| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Thu, 3 May 2018 13:17:12 -0500 |
| Subject: atm: zatm: Fix potential Spectre v1 |
| |
| commit 2be147f7459db5bbf292e0a6f135037b55e20b39 upstream. |
| |
| pool can be 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/atm/zatm.c:1462 zatm_ioctl() warn: potential spectre issue |
| 'zatm_dev->pool_info' (local cap) |
| |
| Fix this by sanitizing pool before using it to index |
| zatm_dev->pool_info |
| |
| 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> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| [bwh: Backported to 3.16: adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| drivers/atm/zatm.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- a/drivers/atm/zatm.c |
| +++ b/drivers/atm/zatm.c |
| @@ -28,6 +28,7 @@ |
| #include <asm/io.h> |
| #include <linux/atomic.h> |
| #include <asm/uaccess.h> |
| +#include <linux/nospec.h> |
| |
| #include "uPD98401.h" |
| #include "uPD98402.h" |
| @@ -1455,6 +1456,8 @@ static int zatm_ioctl(struct atm_dev *de |
| return -EFAULT; |
| if (pool < 0 || pool > ZATM_LAST_POOL) |
| return -EINVAL; |
| + pool = array_index_nospec(pool, |
| + ZATM_LAST_POOL + 1); |
| spin_lock_irqsave(&zatm_dev->lock, flags); |
| info = zatm_dev->pool_info[pool]; |
| if (cmd == ZATM_GETPOOLZ) { |
