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

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Message-ID: <66f6f003-6488-295d-bae8-5e4c21db600d@arm.com>
Date:   Thu, 17 Aug 2023 15:46:29 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     James Clark <james.clark@....com>,
        Junhao He <hejunhao3@...wei.com>, mike.leach@...aro.org,
        leo.yan@...aro.org
Cc:     coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        jonathan.cameron@...wei.com, yangyicong@...wei.com,
        prime.zeng@...ilicon.com
Subject: Re: [PATCH 2/2] coresight: core: fix memory leak in dict->fwnode_list

On 17/08/2023 15:31, James Clark 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.
>>
>> Fixes: 0f5f9b6ba9e1 ("coresight: Use platform agnostic names")
>> Signed-off-by: Junhao He <hejunhao3@...wei.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;
>> +
> 
> Hi Junhao,
> 
> Changing the list allocator to a devm one fixes the issue without having
> to add the callback:
> 
>    -               list = krealloc_array(dict->fwnode_list,
>    +               list = devm_krealloc_array(dev, dict->fwnode_list,

Thats problematic. Please note that the list is "per module/driver" not 
per device. So, you cannot tie it to a single device. Please see my 
response in the thread.

Suzuki


> 
> The callback stands out a bit and would make someone reading it wonder
> why only that one is done that way but all other allocations in
> Coresight avoid it.
> 
> The nr_idx variable doesn't need to be zeroed because its backed by a
> static variable and is zeroed when the module is reloaded as far as I
> can see.
> 
> Thanks
> James
> 
>>   	idx = coresight_search_device_idx(dict, dev_fwnode(dev));
>>   	if (idx < 0) {
>>   		/* Make space for the new entry */