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ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode 

This reverts one hunk of
commit ef44a1ec6e ("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: ef44a1ec6e ('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>
This commit is contained in:
Nicolas Boichat 2016-01-18 21:35:00 +08:00 committed by Takashi Iwai
parent 2ba1fe7a06
commit 43c54b8c7c
1 changed files with 9 additions and 4 deletions
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13
sound/core/pcm_compat.c
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@ -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);