linux-kernel - [RESEND 2/2] spi: spi-zynq-qspi: Fix stack violation bug

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Date:   Wed, 28 Apr 2021 23:38:02 -0600
From:   Amit Kumar Mahapatra <amit.kumar-mahapatra@...inx.com>
To:     <broonie@...nel.org>
CC:     <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <git@...inx.com>,
        Karen Dombroski <karen.dombroski@...sbioimaging.com>,
        "Amit Kumar Mahapatra" <amit.kumar-mahapatra@...inx.com>
Subject: [RESEND 2/2] spi: spi-zynq-qspi: Fix stack violation bug

From: Karen Dombroski <karen.dombroski@...sbioimaging.com>

When the number of bytes for the op is greater than one, the read could
run off the end of the function stack and cause a crash.

This patch restores the behaviour of safely reading out of the original
opcode location.

Signed-off-by: Karen Dombroski <karen.dombroski@...sbioimaging.com>
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@...inx.com>
---
 drivers/spi/spi-zynq-qspi.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-zynq-qspi.c b/drivers/spi/spi-zynq-qspi.c
index 1acde9e24973..5a3d81c31d04 100644
--- a/drivers/spi/spi-zynq-qspi.c
+++ b/drivers/spi/spi-zynq-qspi.c
@@ -528,18 +528,17 @@ static int zynq_qspi_exec_mem_op(struct spi_mem *mem,
 	struct zynq_qspi *xqspi = spi_controller_get_devdata(mem->spi->master);
 	int err = 0, i;
 	u8 *tmpbuf;
-	u8 opcode = op->cmd.opcode;
 
 	dev_dbg(xqspi->dev, "cmd:%#x mode:%d.%d.%d.%d\n",
-		opcode, op->cmd.buswidth, op->addr.buswidth,
+		op->cmd.opcode, op->cmd.buswidth, op->addr.buswidth,
 		op->dummy.buswidth, op->data.buswidth);
 
 	zynq_qspi_chipselect(mem->spi, true);
 	zynq_qspi_config_op(xqspi, mem->spi);
 
-	if (op->cmd.nbytes) {
+	if (op->cmd.opcode) {
 		reinit_completion(&xqspi->data_completion);
-		xqspi->txbuf = &opcode;
+		xqspi->txbuf = (u8 *)&op->cmd.opcode;
 		xqspi->rxbuf = NULL;
 		xqspi->tx_bytes = op->cmd.nbytes;
 		xqspi->rx_bytes = op->cmd.nbytes;
-- 
2.17.1