linux-kernel - [PATCH] spi: spi-mem: check if data buffers are on stack

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Date:   Mon, 31 Jan 2022 17:15:08 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     Mark Brown <broonie@...nel.org>
CC:     Pratyush Yadav <p.yadav@...com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Michael Walle <michael@...le.cc>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Takahiro Kuwano <tkuw584924@...il.com>,
        <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] spi: spi-mem: check if data buffers are on stack

The buffers passed in the data phase must be DMA-able. Programmers often
don't realise this requirement and pass in buffers that reside on the
stack. This can be hard to spot when reviewing code. Reject ops if their
data buffer is on the stack to avoid this.

Signed-off-by: Pratyush Yadav <p.yadav@...com>
---
 drivers/spi/spi-mem.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 37f4443ce9a0..b3793a2979ee 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -207,6 +207,15 @@ static int spi_mem_check_op(const struct spi_mem_op *op)
 	    !spi_mem_buswidth_is_valid(op->data.buswidth))
 		return -EINVAL;
 
+	/* Buffers must be DMA-able. */
+	if (op->data.dir == SPI_MEM_DATA_IN &&
+	    object_is_on_stack(op->data.buf.in))
+		return -EINVAL;
+
+	if (op->data.dir == SPI_MEM_DATA_OUT &&
+	    object_is_on_stack(op->data.buf.out))
+		return -EINVAL;
+
 	return 0;
 }
 
-- 
2.34.1