Patch "ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-pcm-fix-snd_pcm_hw_params-struct-copy-in-compat-mode.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nicolas Boichat <[email protected]>
Date: Mon, 18 Jan 2016 21:35:00 +0800
Subject: ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode

From: Nicolas Boichat <[email protected]>

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).

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

@@ -255,10 +255,15 @@ 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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/alsa-pcm-fix-snd_pcm_hw_params-struct-copy-in-compat-mode.patch queue-4.3/alsa-seq-fix-snd_seq_call_port_info_ioctl-in-compat-mode.patch