[PATCH 3/4] drm/xe/guc: Don't read data from G2H prior to length check

[Matthew Brost]

On Tue, Nov 05, 2024 at 06:30:31PM +0100, Michal Wajdeczko wrote:
> While highly unlikely, incoming G2H message might be too short
> so we shouldn't read any data from it prior to checking a length.
> 

Is this really needed though? The *msg is a per CT member:

xe_guc_ct_types.h

147         /** @msg: Message buffer */
148         u32 msg[GUC_CTB_MSG_MAX_LEN];
149         /** @fast_msg: Message buffer */
150         u32 fast_msg[GUC_CTB_MSG_MAX_LEN];


I suppose this good practice but this is not an actual problem though, right?

Matt 

> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Cc: Matthew Brost <matthew.brost at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_submit.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 4481890be941..147000fd1177 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -1885,12 +1885,14 @@ static void handle_sched_done(struct xe_guc *guc, struct xe_exec_queue *q,
>  int xe_guc_sched_done_handler(struct xe_guc *guc, u32 *msg, u32 len)
>  {
>  	struct xe_exec_queue *q;
> -	u32 guc_id = msg[0];
> -	u32 runnable_state = msg[1];
> +	u32 guc_id, runnable_state;
>  
>  	if (unlikely(len < 2))
>  		return -EPROTO;
>  
> +	guc_id = msg[0];
> +	runnable_state = msg[1];
> +
>  	q = g2h_exec_queue_lookup(guc, guc_id);
>  	if (unlikely(!q))
>  		return -EPROTO;
> @@ -1924,11 +1926,13 @@ static void handle_deregister_done(struct xe_guc *guc, struct xe_exec_queue *q)
>  int xe_guc_deregister_done_handler(struct xe_guc *guc, u32 *msg, u32 len)
>  {
>  	struct xe_exec_queue *q;
> -	u32 guc_id = msg[0];
> +	u32 guc_id;
>  
>  	if (unlikely(len < 1))
>  		return -EPROTO;
>  
> +	guc_id = msg[0];
> +
>  	q = g2h_exec_queue_lookup(guc, guc_id);
>  	if (unlikely(!q))
>  		return -EPROTO;
> @@ -1950,11 +1954,13 @@ int xe_guc_exec_queue_reset_handler(struct xe_guc *guc, u32 *msg, u32 len)
>  {
>  	struct xe_gt *gt = guc_to_gt(guc);
>  	struct xe_exec_queue *q;
> -	u32 guc_id = msg[0];
> +	u32 guc_id;
>  
>  	if (unlikely(len < 1))
>  		return -EPROTO;
>  
> +	guc_id = msg[0];
> +
>  	q = g2h_exec_queue_lookup(guc, guc_id);
>  	if (unlikely(!q))
>  		return -EPROTO;
> @@ -2010,11 +2016,13 @@ int xe_guc_exec_queue_memory_cat_error_handler(struct xe_guc *guc, u32 *msg,
>  {
>  	struct xe_gt *gt = guc_to_gt(guc);
>  	struct xe_exec_queue *q;
> -	u32 guc_id = msg[0];
> +	u32 guc_id;
>  
>  	if (unlikely(len < 1))
>  		return -EPROTO;
>  
> +	guc_id = msg[0];
> +
>  	q = g2h_exec_queue_lookup(guc, guc_id);
>  	if (unlikely(!q))
>  		return -EPROTO;
> -- 
> 2.43.0
>