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SubjectRe: [PATCH] line6: add midibuf init failure handling in line6_init_midi()
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On 5/18/24 2:44 오전, Bjorn Helgaas wrote:
> On Fri, May 17, 2024 at 10:32:13AM +0200, Takashi Iwai wrote:
>> On Thu, 16 May 2024 19:47:38 +0200,
>> yskelg@gmail.com wrote:
>>>
>>> From: Yunseong Kim <yskelg@gmail.com>
>>>
>>> This patch fixes potential memory allocation failures in the
>>> line6_midibuf_init(). If either midibuf_in, midibuf_out allocation
>>> line6_midibuf_init call failed, the allocated memory for line6midi
>>> might have been leaked.
>>>
>>> This patch introduces an error handling label and uses goto to jump there
>>> in case of allocation failures. A kfree call is added to release any
>>> partially allocated memory before returning the error code.
>>>
>>> Signed-off-by: Yunseong Kim <yskelg@gmail.com>
>>
>> The allocated object is already freed by snd_line6_midi_free() that is
>> called via rawmidi private_free at its destruction. So your change
>> would lead to a double-free.
>
> I stand corrected, sorry that I missed that!
>
> That said, it seems unreasonably hard to verify this path to
> snd_line6_midi_free().
>
> Sorry for misleading you, Yunseong.

Thank you Bjorn for your detailed advice. I will take them to heart and
work on them in the future.

Warm Regards,
Yunseong Kim

>>> ---
>>> sound/usb/line6/midi.c | 9 +++++++--
>>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/sound/usb/line6/midi.c b/sound/usb/line6/midi.c
>>> index 0838632c788e..abcf58f46673 100644
>>> --- a/sound/usb/line6/midi.c
>>> +++ b/sound/usb/line6/midi.c
>>> @@ -283,13 +283,18 @@ int line6_init_midi(struct usb_line6 *line6)
>>>
>>> err = line6_midibuf_init(&line6midi->midibuf_in, MIDI_BUFFER_SIZE, 0);
>>> if (err < 0)
>>> - return err;
>>> + goto error;
>>>
>>> err = line6_midibuf_init(&line6midi->midibuf_out, MIDI_BUFFER_SIZE, 1);
>>> if (err < 0)
>>> - return err;
>>> + goto error;
>>>
>>> line6->line6midi = line6midi;
>>> return 0;
>>> +
>>> +error:
>>> + kfree(line6midi);
>>> + return err;
>>> +
>>> }
>>> EXPORT_SYMBOL_GPL(line6_init_midi);
>>> --
>>> 2.34.1
>>>

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