[PATCH] spi: rspi: Fixes bogus received byte and replaces "n" by "len" in commit 3be09be

[DongCV <cv-dong@xxxxxxxxxxx>]

In qspi_transfer_in(), when receiving the last n (or len) bytes of data,
1 bogus byte was written in the receive buffer.
This code leads to a buffer overflow.

"jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x03b40000: 0x1900 instead
 jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x03b40004: 0x000c instead"

The error message above happens when trying to mount, unmount, and remount a jffs2-formatted device.
This patch removed the bogus write and for clearer to use, here replaced "n" by "len" in
qspi_transfer_in() and qspi_transfer_out() to fixes: 3be09bec42a800d4
"spi: rspi: supports 32bytes buffer for DUAL and QUAD"

Here is Geert's comments:

"May I suggest the following:

    spi: rspi: Fix bogus received byte in qspi_transfer_in()

    When there are less than QSPI_BUFFER_SIZE remaining bytes to be received,
    qspi_transfer_in() writes one bogus byte in the receive buffer, possibly
    leading to a buffer overflow.

    This can be reproduced by mounting, unmounting, and remounting a
    jffs2-formatted device, causing lots of warnings like:

        jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found
at 0x03b40000: 0x1900 instead

    Remove the bogus write to fix this.

It's also a good idea to add a Fixes tag:

    Fixes: 3be09bec42a800d4 ("spi: rspi: supports 32bytes buffer for
DUAL and QUAD")

(the code was moved afterwards, but both the origin and the move were
 integrated in v4.10-rc1)."

Signed-off-by: DongCV <cv-dong@xxxxxxxxxxx>

Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
 drivers/spi/spi-rspi.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
index 9daf500..bc3c868 100644
--- a/drivers/spi/spi-rspi.c
+++ b/drivers/spi/spi-rspi.c
@@ -808,7 +808,7 @@ static int qspi_transfer_out(struct rspi_data *rspi, struct spi_transfer *xfer)
 			for (i = 0; i < len; i++)
 				rspi_write_data(rspi, *tx++);
 		} else {
-			ret = rspi_pio_transfer(rspi, tx, NULL, n);
+			ret = rspi_pio_transfer(rspi, tx, NULL, len);
 			if (ret < 0)
 				return ret;
 		}
@@ -845,10 +845,9 @@ static int qspi_transfer_in(struct rspi_data *rspi, struct spi_transfer *xfer)
 			for (i = 0; i < len; i++)
 				*rx++ = rspi_read_data(rspi);
 		} else {
-			ret = rspi_pio_transfer(rspi, NULL, rx, n);
+			ret = rspi_pio_transfer(rspi, NULL, rx, len);
 			if (ret < 0)
 				return ret;
-			*rx++ = ret;
 		}
 		n -= len;
 	}
-- 
1.9.1

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