[PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[Pei Xiao]

The function new_device_store() calls driver_find() without any
protection against concurrent driver unregistration. This can lead
to a use-after-free (UAF) when a driver is unloaded (via rmmod)
in parallel with a new device addition via sysfs.

The race window exists because driver_find() returns a pointer to
the driver's private data, but does not increase its reference
count. The caller is responsible for ensuring the driver remains
valid, but new_device_store() did not hold any lock or reference
during the lookup and subsequent use.

Concurrently, pata_parport_unregister_driver() releases the
pi_mutex before calling driver_unregister(), allowing new_device_store
to proceed with a stale pointer after the driver has been freed.

Fix this by expanding the critical section protected by pi_mutex
in both functions:

- In new_device_store(): acquire pi_mutex before calling driver_find(),
  and keep it held until all uses of the found driver pointer are
  completed.
- In pata_parport_unregister_driver(): hold pi_mutex throughout the
  entire unregistration process, including the driver_unregister()
  call, so that no concurrent lookup can see a partially removed
  driver.

Thread A (new_device_store)       | Thread B (pata_parport_unregister_driver)
  driver_find("aten")             |
                                  |   mutex_lock(&pi_mutex)
                                  |   idr_remove(&protocols, id)
                                  |   mutex_unlock(&pi_mutex)
                                  |   driver_unregister(&pr->driver)
                                  |   (frees driver_private)
  /* continues using stale driv */|
  -> UAF!                         |

Logs:
BUG: KASAN: slab-use-after-free in driver_find+0xd0/0xd4
Read of size 8 at addr ffffff9f970dc690 by task sh/4737
Call trace:
 show_stack+0x14/0x1c (C)
 dump_stack_lvl+0x70/0x84
 print_report+0xf4/0x5a4
 kasan_report+0xa0/0xe4
 __asan_report_load8_noabort+0x18/0x20
 driver_find+0xd0/0xd4
 new_device_store+0x140/0x30c [pata_parport]
 bus_attr_store+0x5c/0x94
 sysfs_kf_write+0x1c4/0x25c
 ...

Allocated by task 4734:
 kasan_save_stack+0x28/0x4c
 kasan_save_track+0x1c/0x34
 kasan_save_alloc_info+0x3c/0x4c
 __kasan_kmalloc+0x98/0xac
 __kmalloc_cache_noprof+0x158/0x3cc
 bus_add_driver+0x70/0x4d8
 driver_register+0xf0/0x3b0
 pata_parport_register_driver+0xb8/0x1c4 [pata_parport]
 0xffffffc07f5ce014
 do_one_initcall+0xb8/0x36c
 do_init_module+0x230/0x6d4
 ...

Freed by task 4737:
 kasan_save_stack+0x28/0x4c
 kasan_save_track+0x1c/0x34
 kasan_save_free_info+0x48/0x8c
 __kasan_slab_free+0x5c/0x84
 kfree+0x174/0x3e0
 driver_release+0x1c/0x7c
 kobject_put+0x178/0x47c
 driver_find+0x78/0xd4
 new_device_store+0x140/0x30c [pata_parport]
 bus_attr_store+0x5c/0x94
 sysfs_kf_write+0x1c4/0x25c
 ...

Fixes: 72f2b0b21850 ("drivers/block: Move PARIDE protocol modules to drivers/ata/pata_parport")
Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Closes: https://lore.kernel.org/lkml/20260728024015.2014674-1-shuangpeng.kernel@gmail.com/
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
 drivers/ata/pata_parport/pata_parport.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
index 40baeac594a9..34f09192a419 100644
--- a/drivers/ata/pata_parport/pata_parport.c
+++ b/drivers/ata/pata_parport/pata_parport.c
@@ -3,6 +3,7 @@
  * Copyright 2023 Ondrej Zary
  * based on paride.c by Grant R. Guenther <grant@torque.net>
  */
+#include <linux/cleanup.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/parport.h>
@@ -618,8 +619,9 @@ void pata_parport_unregister_driver(struct pi_protocol *pr)
 			break;
 	}
 	idr_remove(&protocols, id);
-	mutex_unlock(&pi_mutex);
 	driver_unregister(&pr->driver);
+	mutex_unlock(&pi_mutex);
+
 }
 EXPORT_SYMBOL_GPL(pata_parport_unregister_driver);
 
