staging: ccree: check DMA pool buf !NULL before free

commit 2f7caf6b upstream.

If we ran out of DMA pool buffers, we get into the unmap
code path with a NULL before. Deal with this by checking
the virtual mapping is not NULL.

Cc: stable@vger.kernel.org
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ccree/ssi_buffer_mgr.c

@@ -492,7 +492,8 @@ void ssi_buffer_mgr_unmap_blkcipher_request(
 				 DMA_TO_DEVICE);
 	}
 	/* Release pool */
-	if (req_ctx->dma_buf_type == SSI_DMA_BUF_MLLI) {
+	if (req_ctx->dma_buf_type == SSI_DMA_BUF_MLLI &&
+	    req_ctx->mlli_params.mlli_virt_addr) {
 		dma_pool_free(req_ctx->mlli_params.curr_pool,
 			      req_ctx->mlli_params.mlli_virt_addr,
 			      req_ctx->mlli_params.mlli_dma_addr);