[PATCH] of: overlay: fix memory leak in add_changeset_node()

[PATCH] of: overlay: fix memory leak in add_changeset_node()

[Zeng Heng]

In of_changeset_action(), we have called of_node_get() to increase
refcount of a node.

Therefore, when tchild (duplicated by __of_node_dup()) is done,
of_node_put() needs to call and release the device_node.

Otherwise, there are some memory leak reported about the node:

unreferenced object 0xffff88810cd1e800 (size 256):
  backtrace:
    kmalloc_trace
    __of_node_dup
    add_changeset_node (inlined)
    build_changeset_next_level

unreferenced object 0xffff888113721240 (size 16):
  backtrace:
    __kmalloc_node_track_caller
    kstrdup
    __of_node_dup
    add_changeset_node (inlined)
    build_changeset_next_level

unreferenced object 0xffff88810a38d400 (size 128):
  backtrace:
    kmalloc_trace
    __of_prop_dup
    add_changeset_property
    build_changeset_next_level

Fixes: 7518b5890d8a ("of/overlay: Introduce DT overlay support")
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
---
 drivers/of/overlay.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index bd8ff4df723d..a5189a0ec0a3 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -436,8 +436,10 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
 		of_node_set_flag(tchild, OF_OVERLAY);
 
 		ret = of_changeset_attach_node(&ovcs->cset, tchild);
-		if (ret)
+		if (ret) {
+			of_node_put(tchild);
 			return ret;
+		}
 
 		target_child.np = tchild;
 		target_child.in_livetree = false;
-- 
2.25.1

Re: [PATCH] of: overlay: fix memory leak in add_changeset_node()

[Frank Rowand]

On 11/18/22 04:53, Zeng Heng wrote:
> In of_changeset_action(), we have called of_node_get() to increase
> refcount of a node.
> 
> Therefore, when tchild (duplicated by __of_node_dup()) is done,
> of_node_put() needs to call and release the device_node.
> 
> Otherwise, there are some memory leak reported about the node:
> 
> unreferenced object 0xffff88810cd1e800 (size 256):
>   backtrace:
>     kmalloc_trace
>     __of_node_dup
>     add_changeset_node (inlined)
>     build_changeset_next_level
> 
> unreferenced object 0xffff888113721240 (size 16):
>   backtrace:
>     __kmalloc_node_track_caller
>     kstrdup
>     __of_node_dup
>     add_changeset_node (inlined)
>     build_changeset_next_level
> 
> unreferenced object 0xffff88810a38d400 (size 128):
>   backtrace:
>     kmalloc_trace
>     __of_prop_dup
>     add_changeset_property
>     build_changeset_next_level
> 
> Fixes: 7518b5890d8a ("of/overlay: Introduce DT overlay support")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> ---
>  drivers/of/overlay.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index bd8ff4df723d..a5189a0ec0a3 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -436,8 +436,10 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
>  		of_node_set_flag(tchild, OF_OVERLAY);
>  
>  		ret = of_changeset_attach_node(&ovcs->cset, tchild);
> -		if (ret)
> +		if (ret) {
> +			of_node_put(tchild);
>  			return ret;
> +		}

By visual inspection of the code (Linux 6.1-rc1), this does not appear to be
correct.  For the only case where of_changeset_action(),
called by of_changeset_attach_node(), returns an error, of_node_get() has not
yet occurred on tchild.

>  
>  		target_child.np = tchild;
>  		target_child.in_livetree = false;

For which version of Linux were the memory leaks detected?  Were any additional
patches applied?

-Frank

Re: [PATCH] of: overlay: fix memory leak in add_changeset_node()

[Zeng Heng]

On 2022/11/21 10:00, Frank Rowand wrote:
> On 11/18/22 04:53, Zeng Heng wrote:
>> In of_changeset_action(), we have called of_node_get() to increase
>> refcount of a node.
>>
>> Therefore, when tchild (duplicated by __of_node_dup()) is done,
>> of_node_put() needs to call and release the device_node.
>>
>> Otherwise, there are some memory leak reported about the node:
>>
>> unreferenced object 0xffff88810cd1e800 (size 256):
>>    backtrace:
>>      kmalloc_trace
>>      __of_node_dup
>>      add_changeset_node (inlined)
>>      build_changeset_next_level
>>
>> unreferenced object 0xffff888113721240 (size 16):
>>    backtrace:
>>      __kmalloc_node_track_caller
>>      kstrdup
>>      __of_node_dup
>>      add_changeset_node (inlined)
>>      build_changeset_next_level
>>
>> unreferenced object 0xffff88810a38d400 (size 128):
>>    backtrace:
>>      kmalloc_trace
>>      __of_prop_dup
>>      add_changeset_property
>>      build_changeset_next_level
>>
>> Fixes: 7518b5890d8a ("of/overlay: Introduce DT overlay support")
>> Signed-off-by: Zeng Heng<zengheng4@huawei.com>
>> ---
>>   drivers/of/overlay.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
>> index bd8ff4df723d..a5189a0ec0a3 100644
>> --- a/drivers/of/overlay.c
>> +++ b/drivers/of/overlay.c
>> @@ -436,8 +436,10 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
>>   		of_node_set_flag(tchild, OF_OVERLAY);
>>   
>>   		ret = of_changeset_attach_node(&ovcs->cset, tchild);
>> -		if (ret)
>> +		if (ret) {
>> +			of_node_put(tchild);
>>   			return ret;
>> +		}
> By visual inspection of the code (Linux 6.1-rc1), this does not appear to be
> correct.  For the only case where of_changeset_action(),
> called by of_changeset_attach_node(), returns an error, of_node_get() has not
> yet occurred on tchild.

