From 01c0b4265cc16bc1f43f475c5944c55c10d5768f Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Sat, 10 Mar 2018 23:04:23 +0100 Subject: [PATCH] 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: syzbot+4090700a4f13fccaf648@syzkaller.appspotmail.com Cc: Signed-off-by: Takashi Iwai --- sound/core/oss/pcm_oss.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index b044c0a5a674..02298c9c6020 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -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)