@@ -646,6 +648,7 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
 		port_wanted = -1;
 	}
 
+	guard(mutex)(&pi_mutex);
 	drv = driver_find(protocol, &pata_parport_bus_type);
 	if (!drv) {
 		if (strcmp(protocol, "auto")) {
@@ -656,15 +659,12 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
 	} else {
 		pr_wanted = container_of(drv, struct pi_protocol, driver);
 	}
-
-	mutex_lock(&pi_mutex);
 	/* walk all parports */
 	idr_for_each_entry(&parport_list, parport, port_num) {
 		if (port_num == port_wanted || port_wanted == -1) {
 			parport = parport_find_number(port_num);
 			if (!parport) {
 				pr_err("no such port %s\n", port);
-				mutex_unlock(&pi_mutex);
 				return -ENODEV;
 			}
 			/* walk all protocols */
@@ -677,7 +677,6 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
 			parport_put_port(parport);
 		}
 	}
-	mutex_unlock(&pi_mutex);
 	if (!ok)
 		return -ENODEV;
 
-- 
2.25.1

Re: [PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

Pre-existing issues:
- [High] Out-of-bounds array read due to lack of lower bound checking on user-provided `mode`.
- [High] Kernel soft lockup (infinite busy-wait) due to negative `delay` values provided via sysfs.
--

--- Patch [1]: [PATCH] ata: pata_parport: Fix use-after-free in new_device_store ---
commit 8244d117e0d1faf887a5bd4b26650cebdd4ecedb
Author: Pei Xiao <xiaopei01@kylinos.cn>

ata: pata_parport: Fix use-after-free in new_device_store

This commit fixes a use-after-free vulnerability in new_device_store() by
expanding the critical section protected by pi_mutex. It uses guard(mutex) to
ensure the driver pointer remains valid during lookup and subsequent uses,
preventing races with concurrent unregistration.

Closes: https://lore.kernel.org/lkml/20260728024015.2014674-1-shuangpeng.kernel@gmail.com/

> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
> index 40baeac594a9f..34f09192a4190 100644
> --- a/drivers/ata/pata_parport/pata_parport.c
> +++ b/drivers/ata/pata_parport/pata_parport.c

[ ... ]

> @@ -646,6 +648,7 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>  		port_wanted = -1;
>  	}
>  

[Severity: High]
This is a pre-existing issue, but does this sysfs input parsing properly
validate negative values for the mode parameter?

When new_device_store() uses sscanf() to read user input earlier in this
function, mode is parsed as a signed integer. If a user provides a negative
mode (e.g., -2), it bypasses the bounds check in pi_probe_mode(), which
uses a signed comparison:

drivers/ata/pata_parport/pata_parport.c:pi_probe_mode() {
    ...
    if (pi->mode >= max)
        return false;
    ...
}

This negative mode can then be passed to protocol drivers and used as an array
index, which could result in an out-of-bounds memory read. For example, in
bpck6_open():

drivers/ata/pata_parport/bpck6.c:bpck6_open() {
    ...
    i = mode_map[pi->mode] & 0x0C;
    ...
}

Could a lower bound check be added for the mode parameter?

[Severity: High]
This is also a pre-existing issue, but does this function properly handle
negative values for the delay parameter?

