Re: [PATCH v4 2/5] drm/xe/svm: Fix a potential bo UAF

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 26-03-2025 13:35, Thomas Hellström wrote:
> If drm_gpusvm_migrate_to_devmem() succeeds, if a cpu access happens to the
> range the bo may be freed before xe_bo_unlock(), causing a UAF.
> 
> Since the reference is transferred, use xe_svm_devmem_release() to
> release the reference on drm_gpusvm_migrate_to_devmem() failure,
> and hold a local reference to protect the UAF.

Fixes tag ?

> 
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Reviewed-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_svm.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> index 52613dd8573a..c7424c824a14 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -702,11 +702,14 @@ static int xe_svm_alloc_vram(struct xe_vm *vm, struct xe_tile *tile,
>   	list_for_each_entry(block, blocks, link)
>   		block->private = vr;
>   
> +	xe_bo_get(bo);
>   	err = drm_gpusvm_migrate_to_devmem(&vm->svm.gpusvm, &range->base,
>   					   &bo->devmem_allocation, ctx);
> -	xe_bo_unlock(bo);
>   	if (err)
> -		xe_bo_put(bo);	/* Creation ref */
> +		xe_svm_devmem_release(&bo->devmem_allocation);
> +
> +	xe_bo_unlock(bo);
> +	xe_bo_put(bo);
>   
>   unlock:
>   	mmap_read_unlock(mm);