[PATCH v1] drm/shmem-helper: Remove another errant put in error path

[PATCH v1] drm/shmem-helper: Remove another errant put in error path

[Dmitry Osipenko]

drm_gem_shmem_mmap() doesn't own reference in error code path, resulting
in the dma-buf shmem GEM object getting prematurely freed leading to a
later use-after-free.

Fixes: f49a51bfdc8e ("drm/shme-helpers: Fix dma_buf_mmap forwarding bug")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index f21f47737817..8b20b41497e8 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -624,11 +624,14 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
 	int ret;
 
 	if (obj->import_attach) {
-		/* Drop the reference drm_gem_mmap_obj() acquired.*/
-		drm_gem_object_put(obj);
 		vma->vm_private_data = NULL;
+		ret = dma_buf_mmap(obj->dma_buf, vma, 0);
+
+		/* Drop the reference drm_gem_mmap_obj() acquired.*/
+		if (!ret)
+			drm_gem_object_put(obj);
 
-		return dma_buf_mmap(obj->dma_buf, vma, 0);
+		return ret;
 	}
 
 	ret = drm_gem_shmem_get_pages(shmem);
-- 
2.38.1

Re: [PATCH v1] drm/shmem-helper: Remove another errant put in error path

[Dmitry Osipenko]

On 1/9/23 00:13, Dmitry Osipenko wrote:
> drm_gem_shmem_mmap() doesn't own reference in error code path, resulting
> in the dma-buf shmem GEM object getting prematurely freed leading to a
> later use-after-free.
> 
> Fixes: f49a51bfdc8e ("drm/shme-helpers: Fix dma_buf_mmap forwarding bug")
> Cc: stable@vger.kernel.org
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index f21f47737817..8b20b41497e8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -624,11 +624,14 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
>  	int ret;
>  
>  	if (obj->import_attach) {
> -		/* Drop the reference drm_gem_mmap_obj() acquired.*/
> -		drm_gem_object_put(obj);
>  		vma->vm_private_data = NULL;
> +		ret = dma_buf_mmap(obj->dma_buf, vma, 0);
> +
> +		/* Drop the reference drm_gem_mmap_obj() acquired.*/
> +		if (!ret)
> +			drm_gem_object_put(obj);
>  
> -		return dma_buf_mmap(obj->dma_buf, vma, 0);
> +		return ret;
>  	}
>  
>  	ret = drm_gem_shmem_get_pages(shmem);

Rob, is this change still looking good to you? r-b? Thanks!

-- 
Best regards,
Dmitry

Re: [PATCH v1] drm/shmem-helper: Remove another errant put in error path

[Rob Clark]

On Sun, Jan 8, 2023 at 1:13 PM Dmitry Osipenko
<dmitry.osipenko@collabora.com> wrote:
>
> drm_gem_shmem_mmap() doesn't own reference in error code path, resulting
> in the dma-buf shmem GEM object getting prematurely freed leading to a
> later use-after-free.
>
> Fixes: f49a51bfdc8e ("drm/shme-helpers: Fix dma_buf_mmap forwarding bug")
> Cc: stable@vger.kernel.org
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: Rob Clark <robdclark@gmail.com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index f21f47737817..8b20b41497e8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -624,11 +624,14 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
>         int ret;
>
>         if (obj->import_attach) {
> -               /* Drop the reference drm_gem_mmap_obj() acquired.*/
> -               drm_gem_object_put(obj);
>                 vma->vm_private_data = NULL;
> +               ret = dma_buf_mmap(obj->dma_buf, vma, 0);
> +
> +               /* Drop the reference drm_gem_mmap_obj() acquired.*/
> +               if (!ret)
> +                       drm_gem_object_put(obj);
>
> -               return dma_buf_mmap(obj->dma_buf, vma, 0);
> +               return ret;
>         }
>
>         ret = drm_gem_shmem_get_pages(shmem);
> --
> 2.38.1
>

Re: [PATCH v1] drm/shmem-helper: Remove another errant put in error path

[Dmitry Osipenko]

On 2/16/23 18:35, Rob Clark wrote:
> On Sun, Jan 8, 2023 at 1:13 PM Dmitry Osipenko
> <dmitry.osipenko@collabora.com> wrote:
>>
>> drm_gem_shmem_mmap() doesn't own reference in error code path, resulting
>> in the dma-buf shmem GEM object getting prematurely freed leading to a
>> later use-after-free.
>>
>> Fixes: f49a51bfdc8e ("drm/shme-helpers: Fix dma_buf_mmap forwarding bug")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> 
> Reviewed-by: Rob Clark <robdclark@gmail.com>

Applied to misc-fixes

-- 
Best regards,
Dmitry