| From 701956d4018e5d5438570e39e8bda47edd32c489 Mon Sep 17 00:00:00 2001 |
| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Wed, 9 Jan 2019 13:02:36 -0600 |
| Subject: char/mwave: fix potential Spectre v1 vulnerability |
| |
| From: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| |
| commit 701956d4018e5d5438570e39e8bda47edd32c489 upstream. |
| |
| ipcnum 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: |
| |
| drivers/char/mwave/mwavedd.c:299 mwave_ioctl() warn: potential spectre issue 'pDrvData->IPCs' [w] (local cap) |
| |
| Fix this by sanitizing ipcnum before using it to index pDrvData->IPCs. |
| |
| 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 |
| |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/char/mwave/mwavedd.c | 7 +++++++ |
| 1 file changed, 7 insertions(+) |
| |
| --- a/drivers/char/mwave/mwavedd.c |
| +++ b/drivers/char/mwave/mwavedd.c |
| @@ -59,6 +59,7 @@ |
| #include <linux/mutex.h> |
| #include <linux/delay.h> |
| #include <linux/serial_8250.h> |
| +#include <linux/nospec.h> |
| #include "smapi.h" |
| #include "mwavedd.h" |
| #include "3780i.h" |
| @@ -289,6 +290,8 @@ static long mwave_ioctl(struct file *fil |
| ipcnum); |
| return -EINVAL; |
| } |
| + ipcnum = array_index_nospec(ipcnum, |
| + ARRAY_SIZE(pDrvData->IPCs)); |
| PRINTK_3(TRACE_MWAVE, |
| "mwavedd::mwave_ioctl IOCTL_MW_REGISTER_IPC" |
| " ipcnum %x entry usIntCount %x\n", |
| @@ -317,6 +320,8 @@ static long mwave_ioctl(struct file *fil |
| " Invalid ipcnum %x\n", ipcnum); |
| return -EINVAL; |
| } |
| + ipcnum = array_index_nospec(ipcnum, |
| + ARRAY_SIZE(pDrvData->IPCs)); |
| PRINTK_3(TRACE_MWAVE, |
| "mwavedd::mwave_ioctl IOCTL_MW_GET_IPC" |
| " ipcnum %x, usIntCount %x\n", |
| @@ -383,6 +388,8 @@ static long mwave_ioctl(struct file *fil |
| ipcnum); |
| return -EINVAL; |
| } |
| + ipcnum = array_index_nospec(ipcnum, |
| + ARRAY_SIZE(pDrvData->IPCs)); |
| mutex_lock(&mwave_mutex); |
| if (pDrvData->IPCs[ipcnum].bIsEnabled == true) { |
| pDrvData->IPCs[ipcnum].bIsEnabled = false; |