Hi,
On 8/18/2017 11:30 AM, Manu Gautam wrote:
> Hi,
>
>
> On 8/15/2017 2:44 AM, Jerry Zhang wrote:
>> @@ -1197,14 +1200,21 @@ static void f_midi_free(struct usb_function *f)
>>
>> midi = func_to_midi(f);
>> opts = container_of(f->fi, struct f_midi_opts, func_inst);
> opts could be freed as well if f_midi_free_inst already happened. Say another
> user
> deleted midi instance before pcm_file was released.
This would be a regression (use-after-free) with the patch.
Do you plan to fix this as I see Felipe has already queued this for 4.14.
One simple solution could be to fail midi free_instance if pcm device
is in-use/open.
>> - kfree(midi->id);
>> mutex_lock(&opts->lock);
>> - kfifo_free(&midi->in_req_fifo);
>> - kfree(midi);
>> - --opts->refcnt;
>> + if (!--midi->free_ref) {
>> + kfree(midi->id);
>> + kfifo_free(&midi->in_req_fifo);
>> + kfree(midi);
>> + --opts->refcnt;
>> + }
>> mutex_unlock(&opts->lock);
>> }
>>
>> +static void f_midi_rmidi_free(struct snd_rawmidi *rmidi)
>> +{
>> + f_midi_free(rmidi->private_data);
>> +}
>> +
--
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