Re: [PATCH v4] vmci: prevent speculation leaks by sanitizing event in event_deliver()

[Vishnu Dasa]

On Tue, Apr 30, 2024 at 2:02 AM Hagar Hemdan <hagarhem@xxxxxxxxxx> wrote:
>
> From: Hagar Gamal Halim Hemdan <hagarhem@xxxxxxxxxx>
>
> Coverity spotted that event_msg is controlled by user-space,
> event_msg->event_data.event is passed to event_deliver() and used
> as an index without sanitization.
>
> This change ensures that the event index is sanitized to mitigate any
> possibility of speculative information leaks.
>
> This bug was discovered and resolved using Coverity Static Analysis
> Security Testing (SAST) by Synopsys, Inc.
>
> Only compile tested, no access to HW.
>
> Fixes: 1d990201f9bb ("VMCI: event handling implementation.")
> Signed-off-by: Hagar Gamal Halim Hemdan <hagarhem@xxxxxxxxxx>

Acked-by: Vishnu Dasa <vishnu.dasa@xxxxxxxxxxxx>

> ---
> v4: Added the testing state in the commit message and rebased on top of
> latest mainline
> ---
>  drivers/misc/vmw_vmci/vmci_event.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/vmw_vmci/vmci_event.c b/drivers/misc/vmw_vmci/vmci_event.c
> index 5d7ac07623c2..9a41ab65378d 100644
> --- a/drivers/misc/vmw_vmci/vmci_event.c
> +++ b/drivers/misc/vmw_vmci/vmci_event.c
> @@ -9,6 +9,7 @@
>  #include <linux/vmw_vmci_api.h>
>  #include <linux/list.h>
>  #include <linux/module.h>
> +#include <linux/nospec.h>
>  #include <linux/sched.h>
>  #include <linux/slab.h>
>  #include <linux/rculist.h>
> @@ -86,9 +87,12 @@ static void event_deliver(struct vmci_event_msg *event_msg)
>  {
>         struct vmci_subscription *cur;
>         struct list_head *subscriber_list;
> +       u32 sanitized_event, max_vmci_event;
>
>         rcu_read_lock();
> -       subscriber_list = &subscriber_array[event_msg->event_data.event];
> +       max_vmci_event = ARRAY_SIZE(subscriber_array);
> +       sanitized_event = array_index_nospec(event_msg->event_data.event, max_vmci_event);
> +       subscriber_list = &subscriber_array[sanitized_event];
>         list_for_each_entry_rcu(cur, subscriber_list, node) {
>                 cur->callback(cur->id, &event_msg->event_data,
>                               cur->callback_data);
> --
> 2.40.1
>