This is a note to let you know that I've just added the patch titled
ALSA: pcm: Fix UAF in snd_pcm_oss_get_formats()
to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: alsa-pcm-fix-uaf-in-snd_pcm_oss_get_formats.patch and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 01c0b4265cc16bc1f43f475c5944c55c10d5768f Mon Sep 17 00:00:00 2001
From: Takashi Iwai tiwai@suse.de Date: Sat, 10 Mar 2018 23:04:23 +0100 Subject: ALSA: pcm: Fix UAF in snd_pcm_oss_get_formats()
From: Takashi Iwai tiwai@suse.de
commit 01c0b4265cc16bc1f43f475c5944c55c10d5768f upstream.
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: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- sound/core/oss/pcm_oss.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1815,10 +1815,9 @@ static int snd_pcm_oss_get_formats(struc return -ENOMEM; _snd_pcm_hw_params_any(params); err = snd_pcm_hw_refine(substream, params); - format_mask = *hw_param_mask(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); @@ -1826,7 +1825,10 @@ static int snd_pcm_oss_get_formats(struc 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)
Patches currently in stable-queue which might be from tiwai@suse.de are
queue-3.18/alsa-pcm-fix-uaf-in-snd_pcm_oss_get_formats.patch queue-3.18/alsa-seq-fix-possible-uaf-in-snd_seq_check_queue.patch queue-3.18/alsa-seq-clear-client-entry-before-deleting-else-at-closing.patch