Messages in this thread | | | Date | Mon, 21 Mar 2022 10:51:38 +0100 | Subject | Re: [PATCH] drm/ttm: fix potential null ptr deref in when mem space alloc fails | From | Christian König <> |
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Am 18.03.22 um 20:50 schrieb Robert Beckett: > when allocating a resource in place it is common to free the buffer's > resource, then allocate a new resource in a different placement. > > e.g. amdgpu_bo_create_kernel_at calls ttm_resource_free, then calls > ttm_bo_mem_space.
Well yes I'm working the drivers towards this, but NAK at the moment. Currently bo->resource is never expected to be NULL.
And yes I'm searching for this bug in amdgpu for quite a while. Where exactly does that happen?
Amdgpu is supposed to allocate a new resource first, then do a swap and the free the old one.
Thanks, Christian.
> > In this situation, bo->resource will be null as it is cleared during > the initial freeing of the previous resource. > This leads to a null deref. > > Fixes: d3116756a710 (drm/ttm: rename bo->mem and make it a pointer) > > Signed-off-by: Robert Beckett <bob.beckett@collabora.com> > --- > drivers/gpu/drm/ttm/ttm_bo.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c > index db3dc7ef5382..62b29ee7d040 100644 > --- a/drivers/gpu/drm/ttm/ttm_bo.c > +++ b/drivers/gpu/drm/ttm/ttm_bo.c > @@ -875,7 +875,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo, > } > > error: > - if (bo->resource->mem_type == TTM_PL_SYSTEM && !bo->pin_count) > + if (bo->resource && bo->resource->mem_type == TTM_PL_SYSTEM && !bo->pin_count) > ttm_bo_move_to_lru_tail_unlocked(bo); > > return ret;
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