Re: [PATCH 1/4] staging: vc04_services: vchiq-mmal: fix OOB array access in event_to_host_cb()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sun, Mar 29, 2026 at 12:21:11AM -0600, Sebastian Josue Alba Vives wrote:
> From: Sebastián Alba Vives <sebasjosue84@gmail.com>
> 
> event_to_host_cb() uses msg->u.event_to_host.client_component as an
> index into the instance->component[] array (size VCHIQ_MMAL_MAX_COMPONENTS
> = 64) without any bounds validation. The client_component value comes
> from the VideoCore GPU firmware via VCHIQ message passing.
> 
> A malicious or buggy GPU firmware could send a crafted
> MMAL_MSG_TYPE_EVENT_TO_HOST message with client_component >= 64 (or
> negative), causing an out-of-bounds array access in kernel memory. This
> results in reading/dereferencing a bogus vchiq_mmal_component structure
> from memory beyond the array, which can lead to kernel crashes or
> potentially arbitrary kernel memory access.

The kernel trusts the hardware the driver is bound to, so this shouldn't
be happening ever, right?

> 
> Add a bounds check on comp_idx before using it as an array index.
> Move the component pointer assignment after the validation.
> 
> Fixes: b18ee53ad297 ("staging: bcm2835: Break MMAL support out from camera")
> Signed-off-by: Sebastián Alba Vives <sebasjosue84@gmail.com>

No cc: stable?

> ---
>  drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c b/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c
> index d36ad71cc..4772126d7 100644
> --- a/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c
> +++ b/drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c
> @@ -477,12 +477,19 @@ static void event_to_host_cb(struct vchiq_mmal_instance *instance,
>  			     struct mmal_msg *msg, u32 msg_len)
>  {
>  	int comp_idx = msg->u.event_to_host.client_component;
> -	struct vchiq_mmal_component *component =
> -					&instance->component[comp_idx];
> +	struct vchiq_mmal_component *component;
>  	struct vchiq_mmal_port *port = NULL;
>  	struct mmal_msg_context *msg_context;
>  	u32 port_num = msg->u.event_to_host.port_num;
>  
> +	if (comp_idx < 0 || comp_idx >= VCHIQ_MMAL_MAX_COMPONENTS) {
> +		pr_err("%s: component index %d out of range\n",
> +		       __func__, comp_idx);

dev_err() is best, right?

And are you going to allow a malicious hardware device to spam the
kernel log?  :)

thanks,

greg k-h