| From 94ffb030b6d31ec840bb811be455dd2e26a4f43e Mon Sep 17 00:00:00 2001 |
| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Wed, 12 Dec 2018 15:36:28 -0600 |
| Subject: ALSA: pcm: Fix potential Spectre v1 vulnerability |
| |
| From: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| |
| commit 94ffb030b6d31ec840bb811be455dd2e26a4f43e upstream. |
| |
| stream is indirectly controlled by user-space, hence leading to |
| a potential exploitation of the Spectre variant 1 vulnerability. |
| |
| This issue was detected with the help of Smatch: |
| |
| sound/core/pcm.c:140 snd_pcm_control_ioctl() warn: potential spectre issue 'pcm->streams' [r] (local cap) |
| |
| Fix this by sanitizing stream before using it to index pcm->streams |
| |
| Notice that given that speculation windows are large, the policy is |
| to kill the speculation on the first load and not worry if it can be |
| completed with a dependent load/store [1]. |
| |
| [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 |
| |
| Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Takashi Iwai <tiwai@suse.de> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| sound/core/pcm.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| --- a/sound/core/pcm.c |
| +++ b/sound/core/pcm.c |
| @@ -25,6 +25,7 @@ |
| #include <linux/time.h> |
| #include <linux/mutex.h> |
| #include <linux/device.h> |
| +#include <linux/nospec.h> |
| #include <sound/core.h> |
| #include <sound/minors.h> |
| #include <sound/pcm.h> |
| @@ -125,6 +126,7 @@ static int snd_pcm_control_ioctl(struct |
| return -EFAULT; |
| if (stream < 0 || stream > 1) |
| return -EINVAL; |
| + stream = array_index_nospec(stream, 2); |
| if (get_user(subdevice, &info->subdevice)) |
| return -EFAULT; |
| mutex_lock(®ister_mutex); |