Commit 43c54b8c authored Jan 18, 2016 by Nicolas Boichat Committed by Takashi Iwai Jan 18, 2016

ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode



This reverts one hunk of
commit ef44a1ec ("ALSA: sound/core: use memdup_user()"), which
replaced a number of kmalloc followed by memcpy with memdup calls.

In this case, we are copying from a struct snd_pcm_hw_params32 to
a struct snd_pcm_hw_params, but the latter is 4 bytes longer than
the 32-bit version, so we need to separate kmalloc and copy calls.

This actually leads to an out-of-bounds memory access later on
in sound/soc/soc-pcm.c:soc_pcm_hw_params() (detected using KASan).

Fixes: ef44a1ec ('ALSA: sound/core: use memdup_user()')
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 2ba1fe7a

sound/core/pcm_compat.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -255,10 +255,15 @@ static int snd_pcm_ioctl_hw_params_compat(struct snd_pcm_substream *substream,
		if (! (runtime = substream->runtime))
		return -ENOTTY;

		/* only fifo_size is different, so just copy all */
		data = memdup_user(data32, sizeof(*data32));
		if (IS_ERR(data))
		return PTR_ERR(data);
		data = kmalloc(sizeof(*data), GFP_KERNEL);
		if (!data)
		return -ENOMEM;

		/* only fifo_size (RO from userspace) is different, so just copy all */
		if (copy_from_user(data, data32, sizeof(*data32))) {
		err = -EFAULT;
		goto error;
		}

		if (refine)
		err = snd_pcm_hw_refine(substream, data);

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