Re: [alsa-devel] [patch v3] ALSA: rawmidi: fix the get next midi device ioctl

At Thu, 9 Sep 2010 00:11:41 +0200, Dan Carpenter wrote:

If we pass in a device which is higher than SNDRV_RAWMIDI_DEVICES then the "next device" should be -1. This function just returns device + 1.

But the main thing is that "device + 1" can lead to a (harmless) integer overflow and that annoys static analysis tools.

Signed-off-by: Dan Carpenter error27@gmail.com

V2: In the first version I made negative values return -EINVAL V3: We shouldn't return -EINVAL for numbers which are too large but just set the next device to -1.

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c index eb68326..df67605 100644 --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -829,6 +829,8 @@ static int snd_rawmidi_control_ioctl(struct snd_card *card, if (get_user(device, (int __user *)argp)) return -EFAULT;

• if (device > SNDRV_RAWMIDI_DEVICES) /* next device is -1 */
  

• 	device = SNDRV_RAWMIDI_DEVICES;
  

  mutex_lock(&register_mutex); device = device < 0 ? 0 : device + 1; while (device < SNDRV_RAWMIDI_DEVICES) {

We still need to cover the case device == SNDRV_RAWMIDI_DEVICES. Also, device is incremented, so it has to be SNDRV_RAWMIDI_DEVICE - 1. i.e.

• if (device >= SNDRV_RAWMIDI_DEVICES) /* next device is -1 */
  

• 	device = SNDRV_RAWMIDI_DEVICES - 1;
  

I applied the fixed patch now.

thanks,

Takashi