Re: [PATCH] drm/xe/xe_migrate: Fix potential overflows expression

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, Mar 20, 2024 at 03:48:35PM +0530, Himal Prasad Ghimiray wrote:
> Cast to proper datatypes to avoid overflows.

I'm afraid that the cast wont prevent the overflow, but mask it.
probably safer to move the multiplication to some of the helpers
in linux/math64.h ?!

> 
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> ---
> These errors were highlighted by Coverity. I'm uncertain whether they
> require attention or if it would be more appropriate to label them as
> false positives within the tool.
> 
> I've submitted this patch in case addressing the issues is necessary.
> However, if reviewers determine that these issues should be marked as
> false positives or ignored within the tool, that option is also
> available
> 
>  drivers/gpu/drm/xe/xe_migrate.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index ee1bb938c493..2ba4fb9511f6 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -227,7 +227,7 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
>  		if (vm->flags & XE_VM_FLAG_64K && level == 1)
>  			flags = XE_PDE_64K;
>  
> -		entry = vm->pt_ops->pde_encode_bo(bo, map_ofs + (level - 1) *
> +		entry = vm->pt_ops->pde_encode_bo(bo, map_ofs + (u64)(level - 1) *
>  						  XE_PAGE_SIZE, pat_index);
>  		xe_map_wr(xe, &bo->vmap, map_ofs + XE_PAGE_SIZE * level, u64,
>  			  entry | flags);
> @@ -235,7 +235,7 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
>  
>  	/* Write PDE's that point to our BO. */
>  	for (i = 0; i < num_entries - num_level; i++) {
> -		entry = vm->pt_ops->pde_encode_bo(bo, i * XE_PAGE_SIZE,
> +		entry = vm->pt_ops->pde_encode_bo(bo, (u64)i * XE_PAGE_SIZE,
>  						  pat_index);
>  
>  		xe_map_wr(xe, &bo->vmap, map_ofs + XE_PAGE_SIZE +
> @@ -291,7 +291,7 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
>  #define VM_SA_UPDATE_UNIT_SIZE		(XE_PAGE_SIZE / NUM_VMUSA_UNIT_PER_PAGE)
>  #define NUM_VMUSA_WRITES_PER_UNIT	(VM_SA_UPDATE_UNIT_SIZE / sizeof(u64))
>  	drm_suballoc_manager_init(&m->vm_update_sa,
> -				  (map_ofs / XE_PAGE_SIZE - NUM_KERNEL_PDE) *
> +				  (size_t)(map_ofs / XE_PAGE_SIZE - NUM_KERNEL_PDE) *
>  				  NUM_VMUSA_UNIT_PER_PAGE, 0);
>  
>  	m->pt_bo = bo;
> @@ -490,7 +490,7 @@ static void emit_pte(struct xe_migrate *m,
>  	struct xe_vm *vm = m->q->vm;
>  	u16 pat_index;
>  	u32 ptes;
> -	u64 ofs = at_pt * XE_PAGE_SIZE;
> +	u64 ofs = (u64)at_pt * XE_PAGE_SIZE;
>  	u64 cur_ofs;
>  
>  	/* Indirect access needs compression enabled uncached PAT index */
> -- 
> 2.25.1
>