[v2] pps: fix warning in pps_register_cdev when register device fail

[PATCH v2] pps: fix warning in pps_register_cdev when register device fail

Posted by Wang Liang 5 months, 1 week ago

Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error
handling in __video_register_device()"), the release hook should be set
before device_register(). Otherwise, when device_register() return error
and put_device() try to callback the release function, the below warning
may happen.

  ------------[ cut here ]------------
  WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567
  Modules linked in:
  CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE
  RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567
  Call Trace:
   <TASK>
   kobject_cleanup+0x136/0x410 lib/kobject.c:689
   kobject_release lib/kobject.c:720 [inline]
   kref_put include/linux/kref.h:65 [inline]
   kobject_put+0xe9/0x130 lib/kobject.c:737
   put_device+0x24/0x30 drivers/base/core.c:3797
   pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402
   pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108
   pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57
   tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432
   tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563
   tiocsetd drivers/tty/tty_io.c:2429 [inline]
   tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728
   vfs_ioctl fs/ioctl.c:51 [inline]
   __do_sys_ioctl fs/ioctl.c:598 [inline]
   __se_sys_ioctl fs/ioctl.c:584 [inline]
   __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584
   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
   do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
   </TASK>

Before commit c79a39dc8d06 ("pps: Fix a use-after-free"),
pps_register_cdev() call device_create() to create pps->dev, which will
init dev->release to device_create_release(). Now the comment is outdated,
just remove it.

Thanks for the reminder from Calvin Owens, 'kfree_pps' should be removed
in pps_register_source() to avoid a double free in the failure case.

Link: https://lore.kernel.org/all/20250827065010.3208525-1-wangliang74@huawei.com/
Fixes: c79a39dc8d06 ("pps: Fix a use-after-free")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
---
v2: remove kfree_pps in pps_register_source().
---
 drivers/pps/kapi.c | 5 +----
 drivers/pps/pps.c  | 5 ++---
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index 92d1b62ea239..e9389876229e 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -109,16 +109,13 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
 	if (err < 0) {
 		pr_err("%s: unable to create char device\n",
 					info->name);
-		goto kfree_pps;
+		goto pps_register_source_exit;
 	}
 
 	dev_dbg(&pps->dev, "new PPS source %s\n", info->name);
 
 	return pps;
 
-kfree_pps:
-	kfree(pps);
-
 pps_register_source_exit:
 	pr_err("%s: unable to register source\n", info->name);
 
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 9463232af8d2..c6b8b6478276 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -374,6 +374,7 @@ int pps_register_cdev(struct pps_device *pps)
 			       pps->info.name);
 			err = -EBUSY;
 		}
+		kfree(pps);
 		goto out_unlock;
 	}
 	pps->id = err;
@@ -383,13 +384,11 @@ int pps_register_cdev(struct pps_device *pps)
 	pps->dev.devt = MKDEV(pps_major, pps->id);
 	dev_set_drvdata(&pps->dev, pps);
 	dev_set_name(&pps->dev, "pps%d", pps->id);
+	pps->dev.release = pps_device_destruct;
 	err = device_register(&pps->dev);
 	if (err)
 		goto free_idr;
 
-	/* Override the release function with our own */
-	pps->dev.release = pps_device_destruct;
-
 	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
 		 pps->id);
 
