[PATCH] dma-buf: Move dma_resv_assert_held() after input validation

[lirongqing]

From: Li RongQing <lirongqing@xxxxxxxxx>

Move dma_resv_assert_held() after the validation of 'attach' and
'attach->dmabuf' to avoid a potential null pointer dereference if
the function is ever called with invalid arguments.

Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
---
 drivers/dma-buf/dma-buf-mapping.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/dma-buf-mapping.c b/drivers/dma-buf/dma-buf-mapping.c
index 794acff..e6ecd6c 100644
--- a/drivers/dma-buf/dma-buf-mapping.c
+++ b/drivers/dma-buf/dma-buf-mapping.c
@@ -102,12 +102,12 @@ struct sg_table *dma_buf_phys_vec_to_sgt(struct dma_buf_attachment *attach,
 	size_t i;
 	int ret;
 
-	dma_resv_assert_held(attach->dmabuf->resv);
-
 	if (WARN_ON(!attach || !attach->dmabuf || !provider))
 		/* This function is supposed to work on MMIO memory only */
 		return ERR_PTR(-EINVAL);
 
+	dma_resv_assert_held(attach->dmabuf->resv);
+
 	dma = kzalloc_obj(*dma);
 	if (!dma)
 		return ERR_PTR(-ENOMEM);
-- 
2.9.4