| From 4aea96f4237cea0c51a8bc87c0db31f0f932f1f0 Mon Sep 17 00:00:00 2001 |
| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Wed, 12 Dec 2018 11:20:49 -0600 |
| Subject: ALSA: emux: Fix potential Spectre v1 vulnerabilities |
| |
| From: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| |
| commit 4aea96f4237cea0c51a8bc87c0db31f0f932f1f0 upstream. |
| |
| info.mode and info.port are indirectly controlled by user-space, |
| hence leading to a potential exploitation of the Spectre variant 1 |
| vulnerability. |
| |
| These issues were detected with the help of Smatch: |
| |
| sound/synth/emux/emux_hwdep.c:72 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs[i]->ctrls' [w] (local cap) |
| sound/synth/emux/emux_hwdep.c:75 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs' [w] (local cap) |
| sound/synth/emux/emux_hwdep.c:75 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs[info.port]->ctrls' [w] (local cap) |
| |
| Fix this by sanitizing both info.mode and info.port before using them |
| to index emu->portptrs[i]->ctrls, emu->portptrs[info.port]->ctrls and |
| emu->portptrs. |
| |
| 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/synth/emux/emux_hwdep.c | 7 +++++-- |
| 1 file changed, 5 insertions(+), 2 deletions(-) |
| |
| --- a/sound/synth/emux/emux_hwdep.c |
| +++ b/sound/synth/emux/emux_hwdep.c |
| @@ -22,9 +22,9 @@ |
| #include <sound/core.h> |
| #include <sound/hwdep.h> |
| #include <linux/uaccess.h> |
| +#include <linux/nospec.h> |
| #include "emux_voice.h" |
| |
| - |
| #define TMP_CLIENT_ID 0x1001 |
| |
| /* |
| @@ -66,13 +66,16 @@ snd_emux_hwdep_misc_mode(struct snd_emux |
| return -EFAULT; |
| if (info.mode < 0 || info.mode >= EMUX_MD_END) |
| return -EINVAL; |
| + info.mode = array_index_nospec(info.mode, EMUX_MD_END); |
| |
| if (info.port < 0) { |
| for (i = 0; i < emu->num_ports; i++) |
| emu->portptrs[i]->ctrls[info.mode] = info.value; |
| } else { |
| - if (info.port < emu->num_ports) |
| + if (info.port < emu->num_ports) { |
| + info.port = array_index_nospec(info.port, emu->num_ports); |
| emu->portptrs[info.port]->ctrls[info.mode] = info.value; |
| + } |
| } |
| return 0; |
| } |