goto dereg;
>>>>>>>         }
>>>>>>>
>>>>>>> +    rc = device_create_file(test_fw_misc_device.this_device,
>>>>>>> +                             &dev_attr_trigger_ufw);
>>>>>>> +    if (rc) {
>>>>>>> +        pr_err("could not create sysfs interface: %d\n", rc);
>>>>>>> +        goto dereg;
>>>>>>> +    }
>>>>>>>         pr_warn("interface ready\n");
>>>>>>>
>>>>>>>         return 0;
>>>>>>> @@ -106,7 +160,9 @@ static void __exit test_firmware_exit(void)
>>>>>>>     {
>>>>>>>         release_firmware(test_firmware);
>>>>>>>         device_remove_file(test_fw_misc_device.this_device,
>>>>>>> -               &dev_attr_trigger_request);
>>>>>>> +            &dev_attr_trigger_request);
>>>>>>> +    device_remove_file(test_fw_misc_device.this_device,
>>>>>>> +            &dev_attr_trigger_ufw);
>>>>>>>         misc_deregister(&test_fw_misc_device);
>>>>>>>         pr_warn("removed interface\n");
>>>>>>>     }
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ----------------------------8<--------------------------------------------
>>>>>>>
>>>>>>> Thanks and regards,
>>>>>>> Chandrasekhar L.
>>>>>>> --
>>>>>>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
>>>>>>> member of
>>>>>>> Code Aurora Forum,
>>>>>>>     a Linux Foundation Collaborative Project.

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