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

From: Jeremy Cline <jcline-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Ben Skeggs <bskeggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: David Airlie <airlied-cv59FeDIM0c@public.gmane.org>,
	nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	Daniel Vetter <daniel-/w4YWyX8dFk@public.gmane.org>,
	Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Subject: [PATCH] drm/nouveau: avoid a use-after-free when BO init fails
Date: Wed,  2 Dec 2020 19:02:20 -0500	[thread overview]
Message-ID: <20201203000220.18238-1-jcline@redhat.com> (raw)

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-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Jeremy Cline <jcline-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 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
