crypto: mxs-dcp - Ensure payload is zero when using key slot

We could leak stack memory through the payload field when running
AES with a key from one of the hardware's key slots. Fix this by
ensuring the payload field is set to 0 in such cases.

This does not affect the common use case when the key is supplied
from main memory via the descriptor payload.
Signed-off-by: David Gstir <david@sigma-star.at>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202405270146.Y9tPoil8-lkp@intel.com/
Fixes: 3d16af0b ("crypto: mxs-dcp: Add support for hardware-bound keys")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/mxs-dcp.c

@@ -225,7 +225,8 @@ static int mxs_dcp_start_dma(struct dcp_async_ctx *actx)
 static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
 			   struct skcipher_request *req, int init)
 {
-	dma_addr_t key_phys, src_phys, dst_phys;
+	dma_addr_t key_phys = 0;
+	dma_addr_t src_phys, dst_phys;
 	struct dcp *sdcp = global_sdcp;
 	struct dcp_dma_desc *desc = &sdcp->coh->desc[actx->chan];
 	struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);