Thanks for your feedback! We will remove the null tests according to your advice and prepare a V2 patch.

Best wishes, Tuo Li

On 2021/8/2 1:19, Christian König wrote:

Am 31.07.21 um 10:04 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_alloc() which is called in:    return ttm_pool_alloc(&adev->mman.bdev.pool, ttm, ctx);

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

NAK, the NULL test is just a leftover from when the objects where distinct.

Please remove the NULL test instead.

Regards, 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..80440f799c09 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -1120,8 +1120,11 @@ static int amdgpu_ttm_tt_populate(struct ttm_device *bdev,       struct amdgpu_device *adev = amdgpu_ttm_adev(bdev);       struct amdgpu_ttm_tt *gtt = (void *)ttm;   +    if (ttm == NULL) +        return -EINVAL;

/* user pages are bound by amdgpu_ttm_tt_pin_userptr() */ -    if (gtt && gtt->userptr) { +    if (gtt->userptr) {           ttm->sg = kzalloc(sizeof(struct sg_table), GFP_KERNEL);           if (!ttm->sg)               return -ENOMEM;