Similar to the mode parameter, delay is parsed via sscanf() as a signed
integer without lower bounds checking. The delay is heavily used in the
subsystem via the delay_p macro:

drivers/ata/pata_parport/pata_parport.h:
#define delay_p         (pi->delay ? udelay(pi->delay) : (void)0)

Since udelay() takes an unsigned long, passing a negative delay will
implicitly cast it to a massive positive number (e.g., ULONG_MAX - 1). This
will cause udelay() to busy-wait for an effectively infinite amount of time,
resulting in a CPU soft lockup.

Could the delay parameter be validated to prevent it from being negative?

> +	guard(mutex)(&pi_mutex);
>  	drv = driver_find(protocol, &pata_parport_bus_type);
>  	if (!drv) {
>  		if (strcmp(protocol, "auto")) {

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/7a9734be161cd051063ccc3bdeb377c55a83c4bf.1785327915.git.xiaopei01@kylinos.cn?part=1

Re: [PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[Niklas Cassel]

On Wed, Jul 29, 2026 at 08:27:53PM +0800, Pei Xiao wrote:

(snip)

> Fixes: 72f2b0b21850 ("drivers/block: Move PARIDE protocol modules to drivers/ata/pata_parport")

This does not look like the correct Fixes tag, since it is simply moving
files.

Not saying that it is super important to have a Fixes tag.

Without having looked, I'm guessing that there is a chance that this has
been racy/broken since the driver was introduced.


Kind regards,
Niklas

Re: [PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[Pei Xiao]

在 2026/7/29 21:10, Niklas Cassel 写道:
> On Wed, Jul 29, 2026 at 08:27:53PM +0800, Pei Xiao wrote:
> 
> (snip)
> 
>> Fixes: 72f2b0b21850 ("drivers/block: Move PARIDE protocol modules to drivers/ata/pata_parport")
> 
> This does not look like the correct Fixes tag, since it is simply moving
> files.
> 
Thank you for your reply. Perhaps I didn’t know how to use the --follow
option correctly, so the oldest commit I saw was the rename commit. But
now I’ve learned to use --follow, and I found the commit:

Fixes: 246a1c4c6b7f ("ata: pata_parport: add driver (PARIDE replacement)")
> Not saying that it is super important to have a Fixes tag.
> 
> Without having looked, I'm guessing that there is a chance that this has
> been racy/broken since the driver was introduced.
> 
> 
> Kind regards,
> Niklas

Re: [PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[Damien Le Moal]