-- 
2.33.0

Re: [PATCH v2] pps: fix warning in pps_register_cdev when register device fail

Posted by Calvin Owens 5 months ago

On Saturday 08/30 at 15:50 +0800, Wang Liang wrote:
> Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error
> handling in __video_register_device()"), the release hook should be set
> before device_register(). Otherwise, when device_register() return error
> and put_device() try to callback the release function, the below warning
> may happen.
> 
>   ------------[ cut here ]------------
>   WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567
>   Modules linked in:
>   CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE
>   RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567
>   Call Trace:
>    <TASK>
>    kobject_cleanup+0x136/0x410 lib/kobject.c:689
>    kobject_release lib/kobject.c:720 [inline]
>    kref_put include/linux/kref.h:65 [inline]
>    kobject_put+0xe9/0x130 lib/kobject.c:737
>    put_device+0x24/0x30 drivers/base/core.c:3797
>    pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402
>    pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108
>    pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57
>    tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432
>    tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563
>    tiocsetd drivers/tty/tty_io.c:2429 [inline]
>    tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728
>    vfs_ioctl fs/ioctl.c:51 [inline]
>    __do_sys_ioctl fs/ioctl.c:598 [inline]
>    __se_sys_ioctl fs/ioctl.c:584 [inline]
>    __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584
>    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>    do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94
>    entry_SYSCALL_64_after_hwframe+0x76/0x7e
>    </TASK>
> 
> Before commit c79a39dc8d06 ("pps: Fix a use-after-free"),
> pps_register_cdev() call device_create() to create pps->dev, which will
> init dev->release to device_create_release(). Now the comment is outdated,
> just remove it.
> 
> Thanks for the reminder from Calvin Owens, 'kfree_pps' should be removed
> in pps_register_source() to avoid a double free in the failure case.

Looks good to me, thanks for cleaning this up :)

Reviewed-By: Calvin Owens <calvin@wbinvd.org>

> Link: https://lore.kernel.org/all/20250827065010.3208525-1-wangliang74@huawei.com/
> Fixes: c79a39dc8d06 ("pps: Fix a use-after-free")
> Signed-off-by: Wang Liang <wangliang74@huawei.com>
> ---
> v2: remove kfree_pps in pps_register_source().
> ---
>  drivers/pps/kapi.c | 5 +----
>  drivers/pps/pps.c  | 5 ++---
>  2 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
> index 92d1b62ea239..e9389876229e 100644
> --- a/drivers/pps/kapi.c
> +++ b/drivers/pps/kapi.c
> @@ -109,16 +109,13 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
>  	if (err < 0) {
>  		pr_err("%s: unable to create char device\n",
>  					info->name);
> -		goto kfree_pps;
> +		goto pps_register_source_exit;
>  	}
>  
>  	dev_dbg(&pps->dev, "new PPS source %s\n", info->name);
>  
>  	return pps;
>  
> -kfree_pps:
> -	kfree(pps);
> -
>  pps_register_source_exit:
>  	pr_err("%s: unable to register source\n", info->name);
>  
> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> index 9463232af8d2..c6b8b6478276 100644
> --- a/drivers/pps/pps.c
> +++ b/drivers/pps/pps.c
> @@ -374,6 +374,7 @@ int pps_register_cdev(struct pps_device *pps)
>  			       pps->info.name);
>  			err = -EBUSY;
>  		}
> +		kfree(pps);
>  		goto out_unlock;
>  	}
>  	pps->id = err;
> @@ -383,13 +384,11 @@ int pps_register_cdev(struct pps_device *pps)
>  	pps->dev.devt = MKDEV(pps_major, pps->id);
>  	dev_set_drvdata(&pps->dev, pps);
>  	dev_set_name(&pps->dev, "pps%d", pps->id);
> +	pps->dev.release = pps_device_destruct;
>  	err = device_register(&pps->dev);
>  	if (err)
>  		goto free_idr;
>  
> -	/* Override the release function with our own */
> -	pps->dev.release = pps_device_destruct;
> -
>  	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
>  		 pps->id);
>  
> -- 
> 2.33.0
>

