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Commit 01c0b426 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: pcm: Fix UAF in snd_pcm_oss_get_formats() 



snd_pcm_oss_get_formats() has an obvious use-after-free around
snd_mask_test() calls, as spotted by syzbot.  The passed format_mask
argument is a pointer to the hw_params object that is freed before the
loop.  What a surprise that it has been present since the original
code of decades ago...

Reported-by: default avatar <syzbot+4090700a4f13fccaf648@syzkaller.appspotmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a2ff19f7

sound/core/oss/pcm_oss.c

+6 −4
Original line number Diff line number Diff line
@@ -1762,10 +1762,9 @@ static int snd_pcm_oss_get_formats(struct snd_pcm_oss_file *pcm_oss_file) 
		return -ENOMEM;

	_snd_pcm_hw_params_any(params);

	err = snd_pcm_hw_refine(substream, params);

	format_mask = hw_param_mask_c(params, SNDRV_PCM_HW_PARAM_FORMAT);

	kfree(params);

	if (err < 0)

		return err;

		goto error;

	format_mask = hw_param_mask_c(params, SNDRV_PCM_HW_PARAM_FORMAT);

	for (fmt = 0; fmt < 32; ++fmt) {

		if (snd_mask_test(format_mask, fmt)) {

			int f = snd_pcm_oss_format_to(fmt);
@@ -1773,7 +1772,10 @@ static int snd_pcm_oss_get_formats(struct snd_pcm_oss_file *pcm_oss_file) 
				formats |= f;

		}

	}

	return formats;



 error:

	kfree(params);

	return err < 0 ? err : formats;

}



static int snd_pcm_oss_set_format(struct snd_pcm_oss_file *pcm_oss_file, int format)