ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode

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@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 9 insertions, 4 deletions

diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c
index b48b434444ed..9630e9f72b7b 100644
--- a/sound/core/pcm_compat.c
+++ b/sound/core/pcm_compat.c
@@ -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);