| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Tue, 18 Dec 2018 11:18:34 -0600 |
| Subject: ALSA: rme9652: Fix potential Spectre v1 vulnerability |
| |
| commit 0b84304ef5da92add8dc75a1b07879c5374cdb05 upstream. |
| |
| info->channel 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/pci/rme9652/hdsp.c:4100 snd_hdsp_channel_info() warn: potential spectre issue 'hdsp->channel_map' [r] (local cap) |
| |
| Fix this by sanitizing info->channel before using it to index hdsp->channel_map |
| |
| 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]. |
| |
| Also, notice that I refactored the code a bit in order to get rid of the |
| following checkpatch warning: |
| |
| ERROR: do not use assignment in if condition |
| FILE: sound/pci/rme9652/hdsp.c:4103: |
| if ((mapped_channel = hdsp->channel_map[info->channel]) < 0) |
| |
| [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 |
| |
| Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| Signed-off-by: Takashi Iwai <tiwai@suse.de> |
| [bwh: Backported to 3.16: adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| sound/pci/rme9652/hdsp.c | 10 ++++++---- |
| 1 file changed, 6 insertions(+), 4 deletions(-) |
| |
| --- a/sound/pci/rme9652/hdsp.c |
| +++ b/sound/pci/rme9652/hdsp.c |
| @@ -29,6 +29,7 @@ |
| #include <linux/module.h> |
| #include <linux/math64.h> |
| #include <linux/vmalloc.h> |
| +#include <linux/nospec.h> |
| |
| #include <sound/core.h> |
| #include <sound/control.h> |
| @@ -4129,15 +4130,16 @@ static int snd_hdsp_channel_info(struct |
| struct snd_pcm_channel_info *info) |
| { |
| struct hdsp *hdsp = snd_pcm_substream_chip(substream); |
| - int mapped_channel; |
| + unsigned int channel = info->channel; |
| |
| - if (snd_BUG_ON(info->channel >= hdsp->max_channels)) |
| + if (snd_BUG_ON(channel >= hdsp->max_channels)) |
| return -EINVAL; |
| + channel = array_index_nospec(channel, hdsp->max_channels); |
| |
| - if ((mapped_channel = hdsp->channel_map[info->channel]) < 0) |
| + if (hdsp->channel_map[channel] < 0) |
| return -EINVAL; |
| |
| - info->offset = mapped_channel * HDSP_CHANNEL_BUFFER_BYTES; |
| + info->offset = hdsp->channel_map[channel] * HDSP_CHANNEL_BUFFER_BYTES; |
| info->first = 0; |
| info->step = 32; |
| return 0; |