linux-kernel - [PATCH 4.18 40/88] mtd: devices: m25p80: Make sure the buffer passed in op is DMA-able

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Message-Id: <20180927090305.611960984@linuxfoundation.org>
Date:   Thu, 27 Sep 2018 11:03:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>
Subject: [PATCH 4.18 40/88] mtd: devices: m25p80: Make sure the buffer passed in op is DMA-able

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Boris Brezillon <boris.brezillon@...tlin.com>

commit 4a3e85f2674cbfb81052059107d0165269778e2f upstream.

As documented in spi-mem.h, spi_mem_op->data.buf.{in,out} must be
DMA-able, and commit 4120f8d158ef ("mtd: spi-nor: Use the spi_mem_xx()
API") failed to follow this rule as buffers passed to
->{read,write}_reg() are usually placed on the stack.

Fix that by allocating a scratch buffer and copying the data around.

Fixes: 4120f8d158ef ("mtd: spi-nor: Use the spi_mem_xx() API")
Reported-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@...tlin.com>
Tested-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mtd/devices/m25p80.c |   26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -41,13 +41,23 @@ static int m25p80_read_reg(struct spi_no
 	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(code, 1),
 					  SPI_MEM_OP_NO_ADDR,
 					  SPI_MEM_OP_NO_DUMMY,
-					  SPI_MEM_OP_DATA_IN(len, val, 1));
+					  SPI_MEM_OP_DATA_IN(len, NULL, 1));
+	void *scratchbuf;
 	int ret;
 
+	scratchbuf = kmalloc(len, GFP_KERNEL);
+	if (!scratchbuf)
+		return -ENOMEM;
+
+	op.data.buf.in = scratchbuf;
 	ret = spi_mem_exec_op(flash->spimem, &op);
 	if (ret < 0)
 		dev_err(&flash->spimem->spi->dev, "error %d reading %x\n", ret,
 			code);
+	else
+		memcpy(val, scratchbuf, len);
+
+	kfree(scratchbuf);
 
 	return ret;
 }
@@ -58,9 +68,19 @@ static int m25p80_write_reg(struct spi_n
 	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(opcode, 1),
 					  SPI_MEM_OP_NO_ADDR,
 					  SPI_MEM_OP_NO_DUMMY,
-					  SPI_MEM_OP_DATA_OUT(len, buf, 1));
+					  SPI_MEM_OP_DATA_OUT(len, NULL, 1));
+	void *scratchbuf;
+	int ret;
+
+	scratchbuf = kmemdup(buf, len, GFP_KERNEL);
+	if (!scratchbuf)
+		return -ENOMEM;
 
-	return spi_mem_exec_op(flash->spimem, &op);
+	op.data.buf.out = scratchbuf;
+	ret = spi_mem_exec_op(flash->spimem, &op);
+	kfree(scratchbuf);
+
+	return ret;
 }
 
 static ssize_t m25p80_write(struct spi_nor *nor, loff_t to, size_t len,