On 05/03/2018 11:17 AM, Gustavo A. R. Silva wrote:
> 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
Hi,
Just for (my) info: all of these types of patches are to prevent
what is loaded in cache when the index is out of range, right?
Not some random pool_info[random], but pool_info[valid, i.e., 0].
Since the value of pool is already sanity checked and -EINVAL is
returned when it's out of range.
Thanks.
> Cc: sta...@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>
> ---
> drivers/atm/zatm.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/atm/zatm.c b/drivers/atm/zatm.c
> index 1ef67db..9c9a229 100644
> --- a/drivers/atm/zatm.c
> +++ b/drivers/atm/zatm.c
> @@ -28,6 +28,7 @@
> #include <asm/io.h>
> #include <linux/atomic.h>
> #include <linux/uaccess.h>
> +#include <linux/nospec.h>
>
> #include "uPD98401.h"
> #include "uPD98402.h"
> @@ -1458,6 +1459,8 @@ static int zatm_ioctl(struct atm_dev *dev,unsigned int
> cmd,void __user *arg)
> 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) {
>
--
~Randy
