mtd: devices: m25p80: Make sure the buffer passed in op is DMA-able

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@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>

1 files changed, 23 insertions, 3 deletions

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index cbfafc453274..270d3c9580c5 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -39,13 +39,23 @@ static int m25p80_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
         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;
 }
@@ -56,9 +66,19 @@ static int m25p80_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
         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;
 
-        return spi_mem_exec_op(flash->spimem, &op);
+        scratchbuf = kmemdup(buf, len, GFP_KERNEL);
+        if (!scratchbuf)
+                return -ENOMEM;
+
+        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,