[V2][PATCH 4/5] spi: spi-zynqmp-gqspi: fix use-after-free in zynqmp_qspi_exec_op

[quanyang . wang]

From: Quanyang Wang <quanyang.w...@windriver.com>

When handling op->addr, it is using the buffer "tmpbuf" which has been
freed. This will trigger a use-after-free KASAN warning. Let's use
temporary variables to store op->addr.val and op->cmd.opcode to fix
this issue.

Signed-off-by: Quanyang Wang <quanyang.w...@windriver.com>
---
 drivers/spi/spi-zynqmp-gqspi.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/spi-zynqmp-gqspi.c b/drivers/spi/spi-zynqmp-gqspi.c
index 2e2607b5dee9..419bc1e6358b 100644
--- a/drivers/spi/spi-zynqmp-gqspi.c
+++ b/drivers/spi/spi-zynqmp-gqspi.c
@@ -928,8 +928,9 @@ static int zynqmp_qspi_exec_op(struct spi_mem *mem,
        struct zynqmp_qspi *xqspi = spi_controller_get_devdata
                                    (mem->spi->master);
        int err = 0, i;
-       u8 *tmpbuf;
        u32 genfifoentry = 0;
+       u16 opcode = op->cmd.opcode;
+       u64 opaddr;
 
        dev_dbg(xqspi->dev, "cmd:%#x mode:%d.%d.%d.%d\n",
                op->cmd.opcode, op->cmd.buswidth, op->addr.buswidth,
@@ -942,14 +943,8 @@ static int zynqmp_qspi_exec_op(struct spi_mem *mem,
        genfifoentry |= xqspi->genfifobus;
 
        if (op->cmd.opcode) {
-               tmpbuf = kzalloc(op->cmd.nbytes, GFP_KERNEL | GFP_DMA);
-               if (!tmpbuf) {
-                       mutex_unlock(&xqspi->op_lock);
-                       return -ENOMEM;
-               }
-               tmpbuf[0] = op->cmd.opcode;
                reinit_completion(&xqspi->data_completion);
-               xqspi->txbuf = tmpbuf;
+               xqspi->txbuf = &opcode;
                xqspi->rxbuf = NULL;
                xqspi->bytes_to_transfer = op->cmd.nbytes;
                xqspi->bytes_to_receive = 0;
@@ -963,13 +958,12 @@ static int zynqmp_qspi_exec_op(struct spi_mem *mem,
                if (!wait_for_completion_timeout
                    (&xqspi->data_completion, msecs_to_jiffies(1000))) {
                        err = -ETIMEDOUT;
-                       kfree(tmpbuf);
                        goto return_err;
                }
-               kfree(tmpbuf);
        }
 
        if (op->addr.nbytes) {
+               xqspi->txbuf = &opaddr;
                for (i = 0; i < op->addr.nbytes; i++) {
                        *(((u8 *)xqspi->txbuf) + i) = op->addr.val >>
                                        (8 * (op->addr.nbytes - i - 1));
-- 
2.25.1