Re: [PATCH 2/2] coresight: core: fix memory leak in dict->fwnode_list

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 17/08/2023 15:39, Suzuki K Poulose wrote:
> On 17/08/2023 09:59, Junhao He wrote:
>> There are memory leaks reported by kmemleak:
>> ...
>> unreferenced object 0xffff2020103c3200 (size 256):
>>    comm "insmod", pid 4476, jiffies 4294978252 (age 50072.536s)
>>    hex dump (first 32 bytes):
>>      10 60 40 06 28 20 ff ff 10 c0 59 06 20 20 ff ff  .`@.( ....Y.  ..
>>      10 e0 47 06 28 20 ff ff 10 00 49 06 28 20 ff ff  ..G.( ....I.( ..
>>    backtrace:
>>      [<0000000034ec4724>] __kmem_cache_alloc_node+0x2f8/0x348
>>      [<0000000057fbc15d>] __kmalloc_node_track_caller+0x5c/0x110
>>      [<00000055d5e34b>] krealloc+0x8c/0x178
>>      [<00000000a4635beb>] coresight_alloc_device_name+0x128/0x188 
>> [coresight]
>>      [<00000000a92ddfee>] funnel_cs_ops+0x10/0xfffffffffffedaa0 
>> [coresight_funnel]
>>      [<00000000449e20f8>] dynamic_funnel_ids+0x80/0xfffffffffffed840 
>> [coresight_funnel]
>> ...
>>
>> when remove driver, the golab variables defined by the macro
>> DEFINE_CORESIGHT_DEVLIST will be released, dict->nr_idx and
>> dict->fwnode_list are cleared to 0. The lifetime of the golab
>> variable has ended. So the buffer pointer is lost.
>>
>> Use the callback of devm_add_action_or_reset() to free memory.
> 
> Thanks for the report. But please see below:
> 
>>
>> Fixes: 0f5f9b6ba9e1 ("coresight: Use platform agnostic names")
>> Signed-off-by: Junhao He <hejunhao3@huawei.com>
>> ---
>>   drivers/hwtracing/coresight/coresight-core.c | 20 +++++++++++++++++++-
>>   1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c 
>> b/drivers/hwtracing/coresight/coresight-core.c
>> index 9fabe00a40d6..6849faad697d 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -1756,6 +1756,20 @@ bool coresight_loses_context_with_cpu(struct 
>> device *dev)
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_loses_context_with_cpu);
>> +void coresight_release_dev_list(void *data)
>> +{
>> +    struct coresight_dev_list *dict = data;
>> +
>> +    mutex_lock(&coresight_mutex);
>> +
>> +    if (dict->nr_idx) {
>> +        kfree(dict->fwnode_list);
>> +        dict->nr_idx = 0;
>> +    }
>> +
>> +    mutex_unlock(&coresight_mutex);
>> +}
>> +
>>   /*
>>    * coresight_alloc_device_name - Get an index for a given device in the
>>    * device index list specific to a driver. An index is allocated for a
>> @@ -1766,12 +1780,16 @@ 
>> EXPORT_SYMBOL_GPL(coresight_loses_context_with_cpu);
>>   char *coresight_alloc_device_name(struct coresight_dev_list *dict,
>>                     struct device *dev)
>>   {
>> -    int idx;
>> +    int idx, ret;
>>       char *name = NULL;
>>       struct fwnode_handle **list;
>>       mutex_lock(&coresight_mutex);
>> +    ret = devm_add_action_or_reset(dev, coresight_release_dev_list, 
>> dict);
>> +    if (ret)
>> +        goto done;
> 
> This looks wrong. The devlist should be only released on the "driver" 
> unload, not on every device release. The list retains the fwnode to
> assign the same name for a device, if it is re-probed (e.g., due to
> -EPROBE_DEFER error).

The best way is to free it on module_unload and unfortunately we would
need to do it from all modules using the DEVLIST.

Suzuki


> 
> Suzuki
> 


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