From: "Christian König" <christian.koenig@amd.com>
To: Robert Beckett <bob.beckett@collabora.com>,
dri-devel@lists.freedesktop.org, Huang Rui <ray.huang@amd.com>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Matthew Auld <matthew.auld@intel.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/ttm: fix potential null ptr deref in when mem space alloc fails
Date: Mon, 21 Mar 2022 10:51:38 +0100 [thread overview]
Message-ID: <8688c626-5858-18ba-593b-cdf179ca5201@amd.com> (raw)
In-Reply-To: <20220318195004.416539-1-bob.beckett@collabora.com>
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;
next prev parent reply other threads:[~2022-03-21 9:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-18 19:50 [PATCH] drm/ttm: fix potential null ptr deref in when mem space alloc fails Robert Beckett
2022-03-21 9:51 ` Christian König [this message]
2022-03-21 15:44 ` Robert Beckett
2022-03-22 7:17 ` Christian König
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