On 7/29/26 21:27, Pei Xiao wrote:
> The function new_device_store() calls driver_find() without any
> protection against concurrent driver unregistration. This can lead
> to a use-after-free (UAF) when a driver is unloaded (via rmmod)
> in parallel with a new device addition via sysfs.
> 
> The race window exists because driver_find() returns a pointer to
> the driver's private data, but does not increase its reference
> count. The caller is responsible for ensuring the driver remains
> valid, but new_device_store() did not hold any lock or reference
> during the lookup and subsequent use.
> 
> Concurrently, pata_parport_unregister_driver() releases the
> pi_mutex before calling driver_unregister(), allowing new_device_store
> to proceed with a stale pointer after the driver has been freed.
> 
> Fix this by expanding the critical section protected by pi_mutex
> in both functions:
> 
> - In new_device_store(): acquire pi_mutex before calling driver_find(),
>   and keep it held until all uses of the found driver pointer are
>   completed.
> - In pata_parport_unregister_driver(): hold pi_mutex throughout the
>   entire unregistration process, including the driver_unregister()
>   call, so that no concurrent lookup can see a partially removed
>   driver.
> 
> Thread A (new_device_store)       | Thread B (pata_parport_unregister_driver)
>   driver_find("aten")             |
>                                   |   mutex_lock(&pi_mutex)
>                                   |   idr_remove(&protocols, id)
>                                   |   mutex_unlock(&pi_mutex)
>                                   |   driver_unregister(&pr->driver)
>                                   |   (frees driver_private)
>   /* continues using stale driv */|
>   -> UAF!                         |
> 
> Logs:
> BUG: KASAN: slab-use-after-free in driver_find+0xd0/0xd4
> Read of size 8 at addr ffffff9f970dc690 by task sh/4737
> Call trace:
>  show_stack+0x14/0x1c (C)
>  dump_stack_lvl+0x70/0x84
>  print_report+0xf4/0x5a4
>  kasan_report+0xa0/0xe4
>  __asan_report_load8_noabort+0x18/0x20
>  driver_find+0xd0/0xd4
>  new_device_store+0x140/0x30c [pata_parport]
>  bus_attr_store+0x5c/0x94
>  sysfs_kf_write+0x1c4/0x25c
>  ...
> 
> Allocated by task 4734:
>  kasan_save_stack+0x28/0x4c
>  kasan_save_track+0x1c/0x34
>  kasan_save_alloc_info+0x3c/0x4c
>  __kasan_kmalloc+0x98/0xac
>  __kmalloc_cache_noprof+0x158/0x3cc
>  bus_add_driver+0x70/0x4d8
>  driver_register+0xf0/0x3b0
>  pata_parport_register_driver+0xb8/0x1c4 [pata_parport]
>  0xffffffc07f5ce014
>  do_one_initcall+0xb8/0x36c
>  do_init_module+0x230/0x6d4
>  ...
> 
> Freed by task 4737:
>  kasan_save_stack+0x28/0x4c
>  kasan_save_track+0x1c/0x34
>  kasan_save_free_info+0x48/0x8c
>  __kasan_slab_free+0x5c/0x84
>  kfree+0x174/0x3e0
>  driver_release+0x1c/0x7c
>  kobject_put+0x178/0x47c
>  driver_find+0x78/0xd4
>  new_device_store+0x140/0x30c [pata_parport]
>  bus_attr_store+0x5c/0x94
>  sysfs_kf_write+0x1c4/0x25c
>  ...
> 
> Fixes: 72f2b0b21850 ("drivers/block: Move PARIDE protocol modules to drivers/ata/pata_parport")
> Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
> Closes: https://lore.kernel.org/lkml/20260728024015.2014674-1-shuangpeng.kernel@gmail.com/
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
> ---
>  drivers/ata/pata_parport/pata_parport.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
> index 40baeac594a9..34f09192a419 100644
> --- a/drivers/ata/pata_parport/pata_parport.c
> +++ b/drivers/ata/pata_parport/pata_parport.c
> @@ -3,6 +3,7 @@
>   * Copyright 2023 Ondrej Zary
>   * based on paride.c by Grant R. Guenther <grant@torque.net>
>   */
> +#include <linux/cleanup.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/parport.h>
> @@ -618,8 +619,9 @@ void pata_parport_unregister_driver(struct pi_protocol *pr)
>  			break;
>  	}
>  	idr_remove(&protocols, id);
> -	mutex_unlock(&pi_mutex);
>  	driver_unregister(&pr->driver);
> +	mutex_unlock(&pi_mutex);

Sashiko had a comment about this that I think is very valid: if rmmod is
executed with devices attached, what happens here?
This entire driver seems to be lacking reference counting on the
modules/drivers, so this all seems very fragile.

> +
>  }
>  EXPORT_SYMBOL_GPL(pata_parport_unregister_driver);
>  
> @@ -646,6 +648,7 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>  		port_wanted = -1;
>  	}
>  
> +	guard(mutex)(&pi_mutex);

Please no. We do not use these annotations anywhere in libata and I personally
consider anything that hides code a *bad* idea. So just move the mutex_lock()
call here and add the missing mutex_unlock() in the !drv case below.

