Re: [PATCH] mtd: spi-nor: stm32-quadspi: Fix uninitialized error return code

From: Ludovic BARRE
Date: Fri Sep 15 2017 - 06:07:48 EST




On 07/17/2017 12:22 PM, Geert Uytterhoeven wrote:
Hi Ludovic,

On Mon, Jul 17, 2017 at 11:56 AM, Ludovic BARRE <ludovic.barre@xxxxxx> wrote:
Today only write_reg could be call with len=0 (spi-nor.c:
write_enable/disable, set_4byte, erase_chip)

But your remark make sense to prevent: gcc warning and framework evolution
...


-In stm32-quadspi.c transfer data is enabled if tx_data is true (some
actions under this bool)

stm32_qspi_write_reg has already this protection with "!!(buf && len > 0);"

but we could extend this protection

- cmd.tx_data = true;
+ cmd.tx_data = !!(len > 0);

In : stm32_qspi_read, stm32_qspi_write, stm32_qspi_read_reg

Ah, I missed the check for !cmd->tx_data at the top of stm32_qspi_tx()

-And to avoid gcc warning: I prefer initialize "ret" in the beginning of
function

- int ret;
+ int ret = 0;

I tested this changes, and it's ok for me.

Geert could you resend a new version, or do you prefer that I take care of
it

If you initialized ret at the beginning, you lose the ability to catch newly
introduced similar bugs in the future.
like discuss in thread https://patchwork.kernel.org/patch/9952849/ with Arnd and Geert

Cyrille, Marek: could you take geert patch and abandon
https://patchwork.kernel.org/patch/9952849/
thanks

Acked-by: Ludovic Barre <ludovic.barre@xxxxxx>


On 07/15/2017 10:00 AM, Geert Uytterhoeven wrote:

With gcc 4.1.2:

drivers/mtd/spi-nor/stm32-quadspi.c: In function
âstm32_qspi_tx_pollâ:
drivers/mtd/spi-nor/stm32-quadspi.c:230: warning: âretâ may be used
uninitialized in this function

Indeed, if stm32_qspi_cmd.len is zero, ret will be uninitialized.
This length is passed from outside the driver using the
spi_nor.{read,write}{,_reg}() callbacks.

Several functions in drivers/mtd/spi-nor/spi-nor.c (e.g. write_enable(),
write_disable(), and erase_chip()) call spi_nor.write_reg() with a zero
length.

Fix this by returning an explicit zero on success.

Fixes: 0d43d7ab277a048c ("mtd: spi-nor: add driver for STM32 quad spi
flash controller")
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
drivers/mtd/spi-nor/stm32-quadspi.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c
b/drivers/mtd/spi-nor/stm32-quadspi.c
index 86c0931543c538c3..ad6a3e1844cbe5ec 100644
--- a/drivers/mtd/spi-nor/stm32-quadspi.c
+++ b/drivers/mtd/spi-nor/stm32-quadspi.c
@@ -240,12 +240,12 @@ static int stm32_qspi_tx_poll(struct stm32_qspi
*qspi,

STM32_QSPI_FIFO_TIMEOUT_US);
if (ret) {
dev_err(qspi->dev, "fifo timeout (stat:%#x)\n",
sr);
- break;
+ return ret;
}
tx_fifo(buf++, qspi->io_base + QUADSPI_DR);
}
- return ret;
+ return 0;
}
static int stm32_qspi_tx_mm(struct stm32_qspi *qspi,

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds