[PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[Dawei Li]

Racing conflict could be:
task A                 task B
list_for_each_entry
strcmp(h->name))
                       list_for_each_entry
                       strcmp(h->name)
kzalloc                kzalloc
......                 .....
device_create          device_create
list_add
                       list_add

The root cause is that task B has no idea about the fact someone
else(A) has inserted heap with same name when it calls list_add,
so a potential collision occurs.

Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")
Signed-off-by: Dawei Li <set_pte_at@outlook.com>
---
v1: https://lore.kernel.org/all/TYCP286MB2323950197F60FC3473123B7CA349@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/
v1->v2: Narrow down locking scope, check the existence of heap before
insertion, as suggested by Andrew Davis.
v2->v3: Remove double checking.
v3->v4: Minor coding style and patch formatting adjustment.
---
 drivers/dma-buf/dma-heap.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index 8f5848aa144f..59d158873f4c 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
 		return ERR_PTR(-EINVAL);
 	}
 
-	/* check the name is unique */
-	mutex_lock(&heap_list_lock);
-	list_for_each_entry(h, &heap_list, list) {
-		if (!strcmp(h->name, exp_info->name)) {
-			mutex_unlock(&heap_list_lock);
-			pr_err("dma_heap: Already registered heap named %s\n",
-			       exp_info->name);
-			return ERR_PTR(-EINVAL);
-		}
-	}
-	mutex_unlock(&heap_list_lock);
-
 	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
 	if (!heap)
 		return ERR_PTR(-ENOMEM);
@@ -283,13 +271,27 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
 		err_ret = ERR_CAST(dev_ret);
 		goto err2;
 	}
-	/* Add heap to the list */
+
 	mutex_lock(&heap_list_lock);
+	/* check the name is unique */
+	list_for_each_entry(h, &heap_list, list) {
+		if (!strcmp(h->name, exp_info->name)) {
+			mutex_unlock(&heap_list_lock);
+			pr_err("dma_heap: Already registered heap named %s\n",
+			       exp_info->name);
+			err_ret = ERR_PTR(-EINVAL);
+			goto err3;
+		}
+	}
+
+	/* Add heap to the list */
 	list_add(&heap->list, &heap_list);
 	mutex_unlock(&heap_list_lock);
 
 	return heap;
 
+err3:
+	device_destroy(dma_heap_class, heap->heap_devt);
 err2:
 	cdev_del(&heap->heap_cdev);
 err1:
-- 
2.25.1

Re: [PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[Andrew Davis]

On 11/4/22 11:05 AM, Dawei Li wrote:
> Racing conflict could be:
> task A                 task B
> list_for_each_entry
> strcmp(h->name))
>                         list_for_each_entry
>                         strcmp(h->name)
> kzalloc                kzalloc
> ......                 .....
> device_create          device_create
> list_add
>                         list_add
> 
> The root cause is that task B has no idea about the fact someone
> else(A) has inserted heap with same name when it calls list_add,
> so a potential collision occurs.
> 
> Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")
> Signed-off-by: Dawei Li <set_pte_at@outlook.com>

LGTM, Thanks,

Acked-by: Andrew Davis <afd@ti.com>

> ---
> v1: https://lore.kernel.org/all/TYCP286MB2323950197F60FC3473123B7CA349@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/
> v1->v2: Narrow down locking scope, check the existence of heap before
> insertion, as suggested by Andrew Davis.
> v2->v3: Remove double checking.
> v3->v4: Minor coding style and patch formatting adjustment.
> ---
>   drivers/dma-buf/dma-heap.c | 28 +++++++++++++++-------------
>   1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> index 8f5848aa144f..59d158873f4c 100644
> --- a/drivers/dma-buf/dma-heap.c
> +++ b/drivers/dma-buf/dma-heap.c
> @@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>   		return ERR_PTR(-EINVAL);
>   	}
>   
> -	/* check the name is unique */
> -	mutex_lock(&heap_list_lock);
> -	list_for_each_entry(h, &heap_list, list) {
> -		if (!strcmp(h->name, exp_info->name)) {
> -			mutex_unlock(&heap_list_lock);
> -			pr_err("dma_heap: Already registered heap named %s\n",
> -			       exp_info->name);
> -			return ERR_PTR(-EINVAL);
> -		}
> -	}
> -	mutex_unlock(&heap_list_lock);
> -
>   	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
>   	if (!heap)
>   		return ERR_PTR(-ENOMEM);
> @@ -283,13 +271,27 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>   		err_ret = ERR_CAST(dev_ret);
>   		goto err2;
>   	}
> -	/* Add heap to the list */
> +
>   	mutex_lock(&heap_list_lock);
> +	/* check the name is unique */
> +	list_for_each_entry(h, &heap_list, list) {
> +		if (!strcmp(h->name, exp_info->name)) {
> +			mutex_unlock(&heap_list_lock);
> +			pr_err("dma_heap: Already registered heap named %s\n",
> +			       exp_info->name);
> +			err_ret = ERR_PTR(-EINVAL);
> +			goto err3;
> +		}
> +	}
> +
> +	/* Add heap to the list */
>   	list_add(&heap->list, &heap_list);
>   	mutex_unlock(&heap_list_lock);
>   
>   	return heap;
>   
> +err3:
> +	device_destroy(dma_heap_class, heap->heap_devt);
>   err2:
>   	cdev_del(&heap->heap_cdev);
>   err1:

