Nouveau - Dec 2020 - [PATCH] drm/nouveau: avoid a use-after-free when BO init fails

nouveau_bo_init() is backed by ttm_bo_init() and ferries its return code
back to the caller. On failures, ttm_bo_init() invokes the provided
destructor which should de-initialize and free the memory.

Thus, when nouveau_bo_init() returns an error the gem object has already
been released and the memory freed by nouveau_bo_del_ttm().

Fixes: 019cbd4a4feb ("drm/nouveau: Initialize GEM object before TTM
object")
Cc: Thierry Reding <treding at nvidia.com>
Signed-off-by: Jeremy Cline <jcline at redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_gem.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c
b/drivers/gpu/drm/nouveau/nouveau_gem.c
index 787d05eefd9c..d30157cc7169 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -211,10 +211,8 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int
align, uint32_t domain,
 	}
 
 	ret = nouveau_bo_init(nvbo, size, align, domain, NULL, NULL);
-	if (ret) {
-		nouveau_bo_ref(NULL, &nvbo);
+	if (ret)
 		return ret;
-	}
 
 	/* we restrict allowed domains on nv50+ to only the types
 	 * that were requested at creation time.  not possibly on
-- 
2.28.0

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Wed, 2020-12-02 at 19:02 -0500, Jeremy Cline wrote:
> nouveau_bo_init() is backed by ttm_bo_init() and ferries its return code
> back to the caller. On failures, ttm_bo_init() invokes the provided
> destructor which should de-initialize and free the memory.
> 
> Thus, when nouveau_bo_init() returns an error the gem object has already
> been released and the memory freed by nouveau_bo_del_ttm().
> 
> Fixes: 019cbd4a4feb ("drm/nouveau: Initialize GEM object before TTM
object")
> Cc: Thierry Reding <treding at nvidia.com>
> Signed-off-by: Jeremy Cline <jcline at redhat.com>
> ---
> ?drivers/gpu/drm/nouveau/nouveau_gem.c | 4 +---
> ?1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c
> b/drivers/gpu/drm/nouveau/nouveau_gem.c
> index 787d05eefd9c..d30157cc7169 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> @@ -211,10 +211,8 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int
> align, uint32_t domain,
> ????????}
> ?
> ????????ret = nouveau_bo_init(nvbo, size, align, domain, NULL, NULL);
> -???????if (ret) {
> -???????????????nouveau_bo_ref(NULL, &nvbo);
> +???????if (ret)
> ????????????????return ret;
> -???????}
> ?
> ????????/* we restrict allowed domains on nv50+ to only the types
> ???????? * that were requested at creation time.? not possibly on
-- 
Sincerely,
   Lyude Paul (she/her)
   Software Engineer at Red Hat
   
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