Messages in this thread | | | Date | Mon, 29 Jun 2020 15:01:37 +0100 | From | Lee Jones <> | Subject | Re: [PATCH 4/5] mfd: sprd-sc27xx-spi: Fix divide by zero when allocating register offset/mask |
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On Mon, 29 Jun 2020, Johan Hovold wrote:
> On Mon, Jun 29, 2020 at 01:32:14PM +0100, Lee Jones wrote: > > Since ddata->irqs[] is already zeroed when allocated by devm_kcalloc() and > > dividing 0 by anything is still 0, there is no need to re-assign > > ddata->irqs[i].* values. Instead, it should be safe to begin at 1. > > > > This fixes the following W=1 warning: > > > > drivers/mfd/sprd-sc27xx-spi.c:255 sprd_pmic_probe() debug: sval_binop_unsigned: divide by zero > > > > Cc: Orson Zhai <orsonzhai@gmail.com> > > Cc: Baolin Wang <baolin.wang7@gmail.com> > > Cc: Chunyan Zhang <zhang.lyra@gmail.com> > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > --- > > drivers/mfd/sprd-sc27xx-spi.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/mfd/sprd-sc27xx-spi.c b/drivers/mfd/sprd-sc27xx-spi.c > > index c305e941e435c..694a7d429ccff 100644 > > --- a/drivers/mfd/sprd-sc27xx-spi.c > > +++ b/drivers/mfd/sprd-sc27xx-spi.c > > @@ -251,7 +251,7 @@ static int sprd_pmic_probe(struct spi_device *spi) > > return -ENOMEM; > > > > ddata->irq_chip.irqs = ddata->irqs; > > - for (i = 0; i < pdata->num_irqs; i++) { > > + for (i = 1; i < pdata->num_irqs; i++) { > > ddata->irqs[i].reg_offset = i / pdata->num_irqs; > > ddata->irqs[i].mask = BIT(i % pdata->num_irqs); > > } > > This doesn't look right either. > > First, the loop is never executed if num_irqs is zero.
The point of the patch is that 0 entries are never processed.
However, what I appear to have overlooked is that BIT(0 % x) is not 0, it's 1.
> Second, the current code looks bogus too as reg_offset is always set to > zero and mask to BIT(i)...
Heh. I wonder if/how this was tested.
I'm going to wait to hear from the authors before attempting to fix this again.
Baolin, Could you please clarify this for us please?
-- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog
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