[PATCH] drm/nouveau/mmu: Fix an UAF issue in NVKM

[korantwork@gmail.com]

From: Xinghui Li <korantli@tencent.com>

In nvkm_mem_new_host, the mem is be alloced. And mem->memory is
assigned to pmemory. During this process, the mem will be free if
the error occurs. But the *pmemory still points to the &mem->memory
which has been relased.Laterly, the nvkm_memory_unref will put the
memory which points to the pmemory again.So, we set the *pmemory to
NULL to avoid UAF issue.

Reported-by: loydlv <loydlv@tencent.com>
Signed-off-by: Xinghui Li <korantli@tencent.com>
---
 drivers/gpu/drm/nouveau/nvkm/subdev/mmu/mem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/mem.c b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/mem.c
index 92e363dbbc5a..ab30eb1fc0a3 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/mem.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/mem.c
@@ -185,6 +185,7 @@ nvkm_mem_new_host(struct nvkm_mmu *mmu, int type, u8 page, u64 size,
 	} else
 	if ( (ret = nvif_unvers(ret, &argv, &argc, args->vn))) {
 		kfree(mem);
+		*pmemory = NULL;
 		return ret;
 	}
 
-- 
2.31.1