Re: [PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[Dawei Li]

On Sat, Nov 05, 2022 at 12:05:36AM +0800, Dawei Li wrote:

Hi Christian,
May I have your opinion on this change?

Thanks,
Dawei

> Racing conflict could be:
> task A                 task B
> list_for_each_entry
> strcmp(h->name))
>                        list_for_each_entry
>                        strcmp(h->name)
> kzalloc                kzalloc
> ......                 .....
> device_create          device_create
> list_add
>                        list_add
> 
> The root cause is that task B has no idea about the fact someone
> else(A) has inserted heap with same name when it calls list_add,
> so a potential collision occurs.
> 
> Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")
> Signed-off-by: Dawei Li <set_pte_at@outlook.com>
> ---
> v1: https://lore.kernel.org/all/TYCP286MB2323950197F60FC3473123B7CA349@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/
> v1->v2: Narrow down locking scope, check the existence of heap before
> insertion, as suggested by Andrew Davis.
> v2->v3: Remove double checking.
> v3->v4: Minor coding style and patch formatting adjustment.
> ---
>  drivers/dma-buf/dma-heap.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> index 8f5848aa144f..59d158873f4c 100644
> --- a/drivers/dma-buf/dma-heap.c
> +++ b/drivers/dma-buf/dma-heap.c
> @@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> -	/* check the name is unique */
> -	mutex_lock(&heap_list_lock);
> -	list_for_each_entry(h, &heap_list, list) {
> -		if (!strcmp(h->name, exp_info->name)) {
> -			mutex_unlock(&heap_list_lock);
> -			pr_err("dma_heap: Already registered heap named %s\n",
> -			       exp_info->name);
> -			return ERR_PTR(-EINVAL);
> -		}
> -	}
> -	mutex_unlock(&heap_list_lock);
> -
>  	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
>  	if (!heap)
>  		return ERR_PTR(-ENOMEM);
> @@ -283,13 +271,27 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>  		err_ret = ERR_CAST(dev_ret);
>  		goto err2;
>  	}
> -	/* Add heap to the list */
> +
>  	mutex_lock(&heap_list_lock);
> +	/* check the name is unique */
> +	list_for_each_entry(h, &heap_list, list) {
> +		if (!strcmp(h->name, exp_info->name)) {
> +			mutex_unlock(&heap_list_lock);
> +			pr_err("dma_heap: Already registered heap named %s\n",
> +			       exp_info->name);
> +			err_ret = ERR_PTR(-EINVAL);
> +			goto err3;
> +		}
> +	}
> +
> +	/* Add heap to the list */
>  	list_add(&heap->list, &heap_list);
>  	mutex_unlock(&heap_list_lock);
>  
>  	return heap;
>  
> +err3:
> +	device_destroy(dma_heap_class, heap->heap_devt);
>  err2:
>  	cdev_del(&heap->heap_cdev);
>  err1:
> -- 
> 2.25.1
> 

Re: [PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[Christian König]

Hi Dawei,

from the technical description, coding style etc.. it looks clean to me, 
but I'm the completely wrong person to ask for a background check.

I have a high level understanding of how dma-heaps work, but not a 
single line of this code is from me.

Feel free to add my Acked-by, but Laura, John and others do you have any 
opinion?

Regards,
Christian.

