Re: [alsa-devel] [PATCH] OSS: keep index within bounds of midi_devs[]

At Mon, 16 Nov 2009 17:05:02 +0100, Roel Kluin wrote:

When the {orig,midi}_dev equals num_midis, that's one too large already.

Signed-off-by: Roel Kluin roel.kluin@gmail.com

In MIDIbuf_open() sound/oss/midibuf.c:166

    if (num_midis > MAX_MIDI_DEV)
    {
            printk(KERN_ERR "midi: Too many midi interfaces\n");
            num_midis = MAX_MIDI_DEV;
    }

num_midis is at most MAX_MIDI_DEV.

`git grep -n MAX_MIDI_DEV' and note that when the index equals num_midis this causes reads/writes outside array bounds for midi_devs, midi2synth, dev_conf and others (below check in patch).

The fix looks correct to me. Applied now.

Thanks.

Takashi

sound/oss/midi_synth.c | 2 +- sound/oss/mpu401.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/oss/midi_synth.c b/sound/oss/midi_synth.c index 9e45098..3bc7104 100644 --- a/sound/oss/midi_synth.c +++ b/sound/oss/midi_synth.c @@ -426,7 +426,7 @@ midi_synth_open(int dev, int mode) int err; struct midi_input_info *inc;

• if (orig_dev < 0 || orig_dev > num_midis || midi_devs[orig_dev] == NULL)

• if (orig_dev < 0 || orig_dev >= num_midis || midi_devs[orig_dev] == NULL) return -ENXIO;

  midi2synth[orig_dev] = dev;

diff --git a/sound/oss/mpu401.c b/sound/oss/mpu401.c index 734b8f9..0af9d24 100644 --- a/sound/oss/mpu401.c +++ b/sound/oss/mpu401.c @@ -770,7 +770,7 @@ static int mpu_synth_ioctl(int dev, unsigned int cmd, void __user *arg)

midi_dev = synth_devs[dev]->midi_dev;

• if (midi_dev < 0 || midi_dev > num_midis || midi_devs[midi_dev] == NULL)

• if (midi_dev < 0 || midi_dev >= num_midis || midi_devs[midi_dev] == NULL) return -ENXIO;

  devc = &dev_conf[midi_dev];