[PATCH 3.14 20/59] ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode

From: Greg Kroah-Hartman
Date: Wed Jan 27 2016 - 14:28:57 EST

3.14-stable review patch. If anyone has any objections, please let me know.


From: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>

commit 43c54b8c7cfe22f868a751ba8a59abf1724160b1 upstream.

This reverts one hunk of
commit ef44a1ec6eee ("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: ef44a1ec6eee ('ALSA: sound/core: use memdup_user()')
Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

sound/core/pcm_compat.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

--- a/sound/core/pcm_compat.c
+++ b/sound/core/pcm_compat.c
@@ -236,10 +236,15 @@ static int snd_pcm_ioctl_hw_params_compa
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);