Re: [PATCH v3 1/1] drm/ttm: Fix COW check

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Am 13.07.21 um 00:06 schrieb Felix Kuehling:
KFD Thunk maps invisible VRAM BOs with PROT_NONE, MAP_PRIVATE.
is_cow_mapping returns true for these mappings. Add a check for
vm_flags & VM_WRITE to avoid mmap failures on private read-only or
PROT_NONE mappings.

v2: protect against mprotect making a mapping writable after the fact
v3: update driver-specific vm_operations_structs

Fixes: f91142c62161 ("drm/ttm: nuke VM_MIXEDMAP on BO mappings v3")
Signed-off-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>

Reviewed-by: Christian König <christian.koenig@xxxxxxx>

---
  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c  |  3 ++-
  drivers/gpu/drm/nouveau/nouveau_gem.c    |  3 ++-
  drivers/gpu/drm/radeon/radeon_gem.c      |  3 ++-
  drivers/gpu/drm/ttm/ttm_bo_vm.c          | 14 +++++++++++++-
  drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c |  1 +
  include/drm/ttm/ttm_bo_api.h             |  4 ++++
  6 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index b3404c43a911..1aa750a6a5d2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -79,7 +79,8 @@ static const struct vm_operations_struct amdgpu_gem_vm_ops = {
  	.fault = amdgpu_gem_fault,
  	.open = ttm_bo_vm_open,
  	.close = ttm_bo_vm_close,
-	.access = ttm_bo_vm_access
+	.access = ttm_bo_vm_access,
+	.mprotect = ttm_bo_vm_mprotect
  };
static void amdgpu_gem_object_free(struct drm_gem_object *gobj)
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index 5b27845075a1..164ea564bb7a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -70,7 +70,8 @@ static const struct vm_operations_struct nouveau_ttm_vm_ops = {
  	.fault = nouveau_ttm_fault,
  	.open = ttm_bo_vm_open,
  	.close = ttm_bo_vm_close,
-	.access = ttm_bo_vm_access
+	.access = ttm_bo_vm_access,
+	.mprotect = ttm_bo_vm_mprotect
  };
void
diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index 458f92a70887..c19ad07eb7b5 100644
--- a/drivers/gpu/drm/radeon/radeon_gem.c
+++ b/drivers/gpu/drm/radeon/radeon_gem.c
@@ -77,7 +77,8 @@ static const struct vm_operations_struct radeon_gem_vm_ops = {
  	.fault = radeon_gem_fault,
  	.open = ttm_bo_vm_open,
  	.close = ttm_bo_vm_close,
-	.access = ttm_bo_vm_access
+	.access = ttm_bo_vm_access,
+	.mprotect = ttm_bo_vm_mprotect
  };
static void radeon_gem_object_free(struct drm_gem_object *gobj)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index f56be5bc0861..fb325bad5db6 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -542,17 +542,29 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
  }
  EXPORT_SYMBOL(ttm_bo_vm_access);
+int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
+		       unsigned long end, unsigned long newflags)
+{
+	/* Enforce no COW since would have really strange behavior with it. */
+	if (is_cow_mapping(newflags) && (newflags & VM_WRITE))
+		return -EINVAL;
+
+	return 0;
+}
+EXPORT_SYMBOL(ttm_bo_vm_mprotect);
+
  static const struct vm_operations_struct ttm_bo_vm_ops = {
  	.fault = ttm_bo_vm_fault,
  	.open = ttm_bo_vm_open,
  	.close = ttm_bo_vm_close,
  	.access = ttm_bo_vm_access,
+	.mprotect = ttm_bo_vm_mprotect,
  };
int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
  {
  	/* Enforce no COW since would have really strange behavior with it. */
-	if (is_cow_mapping(vma->vm_flags))
+	if (is_cow_mapping(vma->vm_flags) && (vma->vm_flags & VM_WRITE))
  		return -EINVAL;
ttm_bo_get(bo);
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
index e6b1f98ec99f..e4bf7dc99320 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
@@ -61,6 +61,7 @@ int vmw_mmap(struct file *filp, struct vm_area_struct *vma)
  		.fault = vmw_bo_vm_fault,
  		.open = ttm_bo_vm_open,
  		.close = ttm_bo_vm_close,
+		.mprotect = ttm_bo_vm_mprotect,
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  		.huge_fault = vmw_bo_vm_huge_fault,
  #endif
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index f681bbdbc698..40eb95875355 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -605,6 +605,10 @@ void ttm_bo_vm_close(struct vm_area_struct *vma);
int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
  		     void *buf, int len, int write);
+
+int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
+		       unsigned long end, unsigned long newflags);
+
  bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all);
vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot);

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