Re: [PATCH] coresight: fix resource leaks on path build failure

[James Clark <james.clark@linaro.org>]

On 20/05/2026 2:55 am, Jie Gan wrote:
> 
> 
> On 5/19/2026 9:57 PM, James Clark wrote:
>>
>>
>> On 13/05/2026 2:32 am, Jie Gan wrote:
>>> Two related leaks when _coresight_build_path() encounters an error after
>>> coresight_grab_device() has already incremented the pm_runtime, module,
>>> and device references for a node:
>>>
>>> 1. In _coresight_build_path(), if kzalloc_obj() for the path node fails
>>>     after coresight_grab_device() succeeds, coresight_drop_device() was
>>>     never called, permanently leaking all three references.
>>>
>>> 2. In coresight_build_path(), on failure the partial path was freed with
>>>     kfree(path) instead of coresight_release_path(path).  kfree() only
>>>     frees the coresight_path struct itself; it does not iterate 
>>> path_list
>>>     to call coresight_drop_device() and kfree() for each coresight_node
>>>     already added by deeper recursive calls, leaking both the 
>>> pm_runtime,
>>>     module, and device references and the node memory for every element
>>>     on the partial path.
>>>
>>> Fix both by adding coresight_drop_device() in the OOM unwind of
>>> _coresight_build_path(), and replacing kfree(path) with
>>> coresight_release_path(path) in coresight_build_path().
>>>
>>> Fixes: 32b0707a4182 ("coresight: Add try_get_module() in 
>>> coresight_grab_device()")
>>> Fixes: b3e94405941e ("coresight: associating path with session rather 
>>> than tracer")
>>> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
>>> ---
>>>   drivers/hwtracing/coresight/coresight-core.c | 6 ++++--
>>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/ 
>>> hwtracing/coresight/coresight-core.c
>>> index 46f247f73cf6..c1354ea8e11d 100644
>>> --- a/drivers/hwtracing/coresight/coresight-core.c
>>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>>> @@ -825,8 +825,10 @@ static int _coresight_build_path(struct 
>>> coresight_device *csdev,
>>>           return ret;
>>>       node = kzalloc_obj(struct coresight_node);
>>> -    if (!node)
>>> +    if (!node) {
>>> +        coresight_drop_device(csdev);
>>>           return -ENOMEM;
>>> +    }
>>>       node->csdev = csdev;
>>>       list_add(&node->link, &path->path_list);
>>> @@ -851,7 +853,7 @@ struct coresight_path 
>>> *coresight_build_path(struct coresight_device *source,
>>>       rc = _coresight_build_path(source, source, sink, path);
>>>       if (rc) {
>>> -        kfree(path);
>>> +        coresight_release_path(path);
>>>           return ERR_PTR(rc);
>>>       }
>>>
>>> ---
>>> base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
>>> change-id: 20260513-fix-memory-leak-issue-034b4a45265e
>>>
>>> Best regards,
>>
>> Looks good to me, but sashiko is complaining: https://sashiko.dev/#/ 
>> patchset/20260513-fix-memory-leak-issue- 
>> v1-1-49822d7bc7d4%40oss.qualcomm.com
>>
>> I'm trying to understand why it's saying that, but I think the 
>> scenario is that if there are multiple correct paths to a sink, when 
>> one path partially fails and a second path succeeds you could get a 
>> path_list with some garbage entries in it.
> 
> I think the coresight_release_path is added to address this situation.
> We suffered the path partially failure, and we need release all nodes 
> already added to the path.
> 

It wouldn't call coresight_release_path() in this case though. If one 
path ends up building to success but a parallel path partially failed 
then _coresight_build_path() still returns success. During the search it 
would have still added the nodes from the partially failed path to the 
path_list. This is only an issue if there are multiple correct paths.

>>
>> That's kind of a different and existing issue to the one you've fixed, 
>> and assumes that multiple paths to one sink are possible, which I'm 
>> not sure is supported?
> 
> Each path is unique. We only deal with the issue path for balancing the 
> reference count.
> 
> Thanks,
> Jie
> 

I'm not exactly sure what you mean by unique, but the same source and 
sink could potentially be connected through two different sets of links.

>>
>> It might be as easy as breaking the loop early for any return value 
>> other than -ENODEV, but I'll leave it to you to decide whether to do 
>> that here or not.
>>
>> Reviewed-by: James Clark <james.clark@linaro.org>
>>
>