Re: [PATCH] drm/amdkfd: Fix a race condition of vram buffer unref in svm code

[Eric Huang]

On 2023-09-26 23:00, Xiaogang.Chen wrote:

From: Xiaogang Chen <xiaogang.c...@amd.com>

prange->svm_bo unref can happen in both mmu callback and a callback after
migrate to system ram. Both are async call in different tasks. Sync svm_bo
unref operation to avoid random "use-after-free".

Signed-off-by: Xiaogang.Chen <xiaogang.c...@amd.com>
---
  drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 9 +++++++++
  1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 70aa882636ab..8e246e848018 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -637,6 +637,15 @@ void svm_range_vram_node_free(struct svm_range *prange)
  {
        svm_range_bo_unref(prange->svm_bo);
        prange->ttm_res = NULL;

Are above two lines not removed?

Regards,
Eric

+       /* serialize prange->svm_bo unref */
+       mutex_lock(&prange->lock);
+       /* prange->svm_bo has not been unref */
+       if (prange->ttm_res) {
+               prange->ttm_res = NULL;
+               mutex_unlock(&prange->lock);
+               svm_range_bo_unref(prange->svm_bo);
+       } else
+               mutex_unlock(&prange->lock);
  }

struct kfd_node *