Re: [PATCH] accel/qaic: Fix dereferencing freed memory

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Am 10.06.23 um 04:12 schrieb Sukrut Bellary:
smatch warning:
	drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
		dereferencing freed memory 'obj->import_attach'

obj->import_attach is detached and freed using dma_buf_detach().
But used after free to decrease the dmabuf ref count using
dma_buf_put().

Fixes: ff13be830333 ("accel/qaic: Add datapath")
Signed-off-by: Sukrut Bellary <sukrut.bellary@xxxxxxxxx>
---
  drivers/accel/qaic/qaic_data.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
index e42c1f9ffff8..7cba4d680ea8 100644
--- a/drivers/accel/qaic/qaic_data.c
+++ b/drivers/accel/qaic/qaic_data.c
@@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc
  static void qaic_free_object(struct drm_gem_object *obj)
  {
  	struct qaic_bo *bo = to_qaic_bo(obj);
+	struct dma_buf *dmabuf;

Maybe move that variable into the if.

if (obj->import_attach) {
  		/* DMABUF/PRIME Path */
+		dmabuf = obj->import_attach->dmabuf;
  		dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
-		dma_buf_put(obj->import_attach->dmabuf);
+		dma_buf_put(dmabuf);

I strongly assume you are not using the GEM prime helpers for this?

Christian.

  	} else {
  		/* Private buffer allocation path */
  		qaic_free_sgt(bo->sgt);




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