The correct explanation should be like:

When of_changeset_attach_node() returns fail and tchild is over of life 
cycle which is duplicated by

__of_node_dup(), it needs to call of_node_put() to release tchild in 
error handle route.


The patch is fine, but feel sorry to apologize for the incorrect comment 
of the patch.

I would update the comment in the patch v2.


With Best Regards,

Zeng Heng

>>   
>>   		target_child.np = tchild;
>>   		target_child.in_livetree = false;
> For which version of Linux were the memory leaks detected?  Were any additional
> patches applied?
>
> -Frank

Re: [PATCH v2] of: overlay: fix memory leak in add_changeset_node()

[Zeng Heng]

+cc linux-kernel-mail-list


On 2022/11/21 11:53, Zeng Heng wrote:
> When of_changeset_attach_node() returns fail and tchild is
> over of life cycle which is duplicated by __of_node_dup(),
> it needs to call of_node_put() to release tchild in
> error handle route.
>
> Otherwise, there are some memory leak reported about the node:
>
> unreferenced object 0xffff88810cd1e800 (size 256):
>    backtrace:
>      kmalloc_trace
>      __of_node_dup
>      add_changeset_node (inlined)
>      build_changeset_next_level
>
> unreferenced object 0xffff888113721240 (size 16):
>    backtrace:
>      __kmalloc_node_track_caller
>      kstrdup
>      __of_node_dup
>      add_changeset_node (inlined)
>      build_changeset_next_level
>
> unreferenced object 0xffff88810a38d400 (size 128):
>    backtrace:
>      kmalloc_trace
>      __of_prop_dup
>      add_changeset_property
>      build_changeset_next_level
>
> Fixes: 0290c4ca2536 ("of: overlay: rename identifiers to more reflect what they do")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> ---
>   drivers/of/overlay.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index bd8ff4df723d..a5189a0ec0a3 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -436,8 +436,10 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
>   		of_node_set_flag(tchild, OF_OVERLAY);
>   
>   		ret = of_changeset_attach_node(&ovcs->cset, tchild);
> -		if (ret)
> +		if (ret) {
> +			of_node_put(tchild);
>   			return ret;
> +		}
>   
>   		target_child.np = tchild;
>   		target_child.in_livetree = false;

Re: [PATCH] of: overlay: fix memory leak in add_changeset_node()

[Frank Rowand]

On 11/18/22 04:53, Zeng Heng wrote:
> In of_changeset_action(), we have called of_node_get() to increase
> refcount of a node.
> 
> Therefore, when tchild (duplicated by __of_node_dup()) is done,
> of_node_put() needs to call and release the device_node.
> 
> Otherwise, there are some memory leak reported about the node:
> 
> unreferenced object 0xffff88810cd1e800 (size 256):
>   backtrace:
>     kmalloc_trace
>     __of_node_dup
>     add_changeset_node (inlined)
>     build_changeset_next_level
> 
> unreferenced object 0xffff888113721240 (size 16):
>   backtrace:
>     __kmalloc_node_track_caller
>     kstrdup
>     __of_node_dup
>     add_changeset_node (inlined)
>     build_changeset_next_level
> 
> unreferenced object 0xffff88810a38d400 (size 128):
>   backtrace:
>     kmalloc_trace
>     __of_prop_dup
>     add_changeset_property
>     build_changeset_next_level
> 
> Fixes: 7518b5890d8a ("of/overlay: Introduce DT overlay support")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> ---
>  drivers/of/overlay.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index bd8ff4df723d..a5189a0ec0a3 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -436,8 +436,10 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
>  		of_node_set_flag(tchild, OF_OVERLAY);
>  
>  		ret = of_changeset_attach_node(&ovcs->cset, tchild);
> -		if (ret)
> +		if (ret) {
> +			of_node_put(tchild);
>  			return ret;
> +		}
>  
>  		target_child.np = tchild;
>  		target_child.in_livetree = false;

Pending updated Fixes: tag (mentioned in a previous reply).

Reviewed-by: Frank Rowand <frowand.list@gmail.com>
Tested-by: Frank Rowand <frowand.list@gmail.com>

The testing was my normal testing, but did not replicate the triggered warning
to verify that this patch eliminated the warning.  I am depending upon Zeng having
verified the elimination of the warning.

-Frank