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

[Suzuki K Poulose]

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@xxxxxxxxxx>
> > ---
> >   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 */