>  	drv = driver_find(protocol, &pata_parport_bus_type);
>  	if (!drv) {
>  		if (strcmp(protocol, "auto")) {
> @@ -656,15 +659,12 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>  	} else {
>  		pr_wanted = container_of(drv, struct pi_protocol, driver);
>  	}
> -
> -	mutex_lock(&pi_mutex);
>  	/* walk all parports */
>  	idr_for_each_entry(&parport_list, parport, port_num) {
>  		if (port_num == port_wanted || port_wanted == -1) {
>  			parport = parport_find_number(port_num);
>  			if (!parport) {
>  				pr_err("no such port %s\n", port);
> -				mutex_unlock(&pi_mutex);
>  				return -ENODEV;
>  			}
>  			/* walk all protocols */
> @@ -677,7 +677,6 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>  			parport_put_port(parport);
>  		}
>  	}
> -	mutex_unlock(&pi_mutex);
>  	if (!ok)
>  		return -ENODEV;
>  


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH] ata: pata_parport: Fix use-after-free in new_device_store

[Pei Xiao]

在 2026/7/30 07:42, Damien Le Moal 写道:
> On 7/29/26 21:27, Pei Xiao wrote:
>> The function new_device_store() calls driver_find() without any
>> protection against concurrent driver unregistration. This can lead
>> to a use-after-free (UAF) when a driver is unloaded (via rmmod)
>> in parallel with a new device addition via sysfs.
>>
>> The race window exists because driver_find() returns a pointer to
>> the driver's private data, but does not increase its reference
>> count. The caller is responsible for ensuring the driver remains
>> valid, but new_device_store() did not hold any lock or reference
>> during the lookup and subsequent use.
>>
>> Concurrently, pata_parport_unregister_driver() releases the
>> pi_mutex before calling driver_unregister(), allowing new_device_store
>> to proceed with a stale pointer after the driver has been freed.
>>
>> Fix this by expanding the critical section protected by pi_mutex
>> in both functions:
>>
>> - In new_device_store(): acquire pi_mutex before calling driver_find(),
>>   and keep it held until all uses of the found driver pointer are
>>   completed.
>> - In pata_parport_unregister_driver(): hold pi_mutex throughout the
>>   entire unregistration process, including the driver_unregister()
>>   call, so that no concurrent lookup can see a partially removed
>>   driver.
>>
>> Thread A (new_device_store)       | Thread B (pata_parport_unregister_driver)
>>   driver_find("aten")             |
>>                                   |   mutex_lock(&pi_mutex)
>>                                   |   idr_remove(&protocols, id)
>>                                   |   mutex_unlock(&pi_mutex)
>>                                   |   driver_unregister(&pr->driver)
>>                                   |   (frees driver_private)
>>   /* continues using stale driv */|
>>   -> UAF!                         |
>>
>> Logs:
>> BUG: KASAN: slab-use-after-free in driver_find+0xd0/0xd4
>> Read of size 8 at addr ffffff9f970dc690 by task sh/4737
>> Call trace:
>>  show_stack+0x14/0x1c (C)
>>  dump_stack_lvl+0x70/0x84
>>  print_report+0xf4/0x5a4
>>  kasan_report+0xa0/0xe4
>>  __asan_report_load8_noabort+0x18/0x20
>>  driver_find+0xd0/0xd4
>>  new_device_store+0x140/0x30c [pata_parport]
>>  bus_attr_store+0x5c/0x94
>>  sysfs_kf_write+0x1c4/0x25c
>>  ...
>>
>> Allocated by task 4734:
>>  kasan_save_stack+0x28/0x4c
>>  kasan_save_track+0x1c/0x34