Am 21.11.22 um 16:28 schrieb Dawei Li:
> On Sat, Nov 05, 2022 at 12:05:36AM +0800, Dawei Li wrote:
>
> Hi Christian,
> May I have your opinion on this change?
>
> Thanks,
> Dawei
>
>> Racing conflict could be:
>> task A                 task B
>> list_for_each_entry
>> strcmp(h->name))
>>                         list_for_each_entry
>>                         strcmp(h->name)
>> kzalloc                kzalloc
>> ......                 .....
>> device_create          device_create
>> list_add
>>                         list_add
>>
>> The root cause is that task B has no idea about the fact someone
>> else(A) has inserted heap with same name when it calls list_add,
>> so a potential collision occurs.
>>
>> Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")
>> Signed-off-by: Dawei Li <set_pte_at@outlook.com>
>> ---
>> v1: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2FTYCP286MB2323950197F60FC3473123B7CA349%40TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM%2F&amp;data=05%7C01%7Cchristian.koenig%40amd.com%7C1989f31257fc458a27c508dacbd5078e%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638046413707443203%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=OWPUPrIHGnzwXyQE4WlIthThwSuSK2y3Eq2Wq5zAzbo%3D&amp;reserved=0
>> v1->v2: Narrow down locking scope, check the existence of heap before
>> insertion, as suggested by Andrew Davis.
>> v2->v3: Remove double checking.
>> v3->v4: Minor coding style and patch formatting adjustment.
>> ---
>>   drivers/dma-buf/dma-heap.c | 28 +++++++++++++++-------------
>>   1 file changed, 15 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
>> index 8f5848aa144f..59d158873f4c 100644
>> --- a/drivers/dma-buf/dma-heap.c
>> +++ b/drivers/dma-buf/dma-heap.c
>> @@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>>   		return ERR_PTR(-EINVAL);
>>   	}
>>   
>> -	/* check the name is unique */
>> -	mutex_lock(&heap_list_lock);
>> -	list_for_each_entry(h, &heap_list, list) {
>> -		if (!strcmp(h->name, exp_info->name)) {
>> -			mutex_unlock(&heap_list_lock);
>> -			pr_err("dma_heap: Already registered heap named %s\n",
>> -			       exp_info->name);
>> -			return ERR_PTR(-EINVAL);
>> -		}
>> -	}
>> -	mutex_unlock(&heap_list_lock);
>> -
>>   	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
>>   	if (!heap)
>>   		return ERR_PTR(-ENOMEM);
>> @@ -283,13 +271,27 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>>   		err_ret = ERR_CAST(dev_ret);
>>   		goto err2;
>>   	}
>> -	/* Add heap to the list */
>> +
>>   	mutex_lock(&heap_list_lock);
>> +	/* check the name is unique */
>> +	list_for_each_entry(h, &heap_list, list) {
>> +		if (!strcmp(h->name, exp_info->name)) {
>> +			mutex_unlock(&heap_list_lock);
>> +			pr_err("dma_heap: Already registered heap named %s\n",
>> +			       exp_info->name);
>> +			err_ret = ERR_PTR(-EINVAL);
>> +			goto err3;
>> +		}
>> +	}
>> +
>> +	/* Add heap to the list */
>>   	list_add(&heap->list, &heap_list);
>>   	mutex_unlock(&heap_list_lock);
>>   
>>   	return heap;
>>   
>> +err3:
>> +	device_destroy(dma_heap_class, heap->heap_devt);
>>   err2:
>>   	cdev_del(&heap->heap_cdev);
>>   err1:
>> -- 
>> 2.25.1
>>

Re: [PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[Sumit Semwal]

Hi Dawei Li,

On Mon, 21 Nov 2022 at 23:53, Christian König <christian.koenig@amd.com> wrote:
>
> Hi Dawei,
>
> from the technical description, coding style etc.. it looks clean to me,
> but I'm the completely wrong person to ask for a background check.
>
> I have a high level understanding of how dma-heaps work, but not a
> single line of this code is from me.
>
> Feel free to add my Acked-by, but Laura, John and others do you have any
> opinion?
>
> Regards,
> Christian.
>
> Am 21.11.22 um 16:28 schrieb Dawei Li:
> > On Sat, Nov 05, 2022 at 12:05:36AM +0800, Dawei Li wrote:
> >
> > Hi Christian,
> > May I have your opinion on this change?
> >
> > Thanks,
> > Dawei
> >
> >> Racing conflict could be:
> >> task A                 task B
> >> list_for_each_entry
> >> strcmp(h->name))
> >>                         list_for_each_entry
> >>                         strcmp(h->name)
> >> kzalloc                kzalloc
> >> ......                 .....
> >> device_create          device_create
> >> list_add
> >>                         list_add
> >>
> >> The root cause is that task B has no idea about the fact someone
> >> else(A) has inserted heap with same name when it calls list_add,
> >> so a potential collision occurs.
> >>
> >> Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")
> >> Signed-off-by: Dawei Li <set_pte_at@outlook.com>

Looks good to me as well. I will apply it over on drm-misc.

