Memory used by KFD applications can contain sensitive information that should not be leaked to other processes. The current approach to prevent leaks is to clear VRAM at allocation time. This is not effective because memory can be reused in other ways without being cleared. Synchronously clearing memory on the allocation path also carries a significant performance penalty.

Stop clearing memory at allocation time. Instead mark the memory for wipe on release.

Signed-off-by: Felix Kuehling Felix.Kuehling@amd.com --- drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c index f5ecf28eb37c..2db6e498c069 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c @@ -1089,7 +1089,7 @@ int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu( */ if (flags & ALLOC_MEM_FLAGS_VRAM) { domain = alloc_domain = AMDGPU_GEM_DOMAIN_VRAM; - alloc_flags = AMDGPU_GEM_CREATE_VRAM_CLEARED; + alloc_flags = AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE; alloc_flags |= (flags & ALLOC_MEM_FLAGS_PUBLIC) ? AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED : AMDGPU_GEM_CREATE_NO_CPU_ACCESS;

Wipe VRAM memory containing sensitive data when moving or releasing BOs. Clearing the memory is pipelined to minimize any impact on subsequent memory allocation latency. Use of a poison value should help debug future use-after-free bugs.

When moving BOs, the existing ttm_bo_pipelined_move ensures that the memory won't be reused before being wiped.

When releasing BOs, the BO is fenced with the memory fill operation, which results in queuing the BO for a delayed delete.

v2: Move amdgpu_amdkfd_unreserve_memory_limit into amdgpu_bo_release_notify so that KFD can use memory that's still being cleared in the background

Signed-off-by: Felix Kuehling Felix.Kuehling@amd.com --- drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 39 ++++++++++++++++++++-- drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 1 + drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 17 ++++++++++ drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h | 2 ++ 4 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c index 989b7b55cb2e..f95f7a6509cc 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c @@ -80,9 +80,6 @@ static void amdgpu_bo_destroy(struct ttm_buffer_object *tbo) if (bo->pin_count > 0) amdgpu_bo_subtract_pin_size(bo);

- if (bo->kfd_bo) - amdgpu_amdkfd_unreserve_memory_limit(bo); - amdgpu_bo_kunmap(bo);

if (bo->gem_base.import_attach) @@ -1211,6 +1208,42 @@ void amdgpu_bo_move_notify(struct ttm_buffer_object *bo, trace_amdgpu_bo_move(abo, new_mem->mem_type, old_mem->mem_type); }

+/** + * amdgpu_bo_move_notify - notification about a BO being released + * @bo: pointer to a buffer object + * + * Wipes VRAM buffers whose contents should not be leaked before the + * memory is released. + */ +void amdgpu_bo_release_notify(struct ttm_buffer_object *bo) +{ + struct dma_fence *fence = NULL; + struct amdgpu_bo *abo; + int r; + + if (!amdgpu_bo_is_amdgpu_bo(bo)) + return; + + abo = ttm_to_amdgpu_bo(bo); + + if (abo->kfd_bo) + amdgpu_amdkfd_unreserve_memory_limit(abo); + + if (bo->mem.mem_type != TTM_PL_VRAM || !bo->mem.mm_node || + !(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE)) + return; + + reservation_object_lock(bo->resv, NULL); + + r = amdgpu_fill_buffer(abo, AMDGPU_POISON, bo->resv, &fence); + if (!WARN_ON(r)) { + amdgpu_bo_fence(abo, fence, false); + dma_fence_put(fence); + } + + reservation_object_unlock(bo->resv); +} + /** * amdgpu_bo_fault_reserve_notify - notification about a memory fault * @bo: pointer to a buffer object diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h index d60593cc436e..e302384fe003 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h @@ -265,6 +265,7 @@ int amdgpu_bo_get_metadata(struct amdgpu_bo *bo, void *buffer, void amdgpu_bo_move_notify(struct ttm_buffer_object *bo, bool evict, struct ttm_mem_reg *new_mem); +void amdgpu_bo_release_notify(struct ttm_buffer_object *bo); int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo); void amdgpu_bo_fence(struct amdgpu_bo *bo, struct dma_fence *fence, bool shared); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index eca2321e7a97..801f912a8578 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -439,6 +439,22 @@ static int amdgpu_move_blit(struct ttm_buffer_object *bo, if (r) goto error;

+ /* clear the space being freed */ + if (old_mem->mem_type == TTM_PL_VRAM && + (ttm_to_amdgpu_bo(bo)->flags & + AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE)) { + struct dma_fence *wipe_fence = NULL; + + r = amdgpu_fill_buffer(ttm_to_amdgpu_bo(bo), AMDGPU_POISON, + NULL, &wipe_fence); + if (r) { + goto error; + } else if (wipe_fence) { + dma_fence_put(fence); + fence = wipe_fence; + } + } + /* Always block for VM page tables before committing the new location */ if (bo->type == ttm_bo_type_kernel) r = ttm_bo_move_accel_cleanup(bo, fence, true, new_mem); @@ -1594,6 +1610,7 @@ static struct ttm_bo_driver amdgpu_bo_driver = { .move = &amdgpu_bo_move, .verify_access = &amdgpu_verify_access, .move_notify = &amdgpu_bo_move_notify, + .release_notify = &amdgpu_bo_release_notify, .fault_reserve_notify = &amdgpu_bo_fault_reserve_notify, .io_mem_reserve = &amdgpu_ttm_io_mem_reserve, .io_mem_free = &amdgpu_ttm_io_mem_free, diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h index caa76c693700..bccb8c49e597 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h @@ -38,6 +38,8 @@ #define AMDGPU_GTT_MAX_TRANSFER_SIZE 512 #define AMDGPU_GTT_NUM_TRANSFER_WINDOWS 2

+#define AMDGPU_POISON 0xd0bed0be + struct amdgpu_mman { struct ttm_bo_device bdev; bool mem_global_referenced;