>>  kasan_save_alloc_info+0x3c/0x4c
>>  __kasan_kmalloc+0x98/0xac
>>  __kmalloc_cache_noprof+0x158/0x3cc
>>  bus_add_driver+0x70/0x4d8
>>  driver_register+0xf0/0x3b0
>>  pata_parport_register_driver+0xb8/0x1c4 [pata_parport]
>>  0xffffffc07f5ce014
>>  do_one_initcall+0xb8/0x36c
>>  do_init_module+0x230/0x6d4
>>  ...
>>
>> Freed by task 4737:
>>  kasan_save_stack+0x28/0x4c
>>  kasan_save_track+0x1c/0x34
>>  kasan_save_free_info+0x48/0x8c
>>  __kasan_slab_free+0x5c/0x84
>>  kfree+0x174/0x3e0
>>  driver_release+0x1c/0x7c
>>  kobject_put+0x178/0x47c
>>  driver_find+0x78/0xd4
>>  new_device_store+0x140/0x30c [pata_parport]
>>  bus_attr_store+0x5c/0x94
>>  sysfs_kf_write+0x1c4/0x25c
>>  ...
>>
>> Fixes: 72f2b0b21850 ("drivers/block: Move PARIDE protocol modules to drivers/ata/pata_parport")
>> Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
>> Closes: https://lore.kernel.org/lkml/20260728024015.2014674-1-shuangpeng.kernel@gmail.com/
>> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
>> ---
>>  drivers/ata/pata_parport/pata_parport.c | 9 ++++-----
>>  1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
>> index 40baeac594a9..34f09192a419 100644
>> --- a/drivers/ata/pata_parport/pata_parport.c
>> +++ b/drivers/ata/pata_parport/pata_parport.c
>> @@ -3,6 +3,7 @@
>>   * Copyright 2023 Ondrej Zary
>>   * based on paride.c by Grant R. Guenther <grant@torque.net>
>>   */
>> +#include <linux/cleanup.h>
>>  #include <linux/kernel.h>
>>  #include <linux/module.h>
>>  #include <linux/parport.h>
>> @@ -618,8 +619,9 @@ void pata_parport_unregister_driver(struct pi_protocol *pr)
>>  			break;
>>  	}
>>  	idr_remove(&protocols, id);
>> -	mutex_unlock(&pi_mutex);
>>  	driver_unregister(&pr->driver);
>> +	mutex_unlock(&pi_mutex);
> 
> Sashiko had a comment about this that I think is very valid: if rmmod is
> executed with devices attached, what happens here?
> This entire driver seems to be lacking reference counting on the
> modules/drivers, so this all seems very fragile.
Ok, I will check this issue then.
> 
>> +
>>  }
>>  EXPORT_SYMBOL_GPL(pata_parport_unregister_driver);
>>  
>> @@ -646,6 +648,7 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>>  		port_wanted = -1;
>>  	}
>>  
>> +	guard(mutex)(&pi_mutex);
> 
> Please no. We do not use these annotations anywhere in libata and I personally
> consider anything that hides code a *bad* idea. So just move the mutex_lock()
> call here and add the missing mutex_unlock() in the !drv case below.
Ok.

Thanks!
Pei.
> 
>>  	drv = driver_find(protocol, &pata_parport_bus_type);
>>  	if (!drv) {
>>  		if (strcmp(protocol, "auto")) {
>> @@ -656,15 +659,12 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>>  	} else {
>>  		pr_wanted = container_of(drv, struct pi_protocol, driver);
>>  	}
>> -
>> -	mutex_lock(&pi_mutex);
>>  	/* walk all parports */
>>  	idr_for_each_entry(&parport_list, parport, port_num) {
>>  		if (port_num == port_wanted || port_wanted == -1) {
>>  			parport = parport_find_number(port_num);
>>  			if (!parport) {
>>  				pr_err("no such port %s\n", port);
>> -				mutex_unlock(&pi_mutex);
>>  				return -ENODEV;
>>  			}
>>  			/* walk all protocols */
>> @@ -677,7 +677,6 @@ static ssize_t new_device_store(const struct bus_type *bus, const char *buf, siz
>>  			parport_put_port(parport);
>>  		}
>>  	}
>> -	mutex_unlock(&pi_mutex);
>>  	if (!ok)
>>  		return -ENODEV;
>>  
> 
>