Best,
Sumit.
> >> ---
> >> v1: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2FTYCP286MB2323950197F60FC3473123B7CA349%40TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM%2F&amp;data=05%7C01%7Cchristian.koenig%40amd.com%7C1989f31257fc458a27c508dacbd5078e%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638046413707443203%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=OWPUPrIHGnzwXyQE4WlIthThwSuSK2y3Eq2Wq5zAzbo%3D&amp;reserved=0
> >> v1->v2: Narrow down locking scope, check the existence of heap before
> >> insertion, as suggested by Andrew Davis.
> >> v2->v3: Remove double checking.
> >> v3->v4: Minor coding style and patch formatting adjustment.
> >> ---
> >>   drivers/dma-buf/dma-heap.c | 28 +++++++++++++++-------------
> >>   1 file changed, 15 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> >> index 8f5848aa144f..59d158873f4c 100644
> >> --- a/drivers/dma-buf/dma-heap.c
> >> +++ b/drivers/dma-buf/dma-heap.c
> >> @@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
> >>              return ERR_PTR(-EINVAL);
> >>      }
> >>
> >> -    /* check the name is unique */
> >> -    mutex_lock(&heap_list_lock);
> >> -    list_for_each_entry(h, &heap_list, list) {
> >> -            if (!strcmp(h->name, exp_info->name)) {
> >> -                    mutex_unlock(&heap_list_lock);
> >> -                    pr_err("dma_heap: Already registered heap named %s\n",
> >> -                           exp_info->name);
> >> -                    return ERR_PTR(-EINVAL);
> >> -            }
> >> -    }
> >> -    mutex_unlock(&heap_list_lock);
> >> -
> >>      heap = kzalloc(sizeof(*heap), GFP_KERNEL);
> >>      if (!heap)
> >>              return ERR_PTR(-ENOMEM);
> >> @@ -283,13 +271,27 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
> >>              err_ret = ERR_CAST(dev_ret);
> >>              goto err2;
> >>      }
> >> -    /* Add heap to the list */
> >> +
> >>      mutex_lock(&heap_list_lock);
> >> +    /* check the name is unique */
> >> +    list_for_each_entry(h, &heap_list, list) {
> >> +            if (!strcmp(h->name, exp_info->name)) {
> >> +                    mutex_unlock(&heap_list_lock);
> >> +                    pr_err("dma_heap: Already registered heap named %s\n",
> >> +                           exp_info->name);
> >> +                    err_ret = ERR_PTR(-EINVAL);
> >> +                    goto err3;
> >> +            }
> >> +    }
> >> +
> >> +    /* Add heap to the list */
> >>      list_add(&heap->list, &heap_list);
> >>      mutex_unlock(&heap_list_lock);
> >>
> >>      return heap;
> >>
> >> +err3:
> >> +    device_destroy(dma_heap_class, heap->heap_devt);
> >>   err2:
> >>      cdev_del(&heap->heap_cdev);
> >>   err1:
> >> --
> >> 2.25.1
> >>
>


-- 
Thanks and regards,

Sumit Semwal (he / him)
Tech Lead - LCG, Vertical Technologies
Linaro.org │ Open source software for ARM SoCs

Re: [PATCH v4] dma-buf: fix racing conflict of dma_heap_add()

[John Stultz]

On Mon, Nov 21, 2022 at 10:24 AM Christian König
<christian.koenig@amd.com> wrote:
>
> Hi Dawei,
>
> from the technical description, coding style etc.. it looks clean to me,
> but I'm the completely wrong person to ask for a background check.
>
> I have a high level understanding of how dma-heaps work, but not a
> single line of this code is from me.
>
> Feel free to add my Acked-by, but Laura, John and others do you have any
> opinion?

No objection from me.
Thanks Dawei for submitting this improvement!

Acked-by: John Stultz <jstultz@google.com>

thanks
-john