Am 31.07.21 um 10:13 schrieb Tuo Li:

The variable ttm is assigned to the variable gtt, and the variable gtt is checked in: if (gtt && gtt->userptr)

This indicates that both ttm and gtt can be NULL. If so, a null-pointer dereference will occur: if (ttm->page_flags & TTM_PAGE_FLAG_SG)

Also, some null-pointer dereferences will occur in the function ttm_pool_free() which is called in: return ttm_pool_free(&adev->mman.bdev.pool, ttm);

To fix these possible null-pointer dereferences, the function returns when ttm is NULL.

NAK, same as with the other patch.

The ttm object is mandatory, asking the driver to destroy a ttm object which doesn't exists makes no sense at all and is a bug in the upper layer.

The NULL check is just a leftover from when the gtt and ttm objects where distinct. Please remove that one instead.

BTW: Bonus points for changing the (void *) cast into a much cleaner container_of().

Thanks, Christian.

Reported-by: TOTE Robot oslab@tsinghua.edu.cn Signed-off-by: Tuo Li islituo@gmail.com

---

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index 3a55f08e00e1..0216ca085f11 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -1146,7 +1146,10 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_device *bdev, struct amdgpu_ttm_tt *gtt = (void *)ttm; struct amdgpu_device *adev;

• if (gtt && gtt->userptr) {

• if (ttm == NULL)

• return;
  

• if (gtt->userptr) { amdgpu_ttm_tt_set_user_pages(ttm, NULL); kfree(ttm->sg); ttm->sg = NULL;