On 7/30/19 3:24 PM, Tony Luck wrote:
> Some processors may mispredict an array bounds check and
> speculatively access memory that they should not. With
> a user supplied array index we like to play things safe
> by masking the value with the array size before it is
> used as an index.
>
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> ---
>
> [I don't have h/w, so just compile tested]
>
> drivers/infiniband/core/user_mad.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
> index 9f8a48016b41..fdce254e4f65 100644
> --- a/drivers/infiniband/core/user_mad.c
> +++ b/drivers/infiniband/core/user_mad.c
> @@ -49,6 +49,7 @@
> #include <linux/sched.h>
> #include <linux/semaphore.h>
> #include <linux/slab.h>
> +#include <linux/nospec.h>
>
> #include <linux/uaccess.h>
>
> @@ -888,6 +889,7 @@ static int ib_umad_unreg_agent(struct ib_umad_file *file, u32 __user *arg)
> mutex_lock(&file->port->file_mutex);
> mutex_lock(&file->mutex);
>
> + id = array_index_nospec(id, IB_UMAD_MAX_AGENTS);
This is wrong. This prevents the below condition id >= IB_UMAD_MAX_AGENTS
from ever being true. And I don't think this is what you want.
> if (id >= IB_UMAD_MAX_AGENTS || !__get_agent(file, id)) {
> ret = -EINVAL;
> goto out;
>
--
Gustavo
