[PATCH] drm/prime: drop reference on imported dma-buf

Rob Clark rob.clark at linaro.org
Tue Sep 4 15:32:21 PDT 2012


Dave, I just noticed that I still have this patch locally, but don't
see it in drm-next..  so just checking that it didn't get forgotten

BR,
-R

On Tue, Jul 24, 2012 at 3:05 AM, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Tue, Jul 24, 2012 at 1:07 AM, Rob Clark <rob.clark at linaro.org> wrote:
>> From: Rob Clark <rob at ti.com>
>>
>> The GEM handle takes the reference.  If a driver is actually importing a
>> foreign dmabuf, rather than just re-importing it's own dmabuf, it needs
>> to do a get_dma_buf().
>>
>> Signed-off-by: Rob Clark <rob at ti.com>
> [Maybe mention that this is on top of my locking fixes.]
>
> We've discussed this a bit on irc and concluded that every function taking
> care of their own references to the dma buf works best in avoiding
> potential use-after-free issues when evil userspaces sneaks in a
> close(dma_buf_fd).
>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>> ---
>>  drivers/gpu/drm/drm_prime.c                |    7 +++++++
>>  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c |    4 ++++
>>  drivers/gpu/drm/i915/i915_gem_dmabuf.c     |    4 ++++
>>  drivers/gpu/drm/nouveau/nouveau_prime.c    |    5 +++++
>>  drivers/gpu/drm/radeon/radeon_prime.c      |    4 ++++
>>  drivers/gpu/drm/udl/udl_gem.c              |    4 ++++
>>  6 files changed, 28 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
>> index 4f80374..088e018 100644
>> --- a/drivers/gpu/drm/drm_prime.c
>> +++ b/drivers/gpu/drm/drm_prime.c
>> @@ -185,6 +185,13 @@ int drm_gem_prime_fd_to_handle(struct drm_device *dev,
>>         mutex_unlock(&file_priv->prime.lock);
>>         drm_gem_object_unreference_unlocked(obj);
>>
>> +       /*
>> +        * Drop the ref we obtained w/ dma_buf_get() for the benefit of
>> +        * drivers simply re-importing their own dma-buf.. if drivers
>> +        * import a foreign dma-buf, they should get_dma_buf().
>> +        */
>> +       dma_buf_put(dma_buf);
>> +
>>         return 0;
>>
>>  fail:
>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
>> index f270790..f8ac75b 100644
>> --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
>> +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
>> @@ -190,6 +190,9 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
>>                 }
>>         }
>>
>> +       /* since we are attaching, we need to hold a ref */
>> +       get_dma_buf(dma_buf);
>> +
>>         attach = dma_buf_attach(dma_buf, drm_dev->dev);
>>         if (IS_ERR(attach))
>>                 return ERR_PTR(-EINVAL);
>> @@ -250,6 +253,7 @@ err_unmap_attach:
>>         dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
>>  err_buf_detach:
>>         dma_buf_detach(dma_buf, attach);
>> +       dma_buf_put(dma_buf);
>>         return ERR_PTR(ret);
>>  }
>>
>> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
>> index cf6bdec..9d2b2eb 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
>> @@ -189,6 +189,9 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
>>                 }
>>         }
>>
>> +       /* since we are attaching, we need to hold a ref */
>> +       get_dma_buf(dma_buf);
>> +
>>         /* need to attach */
>>         attach = dma_buf_attach(dma_buf, dev->dev);
>>         if (IS_ERR(attach))
>> @@ -224,5 +227,6 @@ fail_unmap:
>>         dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
>>  fail_detach:
>>         dma_buf_detach(dma_buf, attach);
>> +       dma_buf_put(dma_buf);
>>         return ERR_PTR(ret);
>>  }
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c b/drivers/gpu/drm/nouveau/nouveau_prime.c
>> index 4c82801..fc30886 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_prime.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_prime.c
>> @@ -200,6 +200,10 @@ struct drm_gem_object *nouveau_gem_prime_import(struct drm_device *dev,
>>                         }
>>                 }
>>         }
>> +
>> +       /* since we are attaching, we need to hold a ref */
>> +       get_dma_buf(dma_buf);
>> +
>>         /* need to attach */
>>         attach = dma_buf_attach(dma_buf, dev->dev);
>>         if (IS_ERR(attach))
>> @@ -223,6 +227,7 @@ fail_unmap:
>>         dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
>>  fail_detach:
>>         dma_buf_detach(dma_buf, attach);
>> +       dma_buf_put(dma_buf);
>>         return ERR_PTR(ret);
>>  }
>>
>> diff --git a/drivers/gpu/drm/radeon/radeon_prime.c b/drivers/gpu/drm/radeon/radeon_prime.c
>> index 28f79ac..073a8d3 100644
>> --- a/drivers/gpu/drm/radeon/radeon_prime.c
>> +++ b/drivers/gpu/drm/radeon/radeon_prime.c
>> @@ -195,6 +195,9 @@ struct drm_gem_object *radeon_gem_prime_import(struct drm_device *dev,
>>                 }
>>         }
>>
>> +       /* since we are attaching, we need to hold a ref */
>> +       get_dma_buf(dma_buf);
>> +
>>         /* need to attach */
>>         attach = dma_buf_attach(dma_buf, dev->dev);
>>         if (IS_ERR(attach))
>> @@ -218,5 +221,6 @@ fail_unmap:
>>         dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
>>  fail_detach:
>>         dma_buf_detach(dma_buf, attach);
>> +       dma_buf_put(dma_buf);
>>         return ERR_PTR(ret);
>>  }
>> diff --git a/drivers/gpu/drm/udl/udl_gem.c b/drivers/gpu/drm/udl/udl_gem.c
>> index 7bd65bd..47f25d5 100644
>> --- a/drivers/gpu/drm/udl/udl_gem.c
>> +++ b/drivers/gpu/drm/udl/udl_gem.c
>> @@ -305,6 +305,9 @@ struct drm_gem_object *udl_gem_prime_import(struct drm_device *dev,
>>         struct udl_gem_object *uobj;
>>         int ret;
>>
>> +       /* since we are attaching, we need to hold a ref */
>> +       get_dma_buf(dma_buf);
>> +
>>         /* need to attach */
>>         attach = dma_buf_attach(dma_buf, dev->dev);
>>         if (IS_ERR(attach))
>> @@ -329,5 +332,6 @@ fail_unmap:
>>         dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
>>  fail_detach:
>>         dma_buf_detach(dma_buf, attach);
>> +       dma_buf_put(dma_buf);
>>         return ERR_PTR(ret);
>>  }
>> --
>> 1.7.9.5
>>
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>
>
>
> --
> Daniel Vetter
> daniel.vetter at ffwll.ch - +41 (0) 79 364 57 48 - http://blog.ffwll.ch
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel


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