Re: [PATCH v2] drm/xe/pt: Reset current_op in xe_pt_update_ops_init()

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Jul 14, 2026 at 11:24:32PM +0000, Zongyao Bai wrote:
> xe_pt_update_ops_init() fails to reset current_op to 0. On the
> vm_bind path, ops_execute() calls xe_pt_update_ops_prepare() inside
> the xe_validation_guard() / drm_exec_until_all_locked() loop. When
> that loop retries due to lock contention or OOM eviction
> (drm_exec_retry_on_contention() / xe_validation_retry_on_oom()),
> xe_pt_update_ops_prepare() runs again on the same vops, and each
> call to bind_op_prepare() increments current_op without resetting it.
> 
> After N retries current_op exceeds the array size allocated by
> xe_vma_ops_alloc(), causing an out-of-bounds write into
> SLUB-poisoned memory and a subsequent UAF crash in
> xe_migrate_update_pgtables_cpu() when reading the corrupted pt_op->bind.
> 
> Also reset needs_svm_lock and needs_invalidation which are derived in
> the same prepare pass and would otherwise cause wrong migrate ops
> selection and redundant TLB invalidation on retry.
> 
> Fix this by resetting current_op, needs_svm_lock and needs_invalidation
> in xe_pt_update_ops_init().
> 
> v2 (Matt):
>    - Add details in commit message.
>    - Add Fixes tag and Cc to stable@vger.kernel.org
> 
> Fixes: e8babb280b5e ("drm/xe: Convert multiple bind ops into single job")
> Suggested-by: Matthew Auld <matthew.auld@intel.com>
> Cc: stable@vger.kernel.org
> Assisted-by: GitHub-Copilot:claude-sonnet-4.6
> Signed-off-by: Zongyao Bai <zongyao.bai@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  drivers/gpu/drm/xe/xe_pt.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index e466f714bf86..598c6b2571e7 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -2371,8 +2371,11 @@ static void
>  xe_pt_update_ops_init(struct xe_vm_pgtable_update_ops *pt_update_ops)
>  {
>  	init_llist_head(&pt_update_ops->deferred);
> +	pt_update_ops->current_op = 0;
>  	pt_update_ops->start = ~0x0ull;
>  	pt_update_ops->last = 0x0ull;
> +	pt_update_ops->needs_svm_lock = false;
> +	pt_update_ops->needs_invalidation = false;
>  	xe_page_reclaim_list_init(&pt_update_ops->prl);
>  }
>  
> -- 
> 2.43.0
>