Re: [PATCH v2] pps: fix warning in pps_register_cdev when register device fail

Posted by Rodolfo Giometti 5 months ago

On 04/09/25 06:08, Calvin Owens wrote:
> On Saturday 08/30 at 15:50 +0800, Wang Liang wrote:
>> Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error
>> handling in __video_register_device()"), the release hook should be set
>> before device_register(). Otherwise, when device_register() return error
>> and put_device() try to callback the release function, the below warning
>> may happen.
>>
>>    ------------[ cut here ]------------
>>    WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567
>>    Modules linked in:
>>    CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE
>>    RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567
>>    Call Trace:
>>     <TASK>
>>     kobject_cleanup+0x136/0x410 lib/kobject.c:689
>>     kobject_release lib/kobject.c:720 [inline]
>>     kref_put include/linux/kref.h:65 [inline]
>>     kobject_put+0xe9/0x130 lib/kobject.c:737
>>     put_device+0x24/0x30 drivers/base/core.c:3797
>>     pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402
>>     pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108
>>     pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57
>>     tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432
>>     tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563
>>     tiocsetd drivers/tty/tty_io.c:2429 [inline]
>>     tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728
>>     vfs_ioctl fs/ioctl.c:51 [inline]
>>     __do_sys_ioctl fs/ioctl.c:598 [inline]
>>     __se_sys_ioctl fs/ioctl.c:584 [inline]
>>     __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584
>>     do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>>     do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94
>>     entry_SYSCALL_64_after_hwframe+0x76/0x7e
>>     </TASK>
>>
>> Before commit c79a39dc8d06 ("pps: Fix a use-after-free"),
>> pps_register_cdev() call device_create() to create pps->dev, which will
>> init dev->release to device_create_release(). Now the comment is outdated,
>> just remove it.
>>
>> Thanks for the reminder from Calvin Owens, 'kfree_pps' should be removed
>> in pps_register_source() to avoid a double free in the failure case.
> 
> Looks good to me, thanks for cleaning this up :)
> 
> Reviewed-By: Calvin Owens <calvin@wbinvd.org>
> 
>> Link: https://lore.kernel.org/all/20250827065010.3208525-1-wangliang74@huawei.com/
>> Fixes: c79a39dc8d06 ("pps: Fix a use-after-free")
>> Signed-off-by: Wang Liang <wangliang74@huawei.com>
>> ---
>> v2: remove kfree_pps in pps_register_source().
>> ---
>>   drivers/pps/kapi.c | 5 +----
>>   drivers/pps/pps.c  | 5 ++---
>>   2 files changed, 3 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
>> index 92d1b62ea239..e9389876229e 100644
>> --- a/drivers/pps/kapi.c
>> +++ b/drivers/pps/kapi.c
>> @@ -109,16 +109,13 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
>>   	if (err < 0) {
>>   		pr_err("%s: unable to create char device\n",
>>   					info->name);
>> -		goto kfree_pps;
>> +		goto pps_register_source_exit;
>>   	}
>>   
>>   	dev_dbg(&pps->dev, "new PPS source %s\n", info->name);
>>   
>>   	return pps;
>>   
>> -kfree_pps:
>> -	kfree(pps);
>> -
>>   pps_register_source_exit:
>>   	pr_err("%s: unable to register source\n", info->name);
>>   
>> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
>> index 9463232af8d2..c6b8b6478276 100644
>> --- a/drivers/pps/pps.c
>> +++ b/drivers/pps/pps.c
>> @@ -374,6 +374,7 @@ int pps_register_cdev(struct pps_device *pps)
>>   			       pps->info.name);
>>   			err = -EBUSY;
>>   		}
>> +		kfree(pps);
>>   		goto out_unlock;
>>   	}
>>   	pps->id = err;
>> @@ -383,13 +384,11 @@ int pps_register_cdev(struct pps_device *pps)
>>   	pps->dev.devt = MKDEV(pps_major, pps->id);
>>   	dev_set_drvdata(&pps->dev, pps);
>>   	dev_set_name(&pps->dev, "pps%d", pps->id);
>> +	pps->dev.release = pps_device_destruct;
>>   	err = device_register(&pps->dev);
>>   	if (err)
>>   		goto free_idr;
>>   
>> -	/* Override the release function with our own */
>> -	pps->dev.release = pps_device_destruct;
>> -
>>   	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
>>   		 pps->id);
>>   
>> -- 
>> 2.33.0
>>

Acked-by: Rodolfo Giometti <giometti@enneenne.com>

-- 
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Linux Device Driver                          giometti@linux.it
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