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

[Jie Gan <jie.gan@oss.qualcomm.com>]

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.

> 
> 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

> 